Maternally inherited diabetes and deafness: a multicenter study

Neovascular Glaucoma in MELAS syndrome

Purpose

To describe examination and findings in a case of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) with particular focus on the ocular sequelae from diabetes.

Observations

Neovascular glaucoma is not a common manifestation of MELAS.

Conclusions and Importance

We present a rare case of neovascular glaucoma in a patient with MELAS with a history of diabetes, hearing loss, and macular dystrophy. MELAS should be suspected in patients with this constellation of symptoms.

Ocular manifestations of the genetic causes of focal and segmental glomerulosclerosis

Genetic forms of focal and segmental glomerulosclerosis (FSGS) often have extra-renal manifestations. This study examined FSGS-associated genes from the Genomics England Renal proteinuria panel for reported and likely ocular features. Thirty-two of the 55 genes (58%) were associated with ocular abnormalities in human disease, and a further 12 (22%) were expressed in the retina or had an eye phenotype in mouse models. The commonest genes affected in congenital nephrotic syndrome (NPHS1, NPHS2, WT1, LAMB2, PAX2 but not PLCE1) may have ocular manifestations . Many genes affected in childhood-adolescent onset FSGS (NPHS1, NPHS2, WT1, LAMB2, SMARCAL1, NUP107 but not TRPC6 or PLCE1) have ocular features. The commonest genes affected in adult-onset FSGS (COL4A3-COL4A5, GLA ) have ocular abnormalities but not the other frequently affected genes (ACTN4, CD2AP, INF2, TRPC6). Common ocular associations of genetic FSGS include cataract, myopia, strabismus, ptosis and retinal atrophy. Mitochondrial forms of FSGS (MELAS, MIDD, Kearn's Sayre disease) are associated with retinal atrophy and inherited retinal degeneration. Some genetic kidney diseases (CAKUT, ciliopathies, tubulopathies) that result in secondary forms of FSGS also have ocular features. Ocular manifestations suggest a genetic basis for FSGS, often help identify the affected gene, and prompt genetic testing. In general, ocular abnormalities require early evaluation by an ophthalmologist, and sometimes, monitoring or treatment to improve vision or prevent visual loss from complications. In addition, the patient should be examined for other syndromic features and first degree family members assessed.

Endocrine features of primary mitochondrial diseases

PURPOSE OF REVIEW

Primary mitochondrial diseases are one of the most prevalent groups of multisystem genetic disorders. Endocrinopathies associated with mitochondrial diseases may have clinical features that are distinct from the more common forms. We provide an overview of mitochondrial disorder genetics and phenotypes, focusing on recent studies regarding identification and treatment of associated endocrinopathies.

RECENT FINDINGS

Known endocrine phenotypes of mitochondrial disorders continue to expand, and now include growth hormone deficiency, hypogonadism, precocious puberty, hypoparathyroidism, hypo- and hyperthyroidism, diabetes, and adrenal insufficiency. Recent studies suggest several genotype-phenotype correlations, including those related to nuclear variants. Diagnosis is important, as special considerations should be made in the management of endocrinopathies in mitochondrial patients. Finally, new mitochondrial replacement strategies may soon be available for women interested in preventing mitochondrial disease transmission to offspring.

SUMMARY

Patients with multiple endocrinopathies or atypical endocrinopathies should be evaluated for primary mitochondrial disease, as a diagnosis may impact management of these individuals.

Identification of eight genomic protective alleles for mitochondrial diabetes by Kinship-graph convolutional network

AIMS

Nearly 85% of maternally inherited diabetes and deafness (MIDD) are caused by the m.3243A>G mutation in the mitochondrial DNA. However, the clinical phenotypes of MIDD may also be influenced by the nuclear genome, this study aimed to investigate nuclear genome variants that influence clinical phenotypes associated with m.3243A>G mutation in MIDD based on whole-genome sequencing of the patients belonging to pedigrees.

MATERIALS AND METHODS

We analyzed a whole-genome sequencing (WGS) dataset from blood samples of 38 MIDD patients with the m.3243A > G mutation belonging to 10 pedigrees, by developing a Kinship-graph convolutional network approach, called Ki-GCN, integrated with the conventional genome-wide association study (GWAS) methods.

RESULTS

We identified eight protective alleles in the nuclear genome that have protective effects against the onset of MIDD, related deafness, and also type 2 diabetes. Based on these eight protective alleles, we constructed an effective logistic regression model to predict the early or late onset of MIDD patients.

CONCLUSIONS

There are protective alleles in the nuclear genome that are associated with the onset-age of MIDD patients and might also provide protective effects on the deafness derived from MIDD patients.

Multimodal analysis in symptomatic MIDD-associated retinopathy. A case report and literature review

Purpose

To present results of contemporary multimodal ophthalmic imaging in a case of maternally inherited diabetes and deafness (MIDD) and a literature review of MIDD.

Methods

A case of a 47-year-old female with diabetes mellitus, severe insulin resistance, familial lipodystrohy, deafness and increasing problems with vision is reported. A full ophthalmic examination was done, including best corrected visual acuity (BCVA, LogMAR), funduscopy, and imaging studies: optical coherence tomography (OCT), OCT angiography (OCT-A), fundus autofloresence (FAF), visual fields (HVF) 10-2 , electrophysiology (EP) and genetic testing were performed. Literature available on the topic was reviewed.

Results

BCVA was 0.06 LogMAR in the right eye and 0.1 LogMAR in the left. Funduscopy revealed atrophy (AT) and pigmentary changes but no diabetic retinopathy. HVF confirmed corresponding defects. The imaging and diagnostic tests showed the following abnormalities: FAF: hypoautofluoresence in areas of AT and mottled appearance in the macular and peripapillary area; OCT: attenuation of outer retinal layers and retinal pigment epithelium (RPE) in the AT; OCT-A: thinning of the deep capillary plexus and choriocapillaris; EP: abnormalities on full field electroretinogram (ERG), 30 Hz flicker and single cone flash response; multifocal ERG: reduced responses; genetic testing: A-to-G transition mutation at position 3243 of the mitochondrial genome, typical for MIDD. After one year OCT ganglion cell analysis showed loss of thickness.

Conclusions

Genetic testing should be considered in diabetic patients with pigmentary retinopathy. Imaging studies and diagnostic testing showed structural and functional retinal changes, confined to the macula and progressive in nature.

Imeglimin-mediated glycemic control in maternally inherited deafness and diabetes

Mitochondrial dysfunction causes maternally inherited deafness and diabetes (MIDD). Herein, we report improved glycemic control in a 47-year-old Japanese woman with MIDD using imeglimin without major adverse effects. Biochemical tests and metabolome analysis were performed before and after imeglimin administration. Blood glucose level fluctuations were determined. Sulfonylureas, dipeptidyl peptidase-4 inhibitors (DPP4is), and sodium glucose transporter-2 inhibitors (SGLT2i) were administered to evaluate the efficacy of their combination with imeglimin. Imeglimin decreased the HbA1c and ammonia levels and increased the time-in-range, C-peptide reactivity, and glucagon level. Elevated citrulline and histamine levels were decreased by imeglimin. The hypoglycemic effect was not enhanced by imeglimin when combined with sulfonylurea or DPP4i, but the blood glucose level was improved when combined with SGLT2i. Imeglimin improved glucose concentration-dependent insulin secretion and maximized the insulin secretory capacity by improving mitochondrial function and glutamine metabolism and urea circuit abnormalities by promoting glucagon secretion. Imeglimin could improve glycemic control in MIDD.

