👤 Giuliana Silvestri

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare inherited white matter disorder. Initially, a "classic" phenotype has been characterized, presenting early-onset macrocephaly, cerebellar ataxia, mild spasticity, and a distinctive neuroimaging pattern of diffuse white matter abnormalities with subcortical cysts. An "improving" phenotype has also been described, featuring milder or absent neurological signs and a remitting pattern on neuroimaging. Mutations in four genes, MLC1, HEPACAM, GPRC5B and AQP4 have been associated with MLC. We describe clinical and genetic features of a cohort of genetically confirmed Italian MLC patients, representing the largest Italian cohort reported to date. We conducted a retrospective, multicenter, observational study. Patients were included based on clinical and neuroimaging features consistent with MLC, along with a confirmed genetic diagnosis. Data were collected using a standardized database and included demographic, clinical, neuroimaging, neurophysiological, and genetic information. Thirty-three patients from eight Italian centers were enrolled. Twenty-seven harbored biallelic MLC1 variants (23 distinct mutations, including three novel variants), while six had three distinct heterozygous HEPACAM variants. All MLC1-mutated patients exhibited the "classic" phenotype, frequently accompanied by orthopedic, gastrointestinal, and respiratory comorbidities. HEPACAM-mutated patients were consistent with the "improving" phenotype. No patients harbored mutations in GPRC5B or AQP4. Our findings expand the mutational spectrum of MLC1, further characterize the disease phenotype, and provide valuable insights into its presence in Italy. They also underscore management needs of individuals with MLC, highlighting the importance of multidisciplinary care. Show less

Retinitis pigmentosa (RP) is a devastating form of retinal degeneration, with significant social and professional consequences. Molecular genetic information is invaluable for an accurate clinical diagnosis of RP due to its high genetic and clinical heterogeneity. Using a gene capture panel that covers 163 of the currently known retinal disease genes, including 48 RP genes, we performed a comprehensive molecular screening in a collection of 123 RP unsettled probands from a wide variety of ethnic backgrounds, including 113 unrelated simplex and 10 autosomal recessive RP (arRP) cases. As a result, 61 mutations were identified in 45 probands, including 38 novel pathogenic alleles. Interestingly, we observed that phenotype and genotype were not in full agreement in 21 probands. Among them, eight probands were clinically reassessed, resulting in refinement of clinical diagnoses for six of these patients. Finally, recessive mutations in CLN3 were identified in five retinal degeneration patients, including four RP probands and one cone-rod dystrophy patient, suggesting that CLN3 is a novel non-syndromic retinal disease gene. Collectively, our results underscore that, due to the high molecular and clinical heterogeneity of RP, comprehensive screening of all retinal disease genes is effective in identifying novel pathogenic mutations and provides an opportunity to discover new genotype-phenotype correlations. Information gained from this genetic screening will directly aid in patient diagnosis, prognosis, and treatment, as well as allowing appropriate family planning and counseling. Show less