Chronic acid sphingomyelinase deficiency diagnosed in infancy/childhood in Polish patients: 2024 update.

Background: Acid sphingomyelinase deficiency (ASMD) is an autosomal recessive lysosomal storage disease (LSD) associated with biallelic pathogenic variants in the sphingomyelin phosphodiesterase 1 (SMPD1) gene.

Objectives: The aim of this study was to provide the 2024 update on chronic visceral and neurovisceral ASMD diagnosed in the infancy/childhood in Polish patients.

Material and methods: All the patients diagnosed in the pediatric age (0-18 years) with ASMD, both chronic neurovisceral and visceral type, and then systematically followed up, were enrolled into the study.

Results: A total number of 7 patients were enrolled into the study. Four patients were previously reported. Two patients were newly recognized with ASMD - 1 with chronic visceral and 1 with chronic neurovisceral ASMD. Splenomegaly was noted in all the patients while a mild liver enlargement was observed in 4 of 7 patients. All patients presented with decreased high-density lipoprotein cholesterol (HDL-C) and decreased serum 25-hydroxy-vitamin D concentration while almost all (6 of 7) with hypercholesterolemia. Cherry-red spot was observed in 5 of 7 patients, including 1 patient with neurovisceral type. Seven various SMPD1 gene variants were identified and missense variants were the most common types of genetic lesions, comprising 71% of all alleles. In all the screened patients, lyso-sphingomyelin (lyso-SM) in dried blood spot (DBS) was found elevated; however, the greater values were observed for patients with chronic neurovisceral type.

Conclusion: Chronic acid sphingomyelinase deficiency (ASMD) is a slowly progressive disease. Pediatric ASMD is characterized by spleno-hepatomegaly, dyslipidemia (with decreased HDL-C as the most characteristic) and infiltrative (interstitial) lung disease. Both visceral and neurovisceral chronic ASMD patients could present with cherry-red spot. Both acid spingomyelinase activity and lyso-spingomyelin concentration in DBS should be regarded as a first-tier screening method into ASMD.