Imeglimin-mediated glycemic control in maternally inherited deafness and diabetes

Mitochondrial dysfunction causes maternally inherited deafness and diabetes (MIDD). Herein, we report improved glycemic control in a 47-year-old Japanese woman with MIDD using imeglimin without major adverse effects. Biochemical tests and metabolome analysis were performed before and after imeglimin administration. Blood glucose level fluctuations were determined. Sulfonylureas, dipeptidyl peptidase-4 inhibitors (DPP4is), and sodium glucose transporter-2 inhibitors (SGLT2i) were administered to evaluate the efficacy of their combination with imeglimin. Imeglimin decreased the HbA1c and ammonia levels and increased the time-in-range, C-peptide reactivity, and glucagon level. Elevated citrulline and histamine levels were decreased by imeglimin. The hypoglycemic effect was not enhanced by imeglimin when combined with sulfonylurea or DPP4i, but the blood glucose level was improved when combined with SGLT2i. Imeglimin improved glucose concentration-dependent insulin secretion and maximized the insulin secretory capacity by improving mitochondrial function and glutamine metabolism and urea circuit abnormalities by promoting glucagon secretion. Imeglimin could improve glycemic control in MIDD.

Clinical Approaches for Mitochondrial Diseases

Mitochondria are subcontractors dedicated to energy production within cells. In human mitochondria, almost all mitochondrial proteins originate from the nucleus, except for 13 subunit proteins that make up the crucial system required to perform 'oxidative phosphorylation (OX PHOS)', which are expressed by the mitochondria's self-contained DNA. Mitochondrial DNA (mtDNA) also encodes 2 rRNA and 22 tRNA species. Mitochondrial DNA replicates almost autonomously, independent of the nucleus, and its heredity follows a non-Mendelian pattern, exclusively passing from mother to children. Numerous studies have identified mtDNA mutation-related genetic diseases. The consequences of various types of mtDNA mutations, including insertions, deletions, and single base-pair mutations, are studied to reveal their relationship to mitochondrial diseases. Most mitochondrial diseases exhibit fatal symptoms, leading to ongoing therapeutic research with diverse approaches such as stimulating the defective OXPHOS system, mitochondrial replacement, and allotropic expression of defective enzymes. This review provides detailed information on two topics: (1) mitochondrial diseases caused by mtDNA mutations, and (2) the mechanisms of current treatments for mitochondrial diseases and clinical trials.

Inherited causes of combined vision and hearing loss: clinical features and molecular genetics

Combined vision and hearing loss, also known as dual sensory impairment, can occur in several genetic conditions, including ciliopathies such as Usher and Bardet-Biedl syndrome, mitochondrial DNA disorders and systemic diseases, such as CHARGE, Stickler, Waardenburg, Alport and Alstrom syndrome. The retinal phenotype may point to the diagnosis of such disorders. Herein, we aim to provide a comprehensive review of the molecular genetics and clinical features of the most common non-chromosomal inherited disorders to cause dual sensory impairment.

Mitochondria and the eye-manifestations of mitochondrial diseases and their management

Historically, distinct mitochondrial syndromes were recognised clinically by their ocular features. Due to their predilection for metabolically active tissue, mitochondrial diseases frequently involve the eye, resulting in a range of ophthalmic manifestations including progressive external ophthalmoplegia, retinopathy and optic neuropathy, as well as deficiencies of the retrochiasmal visual pathway. With the wider availability of genetic testing in clinical practice, it is now recognised that genotype-phenotype correlations in mitochondrial diseases can be imprecise: many classic syndromes can be associated with multiple genes and genetic variants, and the same genetic variant can have multiple clinical presentations, including subclinical ophthalmic manifestations in individuals who are otherwise asymptomatic. Previously considered rare diseases with no effective treatments, considerable progress has been made in our understanding of mitochondrial diseases with new therapies emerging, in particular, gene therapy for inherited optic neuropathies.

Maternally Inherited Diabetes and Deafness (MIDD) - Atypical Clinical Diabetes Features Leading to the Diagnosis

Maternally inherited diabetes and deafness (MIDD) syndrome refers to a rarely diagnosed disorder caused by pathogenic variants in mtDNA. It was first identified in 1992 and, to date, is considered underdiagnosed because of misclassification to type 1 or type 2 diabetes mellitus. MIDD reflects a multisystem metabolic syndrome commonly resulting in insulin-requiring diabetes and sensorineural deafness but can also lead to a broad range of other manifestations. The spectrum of pathology differs among individuals, likely because of varied degrees of heteroplasmy associated with mtDNA. Heteroplasmy also creates diagnostic difficulties, with a high index of suspicion required to diagnose MIDD in some cases. Here, we review a patient with MIDD who presented with an atypical clinical diabetes picture, additionally documenting his pedigree. To our knowledge, this is the first Cypriot reported with MIDD.

Pilot Trial on the Effect of 5-Aminolevulinic Acid on Glucose Tolerance in Patients with Maternally Inherited Diabetes and Deafness

INTRODUCTION

The amino acid 5-aminolevulinic acid (5-ALA) is the first heme biosynthetic precursor. The combination of 5-ALA with sodium ferrous citrate (SFC) enhances heme production, leading to increased adenosine triphosphate (ATP) production in mitochondria. We investigated whether administering 5-ALA/SFC improves glucose tolerance with an increase in insulin secretion in patients with maternally inherited diabetes and deafness (MIDD), which is characterized by an insulin secretory disorder due to impaired mitochondrial ATP production.

METHODS

This was a single-arm, open-label, interventional study. We prospectively administered the oral glucose tolerance test (OGTT) twice in five patients with MIDD who had received intensive insulin therapy: before and 24 weeks after an administration of 5-ALA/SFC (200/232 mg per day). We measured the concentrations of glucose, insulin, C-peptide, and proinsulin at fasting, and 30, 60, and 120 min after glucose load in each OGTT. The primary endpoint was the changes in the area under the curve (AUC) of serum insulin from 0 to 120 min during OGTT from baseline to 24 weeks.

RESULTS

The serum insulin AUC (µU/mL) during the 120-min OGTT tended to increase from baseline to 24 weeks but not significantly (17.1 ± 13.7 versus 22.3 ± 13.4, p = 0.077). The plasma glucose AUC (mg/dL) during the 120-min OGTT at 24 weeks was not significantly decreased; the late phase of glucose excursion from 60 to 120 min was significantly decreased compared with baseline (357 ± 42 versus 391 ± 50, p = 0.041). The mean level of glycated hemoglobin (HbA1c) decreased from 8.3 ± 1.2% at baseline to 7.9 ± 0.3% at 24 weeks (p = 0.36) without increasing the daily dose of insulin injections.

