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Table 1 Classification of patients with ASMD based on historical terms

From: Disease manifestations and burden of illness in patients with acid sphingomyelinase deficiency (ASMD)

NPD type A Intermediate NPD, variant NPD B NPD type B
Phenotype: Infantile onset of severe neurodegeneration with progressive psychomotor deterioration
Natural history: uniform
Prognosis: death typically by 3 years of age
Phenotype: NPD B phenotype but also progressive neurologic findings including ataxia, variable degrees of developmental delay and peripheral neuropathy
Natural history: variable
Prognosis: patients live past early childhood, sometimes into adulthood
Phenotype: Chronic progressive multi-system disease with no or little neurologic involvement
Natural history: variable
Prognosis: variable (survival until the second to seventh decade of life)
  1. ASMD acid sphingomyelinase deficiency, NPD Niemann-Pick disease