Prevalence, characteristics, and costs of diagnosed homocystinuria, elevated homocysteine, and phenylketonuria in the United States: a retrospective claims-based comparison

Conquering homocystinuria with engineered probiotics

Pyridoxine-unresponsive homocystinuria has lifelong implications for health. In this issue, Perreault and colleagues present evidence that orally delivered engineered probiotic Escherichia Coli Nissle SYNB1353 is a promising candidate in reducing homocysteine, with successful trials in mice, monkeys, and humans. However, further probiotic optimization and safety assessments are required.

Subtypes of Venous Thromboembolism in Inflammatory Bowel Disease: A Nationwide Assessment

Background

Data detailing the risk of Venous Thromboembolism (VTE) subtypes among individuals with Inflammatory bowel disease (IBD) remain limited.Aims: We looked to assess the odds of VTE subtypes among hospitalized individuals with IBD as compared to those without IBD.

Materials & Methods

Using the Nationwide Inpatient Sample database, we applied a multivariable regression analysis to compare the odds of primary VTE-related hospitalizations among individuals with and without IBD from 2016 to 2020, including deep venous thrombosis (DVT), pulmonary embolism (PE), portal vein thrombosis (PVT), Budd Chiari syndrome (BCS), renal vein thrombosis (RVT), and cerebral venous sinus thrombosis (CVST).

Results

Overall, there were 15,565 primary VTE-related hospitalizations among individuals with IBD, as compared to 1,449,164 among individuals without IBD. Having IBD increased the odds for DVT (aOR = 1.34, 95%CI: 1.25-1.43), PVT (aOR = 3.16, 95%CI: 2.65-3.76), and CVST (aOR=1.45, 95%CI: 1.05-2.00), without significant increase in the odds of a PE, BCS, or RVT. Further, individuals with ulcerative colitis (UC) were at a higher risk for the majority of VTE-subtypes as compared to those with Crohn's disease (CD). Among individuals with a VTE-related hospitalization, the presence of IBD was not associated with increased mortality (aOR = 0.77, 95%CI: 0.40-1.50), but was associated with an increased length of stay (CD - 4.8 days, UC - 5.3 days, without IBD - 4.3 days, p<0.01).

Conclusions

Clinicians should retain a high index of suspicion when evaluating VTE-related symptoms among individuals with IBD, as the presence of IBD confers a higher risk of DVT, PVT and CVST related-hospitalizations, and longer stays as compared to individuals without IBD.

Risk factors for cognitive impairment in middle-aged type 2 diabetic patients: a cross-sectional study

OBJECTIVE

The aim of this study was to investigate risk factors for cognitive impairment (CI) and explore the relationship between obesity and cognition in hospitalised middle-aged patients with type 2 diabetes (T2DM).

METHODS

Subjects were divided into normal cognitive function (NCF) (n=320) and CI (n=204) groups based on the results of the Montreal Cognitive Assessment (MoCA) and Mini-Mental State Examination (MMSE). The risk factors for CI were determined by logistic regression analysis and generalised linear modelling. The associations between obesity parameters (body mass index (BMI) and waist circumference (WC)) and cognitive ability were studied with the use of linear regression analysis, piecewise regression modelling and interaction analysis. The receiver operating characteristic curve analysis was used to examine the diagnostic value of influencing factors for cc RESULTS: The prevalence of CI was 38.9% in hospitalised middle-aged T2DM patients (median age, 58 years). Age, WC, hypoglycaemic episode within past 3 months and cerebrovascular disease (CVD) were identified as independent risk factors for CI, while the independent protective factors were education, diabetic dietary pattern, overweight and obesity. BMI was a protective factor for the MoCA score within a certain range, whereas WC was a risk factor for the MMSE and MoCA scores. The area under the curve for the combination of BMI and WC was 0.754 (p<0.001).

CONCLUSION

Age, education, diabetic dietary pattern, WC, overweight, obesity, hypoglycaemic episode in 3 months and CVD may be potential influencing factors for the occurrence of CI in hospitalised middle-aged population with T2DM. The combination of BMI and WC may represent a good predictor for early screening of CI in this population. Nevertheless, more relevant prospective studies are still needed.

Classical homocystinuria presenting with transient basal ganglia pathology and dystonia

Classical homocystinuria is caused by pathogenic variants in the CBS gene leading to a deficiency of the vitamin B6-dependent enzyme cystathionine beta synthase. The disease is typically associated with high blood homocysteine concentrations. Clinical features include developmental delay/intellectual disability, psychiatric problems, thromboembolism, lens dislocation, and marfanoid habitus. We report on a child with classical homocystinuria presenting with acute episodes of dystonia and symmetrical basal ganglia abnormalities mimicking a mitochondrial disease. After starting treatment with vitamin B6, homocysteine levels rapidly normalized and dystonic episodes did not re-occur. Moreover, brain-imaging findings almost completely disappeared. The case illustrates that homocystinuria should be considered as a treatable differential diagnosis of dystonia.

Phenylalanine hydroxylase deficiency treatment and management: A systematic evidence review of the American College of Medical Genetics and Genomics (ACMG)

PURPOSE

Elevated serum phenylalanine (Phe) levels due to biallelic pathogenic variants in phenylalanine hydroxylase (PAH) may cause neurodevelopmental disorders or birth defects from maternal phenylketonuria. New Phe reduction treatments have been approved in the last decade, but uncertainty on the optimal lifespan goal Phe levels for patients with PAH deficiency remains.

METHODS

We searched Medline and Embase for evidence of treatment concerning PAH deficiency up to September 28, 2021. Risk of bias was evaluated based on study design. Random-effects meta-analyses were performed to compare IQ, gestational outcomes, and offspring outcomes based on Phe ≤ 360 μmol/L vs > 360 μmol/L and reported as odds ratio and 95% CI. Remaining results were narratively synthesized.

RESULTS

A total of 350 studies were included. Risk of bias was moderate. Lower Phe was consistently associated with better outcomes. Achieving Phe ≤ 360 μmol/L before conception substantially lowered the risk of negative effect to offspring in pregnant individuals (odds ratio = 0.07, 95% CI = 0.04-0.14; P < .0001). Adverse events due to pharmacologic treatment were common, but medication reduced Phe levels, enabling dietary liberalization.

CONCLUSIONS

Reduction of Phe levels to ≤360 μmol/L through diet or medication represents effective interventions to treat PAH deficiency.

An orally administered enzyme therapeutic for homocystinuria that suppresses homocysteine by metabolizing methionine in the gastrointestinal tract

Classical homocystinuria (HCU) is a rare inborn error of amino acid metabolism characterized by accumulation of homocysteine, an intermediate product of methionine metabolism, leading to significant systemic toxicities, particularly within the vascular, skeletal, and ocular systems. Most patients require lifelong dietary therapy with severe restriction of natural protein to minimize methionine intake, and many patients still struggle to maintain healthy homocysteine levels. Since eliminating methionine from the diet reduces homocysteine levels, we hypothesized that an enzyme that can degrade methionine within the gastrointestinal (GI) tract could help HCU patients maintain healthy levels while easing natural protein restrictions. We describe the preclinical development of CDX-6512, a methionine gamma lyase (MGL) enzyme that was engineered for stability and activity within the GI tract for oral administration to locally degrade methionine. CDX-6512 is stable to low pH and intestinal proteases, enabling it to survive the harsh GI environment without enteric coating and to degrade methionine freed from dietary protein within the small intestine. Administering CDX-6512 to healthy non-human primates following a high protein meal led to a dose-dependent suppression of plasma methionine. In Tg-I278T Cbs-/- mice, an animal model that recapitulates aspects of HCU disease including highly elevated serum homocysteine levels, oral dosing of CDX-6512 after a high protein meal led to suppression in serum levels of both methionine and homocysteine. When animals received a daily dose of CDX-6512 with a high protein meal for two weeks, the Tg-I278T Cbs-/- mice maintained baseline homocysteine levels, whereas homocysteine levels in untreated animals increased by 39%. These preclinical data demonstrate the potential of CDX-6512 as an oral enzyme therapy for HCU.

Intracardiac amorphous tumor presenting in a patient with homocystinuria; a case report with literature review

Homocystinuria is a rare genetic disease with autosomal recessive pattern. It is reported to be highest in Arabian descend and could cause thrombosis, but mainly peripherally. Cardiac amorphous tumor has been recognized in the past 20 years and it is also a very rare cause primary benign tumor of the heart. Most of the cases reported to be associated with end-stage renal disease. Homocystinuria associated with Cardiac Amorphous tumor is extremely rare. Up to our knowledge, there has been only one other case has been reported. Our patient is a 14-year-old female known case of homocystinuria presented with dyspnea and leg edema. On workup was found to have a mass in the right atrium extending to superior vena cava and inferior cava. Surgery undertaken on cardiopulmonary bypass partial resection of the mass was done and result came back as cardiac amorphous tumor. We assume the cause of this sinister complication of her primary illness is calcification of thrombus as stated in literature. And also recommend further studies regarding issue on hand.

Allelic prevalence and geographic distribution of cerebrotendinous xanthomatosis

BACKGROUND

Cerebrotendinous xanthomatosis (CTX) is a rare recessive genetic disease characterized by disruption of bile acid synthesis due to inactivation of the CYP27A1 gene. Treatment is available in the form of bile acid replacement. CTX is likely underdiagnosed, and prevalence estimates based on case diagnosis are probably inaccurate. Large population-based genomic databases are a valuable resource to estimate prevalence of rare recessive diseases as an orthogonal unbiased approach building upon traditional epidemiological studies.

METHODS

We leveraged the Hardy-Weinberg principle and allele frequencies from gnomAD to calculate CTX prevalence. ClinVar and HGMD were used to identify high-confidence pathogenic missense variants and to calculate a disease-specific cutoff. Variant pathogenicity was also assessed by the VarSome implementation of the ACMG/AMP algorithm and the REVEL in silico predictor.

RESULTS

CTX prevalence estimates were highest in Asians (1:44,407-93,084) and lowest in the Finnish population (1:3,388,767). Intermediate estimates were found in Europeans, Americans, and Africans/African Americans (1:70,795-233,597). The REVEL-predicted pathogenic variants accounted for a greater increase in prevalence estimates for Europeans, Americans, and Africans/African Americans compared with Asians. We identified the most frequent alleles designated pathogenic in ClinVar (p.Gly472Ala, p.Arg395Cys), labeled pathogenic based on sequence consequence (p.Met1?), and predicted to be pathogenic by REVEL (p.Met383Lys, p.Arg448His) across populations. Also, we provide a prospective geographic map of estimated disease distribution based on CYP27A1 variation queries performed by healthcare providers from selected specialties.

CONCLUSIONS

Prevalence estimates calculated herein support and expand upon existing evidence indicating underdiagnosis of CTX, suggesting that improved detection strategies are needed. Increased awareness of CTX is important for early diagnosis, which is essential for patients as early treatment significantly slows or prevents disease progression.

Homocystinuria diagnosis and management: it is not all classical

Homocystinuria (HCU) refers to a group of inherited disorders of homocysteine metabolism associated with high blood homocysteine concentration, thromboembolic tendency and neurocognitive symptoms. The most common causes of a high blood homocysteine relate to underlying vitamin B12 or folate deficiency which must be excluded first. Thereafter, an inherited metabolic condition can be considered.The most prevalent inherited disorder of homocysteine metabolism is classical HCU caused by deficiency of the pyridoxine-dependent enzyme, cystathione beta-synthase, which converts homocysteine to cystathionine in the transsulphuration pathway. An alternative route for homocysteine metabolism is its remethylation to methionine by the cobalamin-dependent enzyme, methionine synthase, using the folate derivative, methyltetrahydrofolate, as a methyl donor. Remethylation defects are caused by impaired activity of methionine synthase itself, of an enzyme required to generate its methylcobalamin cofactor from dietary vitamin B12, or of the enzyme methyltetrahydrofolate reductase (MTHFR), which generates the methyl donor.The correct diagnosis can be inferred from additional laboratory investigations including a complete blood count and quantitation of methionine and methylmalonic acid. Methionine is high/normal in HCU and low in the remethylation disorders. In the latter, cobalamin defects are readily distinguished from MTHFR by a coexisting macrocytic anaemia and further delineated by presence or absence of methylmalonic acid in urine or plasma.Lowering homocysteine reverses thromboembolic risk. In HCU, this may be achieved with pyridoxine alone or with betaine as an alternative methyl donor. Some patients additionally follow a methionine-restricted diet. Betaine is the primary treatment for MTHFR and cobalamin disorders are managed with high-dose hydroxocobalamin.

Case report: Spontaneous bilateral intraocular lens dislocation in a patient with homocystinuria

Background

Spontaneous bilateral intraocular lens dislocation of the vitreous cavity is a rare ocular disorder. This article aims to comprehensively describe bilateral spontaneous intraocular lens dislocation with unilateral lamellar macular hole and retinoschisis in a Chinese woman with homocystinuria.

Case presentation

A 72-year-old Chinese woman with homocystinuria presented with a painless bilateral blurring of vision. The slit lamp showed the absence of lenses in both eyes. B-ultrasound and orbital computed tomography (CT) demonstrated bilateral posterior dislocation of the crystalline lenses, and spectral-domain optical coherence tomography (SD-OCT) revealed a lamellar macular hole and retinoschisis in the right eye. Biochemical examination demonstrated that the total homocysteine level was moderately elevated.

Conclusion

This report is the first to present an extensive and valuable description of bilateral intraocular lens dislocation with unilateral lamellar macular hole and retinoschisis secondary to homocystinuria. We have demonstrated that this case was spontaneous and chronic. CT is an effective diagnostic tool for patients with ectopia lentis. Early diagnosis and suitable management of patients with homocystinuria are essential to prevent these complications.

A case series of cerebral venous thrombosis as the first manifestation of homocystinuria

Background

Cerebral venous thrombosis (CVT) is an important cause of stroke particularly in younger patients and potentially fatal if diagnosis is delayed. The presentation of symptoms is highly variable and consequently the diagnosis and underlying cause is often delayed or overlooked. Homocystinuria, a rare autosomal recessive disorder is an identified risk factor for CVT.

Purpose

A timely diagnosis and treatment of the underlying cause of CVT could result in improved outcome and prevent further events. This case series describes the clinical course of six adults presented with unprovoked CVT, in whom the diagnosis of underlying homocystinuria was delayed with adverse consequences. We aim to highlight the importance of recognising homocystinuria as an underlying cause of CVT and offer a practical approach to the diagnosis and management.

Methods

This is a retrospective case series of a cohort of 30 consecutive patients seen in a UK tertiary referral centre.

Result

Six out of 30 patients presented with CVT prior to homocystinuria diagnosis. The mean and range of age at the time of the first CVT episode was 22.6 (range 11–31) years. The mean ±SD age at diagnosis of homocystinuria as the underlying cause was 26 ± 4.2 years. The time between first CVT and diagnosis of homocystinuria ranged from 1.6 to 11 years resulting in a delay to introduction of effective treatment and, in some cases, a further large vessels thrombotic event.

Conclusion

Physician awareness of homocystinuria as an underlying cause for an unprovoked CVT will facilitate timely introduction of effective treatment to prevent a further event.