CONCLUSION

The 24-week administration of 5-ALA/SFC did not demonstrate a significant improvement in insulin secretion in patients with MIDD. Further investigations with a larger number of patients and a placebo control group are required to clarify the potential efficacy of 5-ALA/SFC for ameliorating mitochondrial dysfunctions in MIDD.

TRIAL REGISTRATION

UMIN-CTR000040581 and jRCT071200025.

A Multisystem Mitochondrial Disease Caused by a Novel MT-TL1 mtDNA Variant: A Case Report

BACKGROUND

Mitochondrial tRNA (MTT) genes are hotspot for mitochondrial DNA mutation and are responsible of half mitochondrial disease. MTT mutations are associated with a broad spectrum of phenotype often with complex multisystem involvement and complex genotype-phenotype correlations. MT-TL1 mutations, among which the m.3243A>G mutation is the most frequent, are associated with myopathy, maternal inherited diabetes and deafness, MELAS, cardiomyopathy, and focal segmental glomerulosclerosis.

CASE STUDY

Here we report the case of an Italian 49-years old female presenting with encephalomyopathy, chronic proteinuric kidney disease and a new heteroplasmic m.3274_3275delAC MT-TL1 gene mutation.

CONCLUSIONS

Our case demonstrates a systemic mitochondrial disease caused by the heteroplasmic m.3274_3275delAC MT-TL1 gene mutation, not yet described in the literature. A mitochondrial disease should be suspected in case of complex multisystem phenotypes, including steroid-resistant nephrotic syndrome with multisystemic involvement.

Bone Deformities and Kidney Failure: Coincidence of PHEX-Related Hypophosphatemic Rickets and m.3243A>G Mitochondrial Disease

X-linked hypophosphatemic rickets (XLH) and m.3243A>G mitochondrial disease share several clinical findings, including short stature, hearing impairment (HI), nephropathy, and hypertension. Here, we report on a case with the rare coincidence of these two genetic conditions. In early childhood, the patient presented with hypophosphatemia and bone deformities and was clinically diagnosed with XLH. This was genetically verified in adulthood with the identification of a de novo pathogenic deletion in phosphate-regulating endopeptidase homolog X-linked (PHEX). In addition, the patient developed HI and hypertension and when his mother was diagnosed with m.3243A>G, subsequent genetic testing confirmed the patient to carry the same variant. Over the next two decades, the patient developed progressive renal impairment however without nephrocalcinosis known to associate with XLH which could indicate an m.3243A>G-related kidney disease. Parallel with the progression of renal impairment, the patient developed hyperphosphatemia and secondary hyperparathyroidism. In conclusion, this case represents a complex clinical phenotype with the reversal of hypo- to hyperphosphatemia in XLH potentially mediated by the development of an m.3243A>G-associated nephropathy.

Renal involvement is frequent in adults with primary mitochondrial disorders: an observational study

Background

Mitochondrial functions are controlled by genes of both mitochondrial and nuclear DNA. Pathogenic variants affecting any of these are responsible for primary mitochondrial disorders (MIDs), which can be diagnosed during adulthood. Kidney functions are highly dependent on mitochondrial respiration. However, the prevalence of MID-associated nephropathies (MIDANs) is unknown in the adult population. We aimed to address this point and to provide a full characterization of MIDANs in this population.

Methods

We retrospectively included for observational study adults (≥16 years of age) with genetically diagnosed MID between 2000 and 2020 in our tertiary care academic centre when they had a chronic kidney disease (CKD) evaluation. MIDANs were ascertained by CKD occurring in MIDs. The phenotypic, biological, histopathological and genotypic characteristics were recorded from the medical charts.

Results

We included 80 MID-affected adults and ascertained MIDANs in 28/80 (35%). Kidney diseases under the care of a nephrologist occurred in only 14/28 (50%) of the adults with MIDAN. MIDANs were tubulointerstitial nephropathy in 14/28 patients (50%) and glomerular diseases in 9/28 (32.1%). In adults with MID, MIDAN was negatively associated with higher albumin levels {odds ratio [OR] 0.79 [95% confidence interval (CI) 0.67-0.95]} and vision abnormalities [OR 0.17 (95% CI 0.03-0.94)] and positively associated with hypertension [OR 4.23 (95% CI 1.04-17.17)].

Conclusion

MIDANs are frequent among adult MIDs. They are mostly represented by tubulointerstitial nephropathy or glomerular disease. Vision abnormalities, hypertension and albumin levels were independently associated with MIDANs. Our results pave the way for prospective studies investigating the prevalence of MIDANs among undetermined kidney disease populations.

Macular findings expedite accurate diagnosis of MIDD in a young female patient with newly diagnosed diabetes

Purpose

To report a case of a 34-year-old female patient with newly diagnosed Maternally Inherited Diabetes and Deafness (MIDD) in the setting of undifferentiated macular dystrophy and newly discovered diabetes.

Observations

A 34-year-old woman presented to the retina service with new-onset diabetes and a history of hydroxychloroquine use. Ophthalmologic examination showed findings early in the patient's presentation that within the context of her recent diabetes diagnosis and family history pointed to MIDD as the specific cause of the patient's many different symptoms. This diagnosis was further supported through obtaining previous ophthalmic images of the patient's mother demonstrating circular areas of geographic atrophy seen in advanced MIDD, and the diagnosis was confirmed through genetic testing.

Conclusions and importance

As was observed in the patient discussed in this manuscript, recognition of macular dystrophy findings suggestive of MIDD can hasten a timely diagnosis for a patient with diabetes of unspecified etiology. Additionally, knowledge of the underlying cause being MIDD can optimize care for patients in terms of treatment, understanding their risk for various diabetes complications, screening for additional systemic manifestations, and initiating valuable genetic counseling for patients and their families. Given these factors and the surprisingly high prevalence of MIDD among diabetes patients, increased awareness of MIDD and its manifestations can help to optimize diagnosis and management for these patients.

Endocrine Manifestations and New Developments in Mitochondrial Disease

Mitochondrial diseases are a group of common inherited diseases causing disruption of oxidative phosphorylation. Some patients with mitochondrial disease have endocrine manifestations, with diabetes mellitus being predominant but also include hypogonadism, hypoadrenalism, and hypoparathyroidism. There have been major developments in mitochondrial disease over the past decade that have major implications for all patients. The collection of large cohorts of patients has better defined the phenotype of mitochondrial diseases and the majority of patients with endocrine abnormalities have involvement of several other systems. This means that patients with mitochondrial disease and endocrine manifestations need specialist follow-up because some of the other manifestations, such as stroke-like episodes and cardiomyopathy, are potentially life threatening. Also, the development and follow-up of large cohorts of patients means that there are clinical guidelines for the management of patients with mitochondrial disease. There is also considerable research activity to identify novel therapies for the treatment of mitochondrial disease. The revolution in genetics, with the introduction of next-generation sequencing, has made genetic testing more available and establishing a precise genetic diagnosis is important because it will affect the risk for involvement for different organ systems. Establishing a genetic diagnosis is also crucial because important reproductive options have been developed that will prevent the transmission of mitochondrial disease because of mitochondrial DNA variants to the next generation.

