Infantile spasms in early-onset Niemann-Pick disease with a novel compound heterozygous mutations in SMPD1 gene.

Niemann-Pick diseases are a group of rare autosomal recessive disorders caused by an inherited deficiency of lysosomal storage with similar clinical presentations. At least three different Niemann-Pick (NP) diseases have been described, with NPA and NPB occurring as a result of a deficiency of the acid sphingomyelinase (ASM) enzyme, while NPC as a disorder that cause misregulation in cholesterol and lipids turnover, causing their accumulation in various tissues, including brain. The resulting phenotypic spectrum ranges from a severe infantile type with neurologic degeneration and death, usually by 3 years of age (NPA), to a non-neurologic adult onset form compatible with survival into adulthood (NPB) and a neurovisceral disorder with symptoms that occur at different times and progress independently (NPC). Here, we report on an Italian child born from non-consanguineous healthy parents, with a negative family history, who developed infantile spasms at the age of 5 months and clinical signs of potential storage disease. The genetic screening, performed by means of whole exome sequencing, revealed compound heterozygous mutations in the Sphingomyelin Phosphodiesterase 1 gene (SMPD1), comprising both a homozygous polymorphism (p.V36A) in exon 1 and a new frameshift heterozygous deletion (c.1187delT) in exon 3 generating a premature stop (TAA) at codon 424 (p.L395fsX29). This result appears to corroborate the phenotypic heterogeneity of the symptoms and suggests a correlation between the presence of a truncated SMPD1 polypeptide and the very early onset of the disease.