Identification of a PROM1 mutation in a Spanish family with inherited retinal dystrophies

Background: We report a Spanish family, comprising an affected mother and daughter, respectively diagnosed with retinitis pigmentosa and Stargardt-like macular dystrophy, in whom we identified a PROM1 mutation. Methods: A custom gene panel consisting of 119 inherited retinal dystrophies (IRD)-genes was applied in the two affected individuals of this family and sequenced using the Illumina´s NextSeq500 platform. Results: The analysis of the resulting data allowed us to identify the pathogenic PROM1 mutation c.1117C>T (p.Arg373Cys) as the primary cause of the disease in both patients. No additional variants contributing to the extent of retinal dysfunction were detected. Conclusion: The variable expressivity of the detected PROM1 mutation is the most likely responsible for the intrafamilial phenotypic variability observed in this family. Screening of this mutation should be considered in patients with compatible clinical manifestations, especially when accompanied by an autosomal dominant family history.

Recognizing Atypical Dopa-Responsive Dystonia and Its Mimics

ABSTRACTPurpose of ReviewDopa-responsive dystonia (DRD) encompasses a group of phenotypically and genetically heterogeneous neurochemical disorders. Classic GTP cyclohydrolase 1 (GCH-1)-associated DRD consists of early-onset lower limb asymetrical dystonia, with sleep benefit, diurnal variation, and excellent and sustained response to low L-dopa doses.Recent findingsUnlike the classic phenotype, GCH-1-associated DRD may include features inconsistent with the original phenotype. We describe a GCH-1-associated late-onset DRD case with family history of parkinsonism and cervical dystonia whose response to levodopa was poor and complicated with dyskinesia, blepharospasm and severe non-motor symptoms. We use this case as a springboard to review the spectrum of atypical DRD, DRD-plus and DRD mimics.SummaryGCH-1-related dystonia may exhibit wide intrafamilial phenotypic variability, no diurnal fluctuation, poor response to L-dopa, and such complications as dyskinesia, epilepsy, sleep disorders, autonomic dysfunction, oculogyric crisis, myoclonus, or tics. More recently, rare GCH-1 variants have been found to be associated with Parkinson's disease. Clinicians should be aware of atypical DRD, DRD-plus and DRD mimics.

Intrafamilial Phenotypic Variability Associated with the I1739V Mutation in the SCN9A Gene

The SCN9A gene encodes a voltage gated sodium channel Nav1.7 in which mutations can result in a wide variety of phenotypes ranging from congenital insensitivity to pain to small fiber neuropathy. We report the genotype phenotype analysis in a family carrying a specific mutation, I1739V, in the SCN9A gene. Neurophysiological studies have documented the gain of function impact of this mutation on this sodium channel. Interestingly, there is significant interfamilial phenotypic variability in individuals carrying this mutation. In our family, a father daughter combination had identical genotypes analyzing the SCN9A gene and multiple other genes known to cause neuropathy. Both of them carry the I1739V mutation but exhibit significant phenotypic variability with complaints of decreased sensitivity to discomfort in the father while the daughter has the clinical and laboratory features consistent with a small fiber neuropathy. We hypothesize that there are modifiers of the I1739V mutation that could involve intronic or exonic gene variants which contribute to this intrafamilial phenotypic variability. Our study has implications for genetic counseling, personalized medicine and the development of drugs to treat neuropathic pain.