The application of precision medicine in monogenic diabetes

INTRODUCTION

Monogenic diabetes, a form of diabetes mellitus, is caused by a mutation in a single gene and may account for 1-2% of all clinical forms of diabetes. To date, more than 40 loci have been associated with either isolated or syndromic monogenic diabetes.

AREAS COVERED

While the request of a genetic test is mandatory for cases with diabetes onset in the first 6 months of life, a decision may be difficult for childhood or adolescent diabetes. In an effort to assist the clinician in this task, we have grouped monogenic diabetes genes according to the age of onset (or incidental discovery) of hyperglycemia and described the additional clinical features found in syndromic diabetes. The therapeutic options available are reviewed.

EXPERT OPINION

Technical improvements in DNA sequencing allow for rapid, simultaneous analysis of all genes involved in monogenic diabetes, progressively shrinking the area of unsolved cases. However, the complexity of the analysis of genetic data requires close cooperation between the geneticist and the diabetologist, who should play a proactive role by providing a detailed clinical phenotype that might match a specific disease gene.

Gene Panel Sequencing of Patients With Monogenic Diabetes Brings to Light Genes Typically Associated With Syndromic Presentations

Gene panel sequencing (NGS) offers the possibility of analyzing rare forms of monogenic diabetes (MgD). To that end, 18 genes were analyzed in 1,676 patients referred for maturity-onset diabetes of the young genetic testing. Among the 307 patients with a molecular diagnosis of MgD, 55 (17.9%) had a mutation in a gene associated with a genetic syndrome. Of the patients with mutations, 8% (n = 25) carried the m.3243A>G variant associated with maternally inherited diabetes and deafness. At the time of referral very few had reported hearing loss or any other element of the typical syndromic presentation. Of the patients, 6% had mutation in HNF1B even though the typical extrapancreatic features were not known at the time of referral. Surprisingly, the third most prominent etiology in these rare forms was the WFS1 gene, accounting for 2.9% of the patients with pathogenic mutations (n = 9). None of them displayed a Wolfram syndrome presentation even though some features were reported in six of nine patients. To restrict the analysis of certain genes to patients with the respective specific phenotypes would be to miss those with partial presentations. These results therefore underlie the undisputable benefit of NGS strategies even though the situation implies cascade consequences both for the molecular biologist and for the clinician.

Neurological manifestations in m.3243A>G-related disease triggered by metformin

INTRODUCTION

m.3243A>G-related disease has multi-systemic manifestations including diabetes mellitus. It is uncertain whether metformin would trigger neurological manifestations of this disease. This study aims to review the diagnosis and management of m.3243A>G-related diabetes genetically confirmed by our laboratory and to evaluate the risk of metformin use triggering neurological manifestations.

METHODS

Cases with m.3243A>G detected between 2009 and 2020 were reviewed. Cases with diabetes mellitus were included. Cases with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) before diabetes onset were excluded. Odds ratio was calculated for association between metformin use and newly developed neurological manifestations.

RESULTS

Sixteen patients were identified. Odds ratio for metformin use was 3.50 [0.37-33.0; p = 0.3287]. One illustrative case with clear causal relationship between metformin use and neurological manifestations was described in detail.

CONCLUSION

m.3243A>G-related diabetes mellitus is underdiagnosed. Red flags including positive family history, short stature, low body weight and hearing loss are often overlooked. Early diagnosis allows regular systemic assessment. In the era of precision medicine and novel therapies, it is prudent to avoid metformin as it could trigger neurological manifestations in this condition. Coenzyme Q10, DPP-IV inhibitors, SGLT2 inhibitors and GLP-1 receptor agonists may be considered.

Chronic Intestinal Pseudo-obstruction with Mitochondrial Diseases

Chronic intestinal pseudo-obstruction (CIPO) is a rare disorder of intestinal dysmotility characterized by chronic symptoms, including vomiting and abdominal pain, associated with bowel obstruction without any mechanical obstructive causes. We herein report a case of mitochondrial diseases with recurrent duodenal obstruction that was initially diagnosed as superior mesenteric artery syndrome (SMAS) for a few years but was later diagnosed as CIPO. Since CIPO is known to be associated with mitochondrial diseases, it should be considered in the differential diagnosis of patients with mitochondrial diseases presenting with recurrent intestinal obstruction.

Mitochondrial Diabetes is Associated with tRNALeu(UUR) A3243G and ND6 T14502C Mutations

BACKGROUND

Mutations in mitochondrial DNA (mtDNA) are associated with type 2 diabetes mellitus (T2DM). In particular, m.A3243G is the most common T2DM-related mtDNA mutation in many families worldwide. However, the clinical features and pathophysiology of m.A3243G-induced T2DM are largely undefined.

METHODS

Two pedigrees with maternally inherited T2DM were underwent clinical, molecular and biochemical assessments. The mtDNA genes were PCR amplified and sequenced. Mitochondrial adenosine triphosphate (ATP) and reactive oxygen species (ROS) were measured in polymononuclear leukocytes derived from three patients with both the m.A3243G and m.T14502C mutations, three patients with only the m.A3243G mutation and three controls without these mutations. Moreover, GJB2, GJB3 and GJB6 mutations were screened by PCR-Sanger sequencing.

RESULTS

Members of the two pedigrees manifestated variable clinical phenotypes including diabetes and hearing and vision impairments. The age at onset of T2DM varied from 31 to 66 years, with an average of 41 years. Mutational analysis of mitochondrial genomes indicated the presence of the m.A3243G mutation in both pedigrees. Matrilineal relatives in one of the pedigrees harbored the coexisting of m.A3243G and m.T14502C mutations. Remarkably, the m.T14502C mutation, which causes the substitution of a conserved isoleucine for valine at position 58 in ND6 mRNA, may affect the mitochondrial respiratory chain functions. Biochemical analysis revealed that cell lines bearing both the m.A3243G and m.T14502C mutations exhibited greater reductions in ATP levels and increased ROS production compared with those carrying only the m.A3243G mutation. However, we did not find any mutations in the GJB2, GJB3 and GJB6 genes.

CONCLUSION

Our study indicated that mitochondrial diabetes is associated with the tRNA^Leu(UUR) A3243G and ND6 T14502C mutations.

The Mutations and Clinical Variability in Maternally Inherited Diabetes and Deafness: An Analysis of 161 Patients

Aims

To investigate the clinical features and mitochondrial mutations for maternally inherited diabetes and deafness.

Methods

PubMed, Embase, Medline, Web of Science, the China National Knowledge Infrastructure, and Wanfang were searched with the following search terms: "Maternally inherited diabetes and deafness" OR "MIDD" OR "Mitochondrial diabetes". The mutations and clinical features were analyzed. Correlation between the heteroplasmy levels of the m.3243A>G mutation in the peripheral blood and age at the onset of diabetes was conducted by Spearman test. The significance level was set as p < 0.05. Statistical analysis was performed using the Statistical Package for the Social Sciences version 26 for Windows.

