Acid sphingomyelinase deficiency: Phenotypic, biochemical, and molecular heterogeneity in a series of 47 Iraqi patients from a single center

Objectives Acid sphingomyelinase deficiency (ASMD) is an inherited autosomal recessive disease caused by pathogenic variants in the sphingomyelin phosphodiesterase-1 (SMPD1) gene, which encodes acid sphingomyelinase (ASM). ASMD has 3 broad phenotypes (type A, type A/B, and type B) characterized by the age of onset, symptomatology, and the rapidity of disease progression. The diagnosis of ASMD can be delayed or missed because of the wide spectrum of severity and its variable manifestations. Analysis of genotype-phenotype correlations can help to determine ASMD disease type and inform management. Here, we describe the clinical presentation of 47 patients with ASMD referred to a single center in Iraq since 2007, whose diagnosis was confirmed by gene sequencing and ASM activity. Study design This was a retrospective observational cohort study of patients diagnosed with ASMD in Iraq. Results The cohort included 47 patients with ASMD. A positive family history and consanguinity were noted in 66% and 98% of these cases, respectively. Hepatosplenomegaly, anemia, and thrombocytopenia were present in 100%, 79%, and 44% of patients, respectively. Notably, dysmorphic features were observed in 23% of cases. Thirteen SMPD1 variants were present in this cohort, the most common of which were c.1556A > G (p.Tyr519Cys), c.740delG (p.Gly247Alafs*10), c.967A > C (p.Ser323Arg), and c.1267C > T (p.His423Tyr). Three of the variants identified were novel, specifically c.967A > C (p.Ser323Arg), c.1579A > G (p.Asn527Asp), and c.905C > T (p.Thr302Ile). Conclusions Physicians assessing infants and children who present with hepatosplenomegaly or anemia and dysmorphic features should have a high index of suspicion for ASMD, particularly in regions with high rates of consanguineous unions.