Case report: The spectrum of SMPD1 pathogenic variants in Hungary.

Acid sphingomyelinase deficiency (ASMD) is an autosomal recessive disease caused by biallelic pathogenic variants in the sphingomyelin phosphodiesterase-1 () gene. Acid sphingomyelinase deficiency is characterized by a spectrum of disease and is broadly divided into three types (ASMD type A, ASMD type A/B, and ASMD type B). More than 220 disease-associated variants have been reported, and genotype/phenotype correlations are limited. Here we report the first description of all six diagnosed acid sphingomyelinase deficiency cases in Hungary. Nine variants are present in this cohort, including 3 variants (G247D, M384R, and F572L), which have only been described in Hungarian patients. All described variants are deemed to be pathogenic. Eight of the variants are missense, and one is a frameshift variant. The treatment of an ASMD type A/B patient in this cohort using hematopoietic stem cell transplantation is also detailed. This study may help to support diagnosis, patient genetic counseling, and management of acid sphingomyelinase deficiency.