Results

Totally 161 patients with 21 different mitochondrial mutations were enrolled. The most common mutation was the m.3243A>G mutation in 136 cases. Of 142 patients, 120 (84.51%) had family histories of diabetes or hearing loss. Hearing loss presented in 85.71% of the patients with mitochondrial mutations. Central nervous system diseases were found in 29.19%, myopathy in 22.98%, oculopathy in 23.60%, cardiac disease in 23.60%, and nephropathy in 13.66% of the patients. Forty-two of 101 (41.58%) patients were underweight. A significant negative correlation was found between the heteroplasmy levels of the m.3243A>G mutation in the peripheral blood and age at the onset of diabetes.

Conclusions

The young onset of diabetes with low or normal BMI, maternal inheritance, and presence of impairments of multiple systems should prompt a genetic testing in order to differentiate MIDD from other types of diabetes earlier.

Diabetes mellitus and hearing loss: A review

Diabetes (type 2) and sensorineural hearing loss are common health problems manifested with ageing. While both type 1 and type 2 diabetes have been associated with hearing loss, a causal link has been difficult to establish. Individuals with diabetes have twice the incidence of hearing loss compared to those without diabetes and those with prediabetes have a 30% higher rate of hearing loss. Whether hearing loss is associated with diabetes independent of glycemic control remains to be determined. Hearing loss has its own set of risk factors and shares others with diabetes. This review will summarize the complex relationship between diabetes and sensorineural hearing loss.

Hearing loss in inherited metabolic disorders: A systematic review

Inherited metabolic disorders (IMDs) have been observed in individuals with hearing loss (HL), but IMDs are rarely the cause of syndromic HL. With early diagnosis, management of HL is more effective and cortical reorganization is possible with hearing aids or cochlear implants. This review describes relationships between IMDs and HL in terms of incidence, etiology of HL, pathophysiology, and treatment. Forty types of IMDs are described in the literature, mainly in case reports. Management and prognosis are noted where existing. We also describe IMDs with HL given age of occurrence of HL. Reviewing the main IMDs that are associated with HL may provide an additional clinical tool with which to better diagnose syndromic HL.

The Role of Mitochondrial Dysfunction in Vascular Disease, Tumorigenesis, and Diabetes

Mitochondrial dysfunction is known to be associated with a wide range of human pathologies, such as cancer, metabolic, and cardiovascular diseases. One of the possible ways of mitochondrial involvement in the cellular damage is excessive production of reactive oxygen and nitrogen species (ROS and RNS) that cannot be effectively neutralized by existing antioxidant systems. In mitochondria, ROS and RNS can contribute to protein and mitochondrial DNA (mtDNA) damage causing failure of enzymatic chains and mutations that can impair mitochondrial function. These processes further lead to abnormal cell signaling, premature cell senescence, initiation of inflammation, and apoptosis. Recent studies have identified numerous mtDNA mutations associated with different human pathologies. Some of them result in imbalanced oxidative phosphorylation, while others affect mitochondrial protein synthesis. In this review, we discuss the role of mtDNA mutations in cancer, diabetes, cardiovascular diseases, and atherosclerosis. We provide a list of currently described mtDNA mutations associated with each pathology and discuss the possible future perspective of the research.

The Spectrum of Maculopathy in Mitochondrial DNA A3243G Mutation: A Case Series of Six Patients

BACKGROUND

The mitochondrial DNA (mtDNA) A3243G point mutation encompasses a heterogenous group of disorders including mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), maternally inherited diabetes and deafness (MIDD), and, rarely, chronic progressive external ophthalmoplegia (CPEO). Regardless of the clinical phenotype, a specific retinopathy has been associated with the presence of this mitochondrial DNA mutation. We present six female patients exhibiting retinopathy of the A3243G point mutation at various stages.

HISTORY AND SIGNS

Six female patients (37 - 70 years old) with the A3243G point mutation (four MELAS, one MIDD, and one CPEO) exhibited a maculopathy. Visual acuity ranged from 1/60 to 10/10. Visual field abnormalities varied from minimal decreased sensitivity to absolute central scotomas. They all exhibited, at various degrees, a characteristic pattern of perimacular and peripapillary retinal pigment epithelium (RPE) alterations, with mottled dys-autofluorescence and RPE atrophy and deposits on OCT.

THERAPY AND OUTCOME

The level of visual impairment depended on the foveal involvement and the extension of RPE atrophy. The severity of the maculopathy was not related to age. In the only long-term follow-up (15 years), evolution was slowly progressive.

CONCLUSIONS

A single mtDNA point mutation at locus 3243 can result in a variety of clinical presentations (MELAS, MIDD, or CPEO). Ocular involvement may manifest as a perimacular/peripapillary RPE atrophy/deposit, which can variably impact central visual function (from asymptomatic to legal blindness). The discovery of such a maculopathy should prompt the ophthalmologist to complete the personal and family history, namely, asking for the presence of diabetes mellitus and/or deafness.

Mitochondrial DNA A3243G variant-associated retinopathy: a meta-analysis of the clinical course of visual acuity and correlation with systemic manifestations

PURPOSE

The mitochondrial DNA A3243G (m.3243A>G) variant causes a wide spectrum of phenotypes, with pigmentary retinopathy as the most common ocular finding. We undertook this meta-analysis to investigate the clinical course of visual acuity (VA) in patients with m.3243A>G variant and provide key clinical correlations with systemic manifestations.

METHODS

A PubMed literature search was performed and studies were selected after satisfying pre-set inclusion criteria. Demographic and clinical data, including retinal findings and systemic manifestations were recorded. Cross-sectional and linear regression analyses were used to investigate the relationship between VA and age, as well as between the age at diagnosis of retinopathy and the mean ages at diagnosis of sensorineural hearing loss or diabetes. The age and prevalence of systemic manifestations among patients with and without retinopathy were studied using t-tests and Mann-Whitney U-tests (performed on binarized data). Likelihood ratios were computed.

RESULTS

The mean VA (average of both eyes) of 90 patients (72.2% female; 65/90) were collected from 18 studies published between 1990 and 2018. The baseline mean age was 45.2 years (range 17 to 92). The mean logMAR VA was 0.10 (- 0.12 to 1.39). There was a statistically significant linear correlation between the logMAR VA and age (p = .008). The VA of patients less than or equal to 50 years of age was significantly better than that of patients older than 50 years (0.06 vs.0.18 logMAR, p = .002). 67 patients (74.4%) showed a characteristic pigmentary retinopathy with a mean age at diagnosis of 47.9 years (17 to 92) and VA of 0.14 logMAR (- 0.12 to 1.24). Age at diagnosis of retinopathy was linearly correlated with age at diagnosis of hearing loss or diabetes (p < .001). Patients with retinopathy were more likely to have hearing loss (83.6% vs. 56.5%, p = .03) or diabetes (56.7% vs. 17.4%, p = .001) than those without retinopathy. Those with both hearing loss and diabetes had an earlier onset of retinopathy than those without (46.4 vs. 60.4 years, p = .01). Patients without both hearing loss and diabetes were 5.3-fold less likely to develop a retinopathy.

CONCLUSIONS

Patients with m.3243A>G variant pigmentary retinopathy maintain highly functional VA until around the fifth decade of life, after which significant visual decline ensues. Patients without hearing loss and diabetes have a lower likelihood of exhibiting a retinopathy, which tends to appear about one decade after hearing loss and diabetes are diagnosed.

