Acid Sphingomyelinase (Niemann-Pick A/B)
Related Gene(s): SMPD1
Niemann-Pick disease A/B is a lysