Novel retinal findings in peroxisomal biogenesis disorders

Identification of novel compound heterozygous variants in the PEX10 gene in a Han-Chinese family with PEX10-related peroxisome biogenesis disorders

The peroxisome biogenesis disorders (PBDs) are a group of rare inherited autosomal recessive diseases characterized by motor and cognitive neurological dysfunction, hypotonia, seizures, feeding difficulties, retinopathy, sensorineural hearing loss, hepatic and renal abnormalities, and chondrodysplasia punctata of long bones, and the clinical expression is variable. Exome sequencing and Sanger sequencing were used to identify the genetic defect for PBDs in a two-generation non-consanguineous Han-Chinese pedigree. Compound heterozygous variants, a novel splicing variant c.113-2A>G and a reported substitution c.890T>C (p.Leu297Pro), in the peroxisomal biogenesis factor 10 gene (PEX10) were detected. The splicing variant c.113-2A>G led to a canonical splice acceptor site inactivation, exon 2 skipping, and in-frame deletions (p.Ala39_Gly65del). The three patients had similar phenotypes of milder PBDs, which were further genetically determined as PBD6B. The findings extend the PEX10 variant spectrum and may provide new insights into PBDs causation and diagnosis, with implications for genetic counseling and clinical management.

Congenital retinal folds

Congenital retinal folds (CRFs) are a rare entity, with an incompletely understood pathogenesis. They are often associated with ocular conditions such as familial exudative vitreoretinopathy (FEVR). We present a series of 5 patients with unilateral CRFs who underwent genetic testing. Mutations were identified in 4 patients: FZD4 and TSPAN12, both associated with FEVR, and IMPDH1 and PEX1, whose roles in CRF are unclear. Four patients presented with strabismus, all of whom underwent surgical intervention. Two patients developed tractional retinal detachments that necessitated vitrectomy. Visual outcomes were generally poor, with final visual acuity ranging from 20/600 to no light perception. This series underscores the importance of genetic testing in CRF cases, particularly for assessing familial risk, although the genetic basis remains inconclusive. Patients should be closely monitored for complications such as retinal detachment.

Characterization of Severity in Zellweger Spectrum Disorder by Clinical Findings: A Scoping Review, Meta-Analysis and Medical Chart Review

Zellweger spectrum disorder (ZSD) is a rare, debilitating genetic disorder of peroxisome biogenesis that affects multiple organ systems and presents with broad clinical heterogeneity. Although severe, intermediate, and mild forms of ZSD have been described, these designations are often arbitrary, presenting difficulty in understanding individual prognosis and treatment effectiveness. The purpose of this study is to conduct a scoping review and meta-analysis of existing literature and a medical chart review to determine if characterization of clinical findings can predict severity in ZSD. Our PubMed search for articles describing severity, clinical findings, and survival in ZSD resulted in 107 studies (representing 307 patients) that were included in the review and meta-analysis. We also collected and analyzed these same parameters from medical records of 136 ZSD individuals from our natural history study. Common clinical findings that were significantly different across severity categories included seizures, hypotonia, reduced mobility, feeding difficulties, renal cysts, adrenal insufficiency, hearing and vision loss, and a shortened lifespan. Our primary data analysis also revealed significant differences across severity categories in failure to thrive, gastroesophageal reflux, bone fractures, global developmental delay, verbal communication difficulties, and cardiac abnormalities. Univariable multinomial logistic modeling analysis of clinical findings and very long chain fatty acid (VLCFA) hexacosanoic acid (C26:0) levels showed that the number of clinical findings present among seizures, abnormal EEG, renal cysts, and cardiac abnormalities, as well as plasma C26:0 fatty acid levels could differentiate severity categories. We report the largest characterization of clinical findings in relation to overall disease severity in ZSD. This information will be useful in determining appropriate outcomes for specific subjects in clinical trials for ZSD.