Molecular mechanisms of β-cell dysfunction and death in monogenic forms of diabetes

Monogenetic forms of diabetes represent 1%-5% of all diabetes cases and are caused by mutations in a single gene. These mutations, that affect genes involved in pancreatic β-cell development, function and survival, or insulin regulation, may be dominant or recessive, inherited or de novo. Most patients with monogenic diabetes are very commonly misdiagnosed as having type 1 or type 2 diabetes. The severity of their symptoms depends on the nature of the mutation, the function of the affected gene and, in some cases, the influence of additional genetic or environmental factors that modulate severity and penetrance. In some patients, diabetes is accompanied by other syndromic features such as deafness, blindness, microcephaly, liver and intestinal defects, among others. The age of diabetes onset may also vary from neonatal until early adulthood manifestations. Since the different mutations result in diverse clinical presentations, patients usually need different treatments that range from just diet and exercise, to the requirement of exogenous insulin or other hypoglycemic drugs, e.g., sulfonylureas or glucagon-like peptide 1 analogs to control their glycemia. As a consequence, awareness and correct diagnosis are crucial for the proper management and treatment of monogenic diabetes patients. In this chapter, we describe mutations causing different monogenic forms of diabetes associated with inadequate pancreas development or impaired β-cell function and survival, and discuss the molecular mechanisms involved in β-cell demise.

A single-arm, open-label, intervention study to investigate the improvement of glucose tolerance after administration of the 5-aminolevulinic acid (5-ALA) in the patients with mitochondrial diabetes mellitus

BACKGROUND

Mitochondrial diabetes mellitus (MDM) is characterized by maternal inheritance, progressive neurosensory deafness, insulin secretory disorder, and progressive microvascular complications. Mitochondria are critical organelles that provide energy in the form of adenosine triphosphate (ATP). An impairment of ATP production in pancreatic β cells is regarded as the main cause of the insulin secretory disorder in patients with MDM, and these patients require insulin replacement therapy early after the diagnosis. The amino acid 5-aminolevulinic acid (5-ALA), a precursor of heme metabolites, is a non-proteinogenic δ amino acid synthesized in mitochondria. An addition of ferrous iron to 5-ALA enhances heme biosynthesis and increases ATP production through an upregulation of the respiratory complex. Several studies have reported that the administration of 5-ALA and ferrous iron to existing treatment improved the glycemic control in both patients with prediabetes and those with type 2 diabetes mellitus. The additional administration of 5-ALA and ferrous iron to MDM patients on insulin therapy may improve their insulin secretory capacity and glycemic control by improving their mitochondrial function. The findings of this study are expected to provide new treatment options for MDM and improve the patients' glycemic control and prognosis.

METHODS/DESIGN

This study is a single-arm, open-label pilot intervention study using clinical endpoints to investigate the effects of treatment with 5-ALA plus sodium ferrous citrate (SFC) to patients with MDM on their glucose tolerance. A total of 5 patients with MDM will be administered 5-ALA/SFC (200 mg/d) for 24 weeks. We will perform a 75-g oral glucose tolerance test before and at 24 weeks after the start of this 5-ALA/SFC treatment to evaluate glucose-dependent insulin responses.

DISCUSSION

To the best of our knowledge, this study will be the first assessment of the effects of 5-ALA/SFC in patients with MDM. This study will obtain an evidence regarding the effectiveness and safety of 5-ALA/SFC for patients with MDM.

TRIAL REGISTRATION

This study was registered with the University Hospital Medical Information Network (UMIN000040581) on July 1, 2020 and with the Japan Registry of Clinical Trials (jRCTs071200025) on August 3, 2020.

Mitochondrial DNA A3243G variant-associated retinopathy: Current perspectives and clinical implications

Cellular function and survival are critically dependent on the proper functionality of the mitochondrion. Neurodegenerative cellular processes including cellular adenosine triphosphate production, intermediary metabolism control, and apoptosis regulation are all mitochondrially mediated. The A to G transition at position 3243 in the mitochondrial MTTL1 gene that encodes for the leucine transfer RNA (m.3243A>G) causes a variety of diseases, including maternally inherited loss of hearing and diabetes syndrome (MIDD), mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes syndrome (MELAS). Ophthalmological findings-including posterior sub-capsular cataract, ptosis, external ophthalmoplegia, and pigmentary retinopathy- have all been associated with the m.3243A>G variant. Pigmentary retinopathy is, however, the most common ocular finding, occurring in 38% to 86% of cases. To date, little is known about the pathogenesis, natural history, and heteroplasmic and phenotypic correlations of m.3243A>G-associated pigmentary retinopathy. We summarize the current understanding of mitochondrial genetics and pathogenesis of some associated diseases. We then review the pathophysiology, histology, clinical features, treatment, and important ocular and systemic phenotypic manifestations of m.3243A>G variant associated retinopathy. Mitochondrial diseases require a multidisciplinary team approach to ensure effective treatment, regular follow-up, and accurate genetic counseling.

Multimodal imaging analysis of macular dystrophy in patient with maternally inherited diabetes and deafness (MIDD) with m.3243A>G mutation

Purpose: Maternally inherited diabetes and deafness (MIDD) is caused by a heteroplasmic m.3243A>G mutation in the mitochondrial DNA. The main ocular feature in MIDD is macular dystrophy. The purpose of this study was to identify the phenotypical characteristics of a patient with MIDD by multimodal high-resolution imaging analyses.Methods: A detailed history and ophthalmic examination were performed on a 39-year-old patient with MIDD. Multi-modal imaging included fundus photography, fundus autofluorescence imaging, fluorescein angiography, spectral-domain optical coherence tomography, OCT-angiography, and adaptive optics imaging. The PCR-invader and whole exome sequencing (WES) methods were performed on the DNA of the patient.Results: A 39-year-old woman with sensorineural hearing loss, diabetes mellitus presented with atrophic perifoveal changes and MIDD was suspected. The PCR-invader and WES methods showed that the patient had a m.3243A>G mutation in the mitochondrial DNA with 29% and 16.7% of the heteroplasmy in the peripheral blood, respectively. Morphological analyses revealed that the areas of photoreceptor degeneration and chorioretinal atrophy were present mainly in the perifoveal region. Multifocal ERGs showed that the perifoveal responses were reduced. Goldmann visual field was significant for a cecocentral scotoma in the right eye and an enlarged blind spot in the left eye. The central isopter was constricted bilaterally. The results of high-resolution retinal imaging by AO revealed that the densities of the cone photoreceptor were significantly reduced in the fovea where no obvious atrophy of the RPE and choroid was observed.Conclusions: Our findings indicate that WES analysis can be used to detect the m.3243A>G mutation in the mtDNA. The results of multimodal imaging analyses indicated that the primary dysfunction of the photoreceptors in the fovea might precede the dysfunction of the RPE in patient with MIDD.

Good Glycemic Outcomes Following Bariatric Surgery Among Patients With Type 2 Diabetes, Obesity, and Low-Titer GAD Antibodies

OBJECTIVE

To evaluate diabetes remission after bariatric surgery by presence of GAD antibody among those with obesity and type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

Screening GAD was performed in 221 patients with T2D and obesity referred for bariatric surgery. Nine of 16 patients with GAD and 112 of 205 without GAD proceeded with surgery. Diabetes remission and weight loss were compared by GAD presence.

RESULTS

The group with GAD had levels 16-91 IU/mL. Those with and without GAD were similar with regard to age, BMI, diabetes duration, proportion treated with insulin, HbA_1c, and C-peptide (1,354 ± 548 vs. 1,358 ± 487 pmol/L). At 1 and 5 years postoperatively, the two groups achieved similar BMI reduction and diabetes remission (67% vs. 73%, P = 0.71, and 56% vs. 57%, P = 1.0).

CONCLUSIONS

Low-titer GAD in patients with T2D and retained C-peptide should not be a deterrent for bariatric surgery when the principal aim is diabetes remission.

Neuro-ophthalmic manifestations of mitochondrial disorders and their management

The visual system has high metabolic requirements and is therefore particularly vulnerable to mitochondrial dysfunction. The most commonly affected tissues include the extraocular muscles, photoreceptors, retinal pigment epithelium, optic nerve and visual cortex. Hence, the most common manifestations of mitochondrial disorders are progressive external ophthalmoplegia, macular pattern dystrophy, pigmentary retinopathy, optic neuropathy and retrochiasmal visual field loss. With the exception of Leber hereditary optic neuropathy and stroke-like episodes seen in mitochondrial encephalopathy, lactic acidosis and stroke-like episodes, the majority of neuro-ophthalmic manifestations have an insidious onset. As such, some patients may not recognize subtle progressive visual symptoms. When mitochondrial disorders are highly suspected, meticulous examination performed by an ophthalmologist with targeted ancillary testing can help confirm the diagnosis. Similarly, neuro-ophthalmic symptoms and signs may be the first indication of mitochondrial disease and should prompt systemic investigations for potentially life-threatening associations, such as cardiac conduction defects. Finally, the ophthalmologist can offer symptomatic treatments for some of the most disabling manifestations of these disorders.

Outer retinal tubulation and inner retinal pseudocysts in a patient with maternally inherited diabetes and deafness evaluated with optical coherence tomography angiogram

A 47-year-old lady (index case) with diabetes and deafness showed multiple oval circumferential areas of perifoveal atrophy in both eyes. Autofluorescence revealed areas of hypoautofluorescence. Optical coherence tomography (OCT) showed depression of inner retinal surface, inner retinal hyporeflective spaces (pseudocysts), disorganization/thinning of outer retina, outer retinal tubulation, loss of external limiting membrane, ellipsoid and interdigitation zone, and thinning of the retinal pigment epithelium and choriocapillaris. The patient was evaluated using OCT angiogram. Retinal lesions of her mother (68-year-old) were very obvious on autofluorescence imaging. The result of A3243G mutation in MTTL1 gene was positive in the index case confirming the diagnosis of maternally inherited diabetes and deafness (MIDD).

Evidence of complement dysregulation in outer retina of Stargardt disease donor eyes

Stargardt macular degeneration (STGD) is a central blinding disease caused by loss of or dysfunctional ABCA4 transporter in both photoreceptors and retinal pigment epithelial (RPE) cells. Toxic bisretinoid-lipofuscin buildup in the RPE cells is a pathological hallmark of STGD patients and its mouse model, the Abca4^-/-. These vitamin A-derived fluorophores have been shown to induce oxidative stress, stimulate complement activity, and cause chronic inflammation of the RPE. In vivo modulation of complement regulatory pathway in the STGD mouse model has partially rescued the STGD phenotype suggesting that complement attack on the RPE is an important etiologic factor in disease pathogenesis. While bisretinoid-dependent complement activation was further evidenced in cultured RPE cells, this pathway has never been investigated directly in the context of RPE from STGD donor eyes. In the current study, we evaluate the complement reactivity in postmortem donor eyes of clinically diagnosed STGD patients. All three STGD donor eyes RPE displayed strong immunoreactivity for an antibody specific to 4-Hydroxynonenal, a lipid peroxidation byproduct. Also, unlike the control eyes, all three STGD donor eyes showed significantly increased membrane attack complex deposition on the RPE cells. In STGD eyes, increased MAC accumulation was mirrored by elevated C3 fragments internalized by the RPE and inversely correlated with the levels of complement factor H, a major complement regulatory protein. Here, we report the first direct evidence of RPE complement dysregulation as a causative factor in developing Stargardt phenotype.

Chronic kidney disease caused by maternally inherited diabetes and deafness: a case report

Maternally inherited diabetes and deafness (MIDD) is a mitochondrial genetic disorder with variable clinical presentations, which can delay its diagnosis. Herein, we report the case of a 57-year-old Japanese man with MIDD who developed chronic kidney disease. He developed proteinuria long before his diabetes and deafness; at the age of 36 years, a renal biopsy showed minor glomerular abnormality and electron microscopy showed mild mitochondrial degeneration in the distal tubular epithelial cells. Twenty years later, a second renal biopsy showed nephrosclerosis with interstitial fibrosis and arteriolar hyaline thickening, despite the absence of hypertension and relatively good glycemic control. Granular swollen epithelial cells were found in the medullary collecting duct epithelium. Electron microscopy showed accumulating mitochondria in podocytes and tubular cells, leading to the diagnosis of MIDD. A muscle biopsy also showed ragged-red fibers, despite the absence of muscle weakness. Mitochondrial DNA analysis revealed an m.3243A > G mutation, and taurine supplementation was initiated. Our findings suggest that mitochondrial dysfunction is mainly associated with progressive renal damage.

Intravitreal bevacizumab in cystoid macular edema associated to maternally inherited diabetes and deafness's macular dystrophy

INTRODUCTION

Maternally inherited diabetes and deafness (MIDD) is a rare and infradiagnosed cause of diabetes which can, in a high number of cases, associate a macular dystrophy.

CASE PRESENTATION

We report the case of a 49- year-old man affected of this syndrome, with proven m3243G>A mitochondrial mutation, who developed macular cysts 20 years after the initial presentation of his macular dystrophy. The fluorescein angiography showed no leakage, ruling out a diabetic macular edema. A treatment with intravitreal bevacizumab led to cystic changes resolution and visual acuity recovery.

CONCLUSION

Intravitreal bevacizumab can be successfully employed for this complication of MIDD's macular dystrophy.

Sleep-Disordered Breathing in Adult Patients With Mitochondrial Diseases: A Cohort Study

OBJECTIVE

To describe the prevalence and characteristics of sleep-disordered breathing (SDB) in a large cohort of patients with genetically confirmed mitochondrial diseases.

METHODS

This is a prospective observational study performed at the Neurophysiopatology Unit of Fondazione Policlinico Universitario A. Gemelli IRCCS. All participants had a defined mitochondrial disease and were investigated by full-night polysomnography.

RESULTS

One hundred three consecutive patients were enrolled. SDB was demonstrated in 49 patients (47.6%). Regarding phenotypes, we found differences in distribution between the groups: patients affected by progressive external ophthalmoplegia with single or multiple mtDNA deletions frequently had obstructive apneas (50% and 43.8%) or REM-related hypoventilation when associated with m.3243A>G mutations (75%). Furthermore, a high percentage of participants with maternally inherited diabetes and deafness and myoclonic epilepsy with ragged-red fibers syndromes were characterized by obstructive sleep apnea and REM-related hypoventilation, respectively. In contrast to what has been described in previous studies, central sleep apnea was rarely reported in our cohort.

CONCLUSIONS

SDB has a higher prevalence in mitochondrial diseases compared to general population-based data. Overall, these results suggest that patients characterized by a specific phenotype-genotype combination are most at risk of developing a specific subgroup of SDB. The early identification of this disorder is crucial in the management of these fragile patients.

Age-related macular degeneration masqueraders: From the obvious to the obscure

Age-related macular degeneration (AMD) is one of the leading causes of blindness worldwide with increasing prevalence owing to increased life expectancy. Intravitreal injections of antivascular endothelial growth factor agents are commonly used in exudative AMD and oral antioxidant medication for nonexudative AMD; however, many disorders mimic exudative and nonexudative AMD, and misdiagnosis can seriously affect the management of these patients. We summarize the demographics and clinical and imaging characteristics of each of the conditions that masquerade as AMD. As some of the conditions have features of AMD, a short update on the classical features of AMD is also included.

The first concurrent detection of mitochondrial DNA m.3243A>G mutation, deletion, and depletion in a family with mitochondrial diabetes

BACKGROUND

Mitochondrial diabetes (MD) is a rare monogenic form of diabetes and divided into type l and type 2. It is characterized by a strong familial clustering of diabetes with the presence of maternal transmission in conjunction with bilateral hearing impairment in most of the carriers. The most common form of MD is associated with the m.3243A>G mutation in the mitochondrial MT-TL1, but there are also association with a range of other point mutations, deletion, and depletion in mtDNA.

METHODS

The mitochondrial genome anomalies were investigated in a family with clinical features of MD, which includes a proband presenting severe MD conditions including cardiomyopathy, retinopathy, and psychomotor retardation.

RESULTS

By investigating the patient's blood leukocytes and skeletal muscle, we identified the m.3243A>G mutation in heteroplasmic state. This mutation was absent in the rest of the family members. In addition, our analysis revealed in the proband a large mtDNA heteroplasmic deletion (~1 kb) and a reduction in mtDNA copy number.

CONCLUSION

Our study points out, for the first time, a severe phenotypic expression of the m.3243A>G point mutation in association with mtDNA deletion and depletion in MD.

Clinical phenotype of mitochondrial diabetes due to rare mitochondrial DNA mutations

OBJECTIVE

While the most frequent mutation responsible for mitochondrial diabetes is the point mutation m.3243 A>G of mitochondrial DNA (mtDNA), few data are available about the role of rare mtDNA mutations in the pathophysiology of diabetes. The main objective of our study was to describe the phenotypic characteristics of patients suffering from diabetes linked to rare mtDNA mutations.

RESEARCH DESIGN AND METHODS

We performed a post-hoc analysis of a prospective multicenter cohort of 743 patients with mitochondrial disorder (previously published by the French Network of Mitochondrial Diseases), associated to a literature review of the PubMed database from 1992 to May 2016. We extracted all reported patients with diabetes and identified rare mtDNA mutations and described their clinical and metabolic phenotypes.

RESULTS

The 50 identified patients (10 from the princeps study; 40 from the review of the literature) showed a heterogeneous metabolic phenotype in terms of age, symptoms prior to diagnosis, treatments, and associated clinical and biological signs. However, neurological symptoms were more frequent in case of rare mtDNA mutations compared to the classical m.3243 A>G mutation (P=0.024). In contrast, deafness (65% vs. 95%, P=3.7E-5), macular pattern dystrophy (20% vs. 86%, P=1.6E-10) and nephropathy (8% vs. 28%, P=0.018) were significantly less frequent than in case of the classical m.3243 A>G mutation.

CONCLUSION

Although no specific metabolic phenotype could be identified suggesting or eliminating implication of rare mtDNA mutations in diabetes, clinical phenotypes featured more frequent neurological signs.

Incidence and associates of diabetic ketoacidosis in a community-based cohort: the Fremantle Diabetes Study Phase II

OBJECTIVE

To assess the incidence and associates of diabetic ketoacidosis (DKA) in a representative community-based cohort.

METHODS

All hospitalizations of 1724 participants in the Fremantle Diabetes Study Phase II for/with DKA (plasma glucose >13.8 mmol/L, urinary/serum ketones, serum bicarbonate <18 mmol/L and/or arterial/venous pH <7.30) were identified between study entry from 2008 to 2011 and end-2013. Details of each episode were categorized by chart review as confirmed/probable DKA, possible DKA or not DKA. Incidence rates by diabetes type were calculated. Cox proportional hazards modeling determined predictors of first episode, and negative binomial regression identified predictors of frequency.

RESULTS

There were 53 coded DKA episodes (41 first episodes, 12 recurrences), of which 19 (35.8%) were incorrectly coded, 9 (17.0%) had possible DKA and 25 (47.2%) had confirmed/probable DKA. Of this latter group, 44% had type 1 diabetes, 32% had type 2 diabetes, 12% had latent autoimmune diabetes of adults (LADA) and 12% had secondary diabetes. The overall incidence of confirmed/probable DKA (95% CI) was 35.6 (23.0 to 52.6)/10 000 person-years (178.6 (85.7 to 328.5)/10 000 person-years for type 1 diabetes, 13.3 (5.7 to 26.1)/10 000 person-years for type 2 diabetes, 121.5 (33.1 to 311.0)/10 000 person-years for LADA and 446.5 (92.1 to 1304.9)/10 000 person-years for secondary diabetes). Baseline ln(fasting serum C-peptide) (inversely), glycated hemoglobin and secondary diabetes predicted both incident first confirmed/probable DKA episode and the frequency of DKA (p<0.001).

CONCLUSIONS

These data highlight the contribution of poor glycemic control and limited pancreatic beta cell function to incident DKA, and show that people with types of diabetes other than type 1, especially secondary diabetes, are at risk.

Genetic studies of focal segmental glomerulosclerosis: a waste of scientific time?

Many genetic causes of focal segmental glomerulosclerosis (FSGS) have been described. A paradox is that the science in the molecular biology, which generally appears of high quality, is not mirrored by a similarly critical analysis of the renal pathology. FSGS has been applied to such a wide range of conditions that it can reasonably be said to have no useful meaning. Attempts to refine the term have been largely ignored. Study of 252 papers on genetic causes of FSGS found various clinical features. Many papers took the reported diagnosis without question. Few papers reported a pathological review, almost half reported FSGS and up to six other conditions caused by any particular gene, some reported FSGS with recognisable glomerular disorders, over 80% did not apply the Columbia classification, and in nearly all with photomicrographs, the images were not useful for refinement of FSGS. Some workers commented on a lack of genotype-phenotype correlation. One reason is a disregard of the principle that scientific investigation requires an unambiguous definition of the condition studied, to allow others to replicate or refute the findings. Genetic studies of FSGS should use a similarly rigorous approach to renal pathology to that used in molecular biology.