Multidisciplinary approach to inherited causes of dual sensory impairment

PURPOSE

This article presents a review of the main causes of inherited dual sensory impairment (DSI) with an emphasis on the multidisciplinary approach.

METHODS

A narrative review of English literature published before January 2023 was conducted using PubMed, Medline, and Scopus databases. The different causes of inherited DSI are discussed from a multidisciplinary perspective.

RESULTS

There are a wide range of dual sensory impairment (DSI), commonly referred to as blindness and deafness. While Usher syndrome is the most frequent genetic cause, other genetic syndromes such as Alport syndrome or Stickler syndrome can also lead to DSI. Various retinal phenotypes, including pigmentary retinopathy as seen in Usher syndrome, vitreoretinopathy as in Stickler syndrome, and macular dystrophy as in Alport syndrome, along with type of hearing loss (sensorineural or conductive) and additional systemic symptoms can aid in diagnostic suspicion. A thorough ophthalmologic and otorhinolaryngologic examination can help guide diagnosis, which can then be confirmed with genetic studies, crucial for determining prognosis. Effective hearing rehabilitation measures, such as hearing implants, and visual rehabilitation measures, such as low vision optical devices, are crucial for maintaining social interaction and proper development in these patients.

CONCLUSIONS

While Usher syndrome is the primary cause of inherited dual sensory impairment (DSI), other genetic syndromes can also lead to this condition. A proper diagnostic approach based on retinal phenotypes and types of hearing loss can aid in ruling out alternative causes. Multidisciplinary approaches can assist in reaching a definitive diagnosis, which has significant prognostic implications.

NOVEL RETINAL IMAGING ABNORMALITIES IN ALPORT SYNDROME

PURPOSE

The purpose of this study was to report a novel observation during retinal screening of a child with Alport syndrome.

METHODS

This was a review of case record and imaging files.

RESULTS

Clinical examination of the retina and standard color fundus photography revealed no abnormality. However, distinct and identical wrinkling of the temporal macula (fingerprint sign) in both eyes was noted on Optos pseudocolor images of the retina. On optical coherence tomography, there were corresponding "saw-tooth" corrugations in the middle layers of the retina. En face images further highlighted the characteristic nature of this unusual observation.

CONCLUSION

Fingerprint sign in the retina, a heretofore undescribed feature, is reported in a child with biopsy confirmed Alport syndrome.

Whole exome sequencing identifies monogenic forms of nephritis in a previously unsolved cohort of children with steroid-resistant nephrotic syndrome and hematuria

BACKGROUND

Alport syndrome (AS), atypical hemolytic-uremic syndrome (aHUS), and fibronectin-glomerulopathy (FG) are rare forms of glomerular diseases that manifest in a combination of proteinuria, hematuria, and hypertension, referred to as nephritic syndrome. Due to phenotypic overlays, steroid-resistant nephrotic syndrome (SRNS) and nephritic syndrome have been difficult to discern diagnostically. SRNS is more common than nephritic syndrome and is the second leading cause of childhood-onset CKD. Fourteen monogenic causes of AS, aHUS, and FG and 60 monogenic causes of SRNS have been identified. As whole exome sequencing (WES) allows for unequivocal molecular genetic diagnostics, we hypothesize to be able to identify causative mutations in genes known to cause nephritic syndrome in patient cohorts with a clinical diagnosis of SRNS.

METHODS

We identified patients with hematuria and steroid-resistant proteinuria in an international patient cohort that we had submitted to WES and who were unsolved for known monogenic causes of SRNS. These 70 patients from 65 individual families were subsequently analyzed for causative mutations in 14 AS, aHUS, or FG causing genes. WES data were compared to a control cohort of 76 patients from 75 families that were diagnosed with nephronophthisis-related ciliopathies (NPHP-RC) and to a control cohort of 83 individuals from 75 families with SRNS, but without hematuria.

RESULTS

We detected likely pathogenic genetic variants in 3 of 65 families (4.6%) in 2 of the 14 genes analyzed.

