A novel SMPD1 mutation in two Chinese sibling patients with type B Niemann-Pick disease.

Type B Niemann-Pick disease is an autosomal recessive sphingolipidosis due to mutations in the sphingomyelin phosphodiesterase 1 gene (SMPD1). Here we present molecular findings for two sibling patients. One mutation V36A due to c.107T>C in exon 1 is a single nucleotide polymorphism and the other N522S due to c.1565 A>G in exon 6 is a novel missense mutation. This non-fatal missense mutation leads to –20% residual lysosomal acid sphingomyelinase activity in vitro and only results in hepatosplenomegaly without neurologic involvement.