The p.Ala1035Val variant in Niemann-Pick type C1: Clinical and molecular characterization in Brazilian and Portuguese...

Niemann-Pick disease type C1 (NPC1, OMIM 257220) is a rare, progressive, and fatal autosomal recessive lysosomal storage disorder caused by pathogenic variants in the NPC1 gene. These variants disrupt intracellular lipid trafficking, leading to the accumulation of cholesterol and glycosphingolipids and resulting in severe, multisystem dysfunction for which no cure currently exists.

To investigate the potential founder effect and shared ancestry of the p.Ala1035Val variant, we analyzed 30 genetically confirmed NPC1 cases, comprising 18 Brazilian (12 of whom were homozygous) and 12 Portuguese participants (3 of whom were homozygous), each carrying at least one p.Ala1035Val allele. Diagnosis was established by clinical evaluation, biochemical assays, and filipin staining, with molecular confirmation by NPC1 genotyping.

All analyzed individuals exhibited a conserved haplotype across the SNVs in exons 6 (c.644 A > G, p.His215Arg), 12 (c.1926G > C, p.Ile642Met), 17 (c.2572 A > G, p.Ile858Val), and 18 (c.2793C > T, p.Asn931=), strongly supporting a shared founder effect consistent with an Iberian-associated ancestral background. Among Brazilian (n = 14), visceral involvement occurred in 10/14 (71.4%), predominantly hepatosplenomegaly (6/14, 42.9%), and developmental/cognitive alterations in 10/14 (71.4%), followed by ataxia or gait disturbance in 4/14 (28.6%). Among the Portuguese (n = 3), all presented with visceral involvement, characterized by hepatosplenomegaly (3/3, 100%); one had developmental delay (1/3, 33.3%), and none exhibited ataxia/gait disturbance. Despite the small sample size, clinical patterns appeared similar between the two groups, with differences likely reflecting sampling variability.

These findings expand the known variant spectrum of NPC1 in Brazilian and Portuguese populations, supporting a possible founder effect resulting from Portuguese colonisation. They also highlight the clinical value of haplotype analysis as a tool for tracing disease origin and improving stratification in medical settings. Furthermore, they emphasise the importance of refining early diagnostic strategies to optimise patient management and improve outcomes in NPC, while highlighting the need for larger, multicenter studies to corroborate this hypothesis and refine its clinical and genetic implications.