CONCLUSIONS

We confirmed that in cohorts of childhood-onset SRNS, patients with nephritic syndrome can be discerned by WES. The findings highlight the importance of clinical genetic testing for therapeutic and preventative measures in patients with proteinuria. A higher resolution version of the Graphical abstract is available as Supplementary information.

Cooccurrence of Alport syndrome and poststreptococcal acute glomerulonephritis with improvement after steroid administration

It is clinically possible for patients with Alport syndrome (AS) to suffer from poststreptococcal acute glomerulonephritis (PSAGN). However, there is only one report of such a patient, and he had end-stage kidney disease. Here, we describe an 8-year-old male with X-linked AS and chronic kidney disease (CKD) stage G2. He presented with diffuse edema, gross hematuria, proteinuria, and body weight gain after streptococcal pharyngitis. Blood examination showed kidney dysfunction, hypocomplementemia, and increased anti-streptolysin-O levels. His kidney function did not improve with symptomatic treatment. Therefore, we started steroid administration on the 12th day of hospitalization. Then, his kidney function improved before he was discharged. We confirmed that his complement function had recovered at a later date. Pathological evaluation showed findings of AS and PSAGN, including cellular crescents in 3/30 glomeruli on light microscopy. In addition, electron dense deposits (EDDs) were seen in not only the visceral subepithelium but also the glomerular basement intramembrane and subendothelium, some of which were hump-like. Although AS and CKD are indicated to have a poor prognosis in PSAGN, our patient recovered after administration of steroids. Our case suggests that we can consider the administration of steroids, including pulse therapy for PSAGN, when patients have, for example, crescents on pathology, severe renal dysfunction, nephrotic proteinuria, or AS with CKD, as in our case. Kidney pathology suggested that a typical hump is not seen in patients with cooccurring AS and PSAGN. After the patient's kidney function recovered, we continued to follow him.

Extra-axial haemorrhage in a patient with Alport syndrome after epidural anaesthesia

Extra-axial haemorrhage following epidural anaesthesia is extremely rare. We present the case of an 18-year-old G1P0 woman with Alport syndrome who had a ventouse delivery for failure to progress that was complicated by a postpartum tonic-clonic seizure. Clinically, and confirmed radiologically, the patient was found to have experienced an extra-axial haemorrhage (extradural and subdural haemorrhage) secondary to a cerebrospinal fluid leak caused by a dural puncture during epidural anaesthesia. Differentiating between postdural puncture headache, subdural haemorrhage and extradural haemorrhage can be extremely challenging, but it is important to consider these rare conditions when evaluating patients presenting with postpartum headache and seizure.

HMGB-1 and TGFβ-1 highlight immuno-inflammatory and fibrotic processes before proteinuria onset in pediatric patients with Alport syndrome

INTRODUCTION

Alport syndrome (ALP) is a rare genetic condition characterized by progressive involvement of the basal membranes and renal dysfunction. The purpose of the study was to evaluate urinary (u) and serum (s) levels of tumor growth factor (TGF)-beta(β) and high mobility group box (HMGB)-1 in ALP patients with normal renal function, albuminuria and proteinuria.

METHODS

A prospective, single-center study was performed with a follow-up period of 12 months, enrolling 11 pediatric ALP patients and 10 healthy subjects (HS). Normal values of serum creatinine, albuminuria and proteinuria, as well as unaltered estimated glomerular filtration rate (eGFR) were required at enrollment.

RESULTS

ALP patients had significantly higher levels of serum and urinary HMGB1 compared to HS. The same trend was observed for TGF-β1, with higher values in ALP patients than in HS. HMGB1 and TGF-β1 correlated with each other and with markers of renal function and damage. Urinary biomarkers did not correlate with eGFR, whereas sHMGB1 and sTGF-β1 were negatively related to filtration rate (r: - 0.66; p = 0.02, r: - 0.96; p < 0.0001, respectively). Using proteinuria as a dependent variable in a multiple regression model, only the association with sTGF-β1 (β = 0.91, p < 0.0001) remained significant.

CONCLUSIONS

High levels of HMGB1 and TGF-β1 characterized ALP patients with normal renal function, highlighting the subclinical pro-fibrotic and inflammatory mechanisms triggered before the onset of proteinuria. Further studies are needed to evaluate the role of HMGB1 and TGFβ-1 in ALP patients.

[Fabry disease]

Fabry disease. Fabry disease is an X-linked disorder in which lysosomal alpha-galactosidase A is lacking, leading to enzyme-substrate accumulation and tissues dysfunction. Acroparesthesia, angiokeratoma, familial nephropathy or hypertrophic cardiomyopathy should suggest Fabry disease. Enzymatic assay allows diagnosis in men but genetic assay is needed for women. Enzyme replacement therapy is available since 2001 and a pharmacologic chaperone since 2016.

Isolated microscopic haematuria of glomerular origin: clinical significance and diagnosis in the 21st century

Isolated microscopic, or non-visible, haematuria of glomerular origin was previously regarded a benign finding, but it is now known that, even in the absence of proteinuria, hypertension or renal impairment at presentation, haematuria is associated with increased risk of kidney failure in the long term. The most common causes of isolated microscopic haematuria among children and young adults are IgA nephropathy, Alport syndrome (AS), and thin basement membrane nephropathy (TBMN). AS, which is usually inherited as an X-linked or autosomal recessive trait, and TBMN, which is usually autosomal dominant, are caused by mutations in the genes encoding type-IV collagen, an abundant component of the glomerular basement membrane. A detailed family history with screening of at-risk relatives is important, allowing prompt diagnosis of affected relatives and helping determine the mode of transmission. As costs fall and availability increases, genetic testing is increasingly being used in clinical practice to provide diagnostic and predictive information for patients and their families.

[Comparison of phenotypic features between patients with X-linked and autosomal recessive Alport syndrome]

OBJECTIVE

To further improve the recognition of Alport syndrome.

METHODS

The patients with COL4A3, COL4A4 or COL4A5 mutations, admitted to Department of Pediatric, Peking University First Hospital from 2005 to 2009, were retrospectively studied. Their clinical and ultrastructural characteristics were compared between the male patients with X-linked dominant inheritance Alport syndrome (XLAS) and the patients with autosomal recessive inheritance Alport syndrome (ARAS).

RESULTS

There were 54 male patients with XLAS and 14 patients with ARAS. Compared with the male patients with XLAS, episodic gross hematuria was prominent (P<0.001) in patients with ARAS. Family history was also different between the two groups (P=0.016). However, there was no significant difference in the age of identification of symptoms, initial manifestations, levels of proteinuria, extrarenal signs and ultra-structural glomerular basement membrane changes between the two groups.

CONCLUSION

There are some features that distinguish between the patients with XLAS and the patients with ARAS.

[Autosomal dominant macrothrombocytopenia with leukocyte inclusion bodies and MYH9 disorders]

May-Hegglin anomaly (MHA) is the prototype of autosomal dominant macrothrombocytopenia with leukocyte inclusion bodies/MYH9 disorders that result from mutations in MYH9, the gene for nonmuscle myosin heavy chain-IIA (NMMHC-IIA). Others include Sebastian, Fechtner, and Epstein syndromes. A clear phenotype-genotype relationship has not been found; however, patients with an MYH9 head domain mutation tend to develop Alport manifestations more frequently than those with a rod domain mutation. Patients initially diagnosed with MHA and/or Sebastian syndrome can subsequently develop nephritis, deafness, and/or cataracts. Thus, the development of Alport manifestations should be monitored by careful follow-up.

