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ASMD Diagnosis

Gaucher disease and acid sphingomyelinase deficiency, or ASMD, are rare inherited lysosomal disorders affecting the metabolism of sphingolipids within the lysosome. Both are categorized as rare diseases. The incidence of Gaucher disease is 1 in 50,000 to 1 in 100,000 live births worldwide, and ASMD is estimated to affect 0.5 per 100,000 live births.

Given both conditions are under-recognized, particularly ASMD, and both have several of the same differential diagnoses, it is recommended that patients with clinical suspicion of Gaucher Disease also be tested for ASMD.

 

Enzyme Activity

Gaucher Disease: Glucocerebrosidase enzyme assay1:

  • Adults: usually 10% to 30% of normal
  • Children (severe cases) < 10% of normal
  • Residual activity does not predict clinical outcome

ASMD: Acid Sphingomyelinase enzyme assay:

  • <10% residual activity
  • Residual activity does not predict clinical outcome
  • Consider ordering in parallel, or if glucocerebrosidase is normal2

 

Genetic Testing (DNA Sequencing)

Gaucher Disease: GBA gene sequencing:

  • Two pathogenic variants in trans
  • Six variants account for 97% of all pathogenic variants in patients of Ashkenazi heritage3: N370S, R496H, V394L, 84insG, A→1G+IVS2, and L444P
  • N370S is neuroprotective

ASMD: SMPD1 gene sequencing:

  • Two pathogenic variants in trans4
  • ΔR610 is considered to be neuroprotective, common in chronic visceral form in multiple ethnic groups

 




1. McGovern MM, et al. Genet Med. 2017;19(9):967-974
2. McGovern MM, et al. Orphanet J Rare Dis. 2017;12(1):41
3. McGovern MM, Wasserstein MP, Giugliani R, et al. Pediatrics. 2008;122(2):341-349
4. Schuchman EH. J Inherit Metab Dis. 2007;30(5):654-663
5. McGovern M, Lippa N, Bagiella E, et al. Genet Med. 2013;15(8):618-623

 

 

Last Updated: Feb 7, 2021
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