Tissue-specific distribution of an alternatively spliced COL4A5 isoform and non-random X chromosome inactivation reflect phenotypic variation in heterozygous X-linked Alport syndrome

A novel type of hereditary transmission of COL4A5 in a Japanese family with X-linked Alport syndrome was detected through analysis of cDNA sequences and an X-chromosome inactivation assay. A female patient with moderately altered renal function, who was diagnosed with Alport syndrome by renal biopsy, and her mother, who was undergoing maintenance haemodialysis, showed similar tissue-specific expression of a truncated isoform of COL4A5, which was generated by alternative splicing without a splice-site mutation. Expression of the truncated isoform occurred in the renal specimen derived from the patient, but not in specimens from controls. Genomic analysis revealed two point mutations (c.4821 + 121, T>C; c.4822-151_150, ins T) in intron 49 of COL4A5 from the patient. The peripheral blood mononuclear cells of the patient and her mother showed non-random lyonization. While the females showed only renal impairment, an affected male in the same family suffered from severe renal insufficiency, visual defect and hearing disturbances. Hence, we suggest that this type of heredity COL4A5 presents with phenotypic variation in female heterozygous X-linked Alport syndrome patients.

Animal models of renal fibrosis

Most of the present knowledge on pathomechanism of renal fibrosis is based on experimental studies with laboratory animals. Today, a variety of genetic and inducible animal models that mimic primary causes of human disease such as diabetes mellitus, glomerulonephritis, or lupus erythematodes are available. However, only few of these models progress consistently to interstitial fibrosis in the kidney involving interestitial fibrosis, tubular atrophy, and glomerulosclerosis, which are common features of renal fibrogenesis. In this chapter, the mouse models of nephrotoxic serum nephritis, COL4A3-deficiency, and unilateral urethral obstruction, which all result reliably into renal fibrosis, are described.

Fechtner syndrome: physiologic analysis of macrothrombocytopenia

Fechtner syndrome is a rare autosomal dominant disorder consisting of macrothrombocytopenia and leukocyte inclusions, associated with Alport's syndrome (hereditary nephropathy, sensorineural hearing loss, and ocular anomalies). We describe a 71-year-old Caucasian male with a history of hearing loss and asymptomatic macrothrombocytopenia incidentally noted in 1985. Several challenges to hemostasis were uneventful, including total hip arthroplasty. He subsequently developed progressive renal failure, with 'nil lesions' by light and electron microscopy, which was responsive to corticosteroid therapy. Eight family members are affected variably by either thrombocytopenia or renal failure. Laboratory testing gave the following results: hemoglobin, 10.2 g/dl; leukocytes, 5.0 x 109/l; platelets, 64 x 109/l (mean platelet volume, 13.3 fl; normal platelet volume, 7.6-10.8 fl). Peripheral blood smear revealed thrombocytopenia and leukocytes with inclusions. Electron microscopy of the buffy coat confirmed Fechtner inclusions within the patient's leukocytes. Whole mount and thin section electron microscopy revealed a population of large, although not giant, platelets. Despite thrombocytopenia, platelet aggregation was normal. Flow cytometry of dilute platelets revealed normal glycoprotein alphaII beta beta3 activation and alpha-granule p-selectin secretory response to 10 nmol/l human alpha-thrombin. Dense granule adenosine triphosphate secretory response to thrombin was likewise normal. This case illustrates that 'giant' platelets are not universally present in Fechtner syndrome cases, although the platelets are enlarged. Finally, renal pathology other than Alport's nephropathy may be associated with this syndrome.

Glomerulonephritis in childhood

Safer renal biopsy techniques have led to increased recognition of the various forms of glomerulonephritis in the pediatric population. Our understanding of their natural history and progression has improved, and we now know that there is significant morbidity associated with diseases such as IgA nephropathy and membranoproliferative glomerulonephritis. Knowledge of the pathophysiology of progressive renal disease has also expanded, but specific treatment modalities, especially for children, are lacking and continue to be areas for future clinical research. This article reviews four types of glomerulonephritis that occur in childhood: acute poststreptococcal glomerulonephritis, IgA nephropathy, Alport's syndrome, and membranoproliferative glomerulonephritis. The clinical and pathologic features of each are reviewed, and the current literature covering new developments in their prognosis, genetics, or therapies are summarized.

Epstein's syndrome. Implications for oral surgery

Epstein's syndrome is a rare inherited disorder that appears principally as nephritis and deafness with thrombocytopathic thrombocytopenia producing a bleeding tendency. Management of the disorder for oral surgical procedures is discussed and highlighted by a case report.

Absence of Goodpasture's antigen in male patients with familial nephritis

The presence of Goodpasture's (GP) antigen in the glomerular basement membrane (GBM) of the kidney was evaluated by indirect immunofluorescence in nine patients with familial nephritis from five kindreds. The GP antigen was not detected in seven males but was present in an affected sister and mother, an unaffected brother, and 13 normal controls. The specificity of this finding in affected males is supported by the persistence of other GBM antigens identified by monoclonal antibodies. The lack of GP antigen in affected males and its persistence in related females with the disease suggests a possible X-linked dominant mode of inheritance. We propose that the absence of GP antigen leads to severe disease in the male, whereas its presence in related females is associated with mild disease.

Early pathologic features of hereditary nephritis: a clinicopathologic correlation

The histologic, immunofluoresence and electron microscopic features of renal biopsies from twelve patients having hereditary nephritis were examined and correlated with the clinical data. In ten patients with normal renal function, light microscopy showed similar but nonspecific glomerular abnormalities consisting of mild focal and segmental hypercellularity and thickening of capillary walls. Biopsies from two patients with azotemia had diffuse lesions of the glomeruli and associated interstitial fibrosis. There were no characteristic findings on immunofluorescence. Electron microscopy revealed alterations in thickness and density of the glomerular capillary basal lamina in all patients. However, lamellation of the basement membrane and the presence of electron dense granules were present only in the two patients with renal functional impairment. These findings support the view that hereditary nephritis is a form of glomerular disease in which ultrastructural changes in the basal lamina of glomerula capillaries are the earliest and most consistent lesions. However, the morphologic spectrum of these ultrastructural abnormalities is broader than previously recognized.

Complement deficiency and nephritis. A report of a family

A family is described in which three children had homozygous deficiency of C3 and in which both parents and two other children were heterozygous for the C3 null gene. One child with heterozygous C3 deficiency was found to have membranoproliferative glomerulonephritis; proteinuria and/or microscopical haematuria was present in all three homozygous C3-deficient children. All children with homozygous or heterozygous C3 deficiency were, to a varying degree, susceptible to infection. The only child of the family with normal complement had no increased risk of infection and no renal disease. This family study provides further support for the proposal that C3 deficiency predisposes to nephritis.

[Asymptomatic nephritis in relatives living with children with acute poststreptococcal glomerulonephritis]

We studied a group of 114 persons living together with children admitted in the hospital because of poststreptococcal glomerulonephritis; minute count of the urinary sediment, antistreptolysin 0 and throat culture were done. An increased was found in the urinary excretion of erythrocytes in 31% of the population studied; 71% showed a rise of serum antistreptolysin 0 and 9% showed beta hemolytic streptococci in their throat culture. It is important to search for these asymptomatic patients among relatives and follow their course; there is a possibility that some will developed chronic nephritis. It is also important to erradicate the streptococcal infection.

[Deafness in the Muckle-Wells syndrome]

Typical of the syndrome described by Muckle and Wells is a combination of progressive perceptive deafness appearing at various ages in a family, but usually at the same age in the same family, arthralgia, urticarious eruption and renal amyloidosis. The existence of incomplete forms, either without deafness or without renal amyloidosis should be known. This perceptive deafness is very probably due to lesion of the internal ear but the histological characteristics do not seem to be very clear at the present time. Finally, as certain of our observations show, in a few cases, conduction may be impaired, either in isolation, or associated with impairment of perception. Only an analysis of a large number of cases will enable the audiological characteristics of this curious syndrome to be defined.

Anterior lenticonus and Alport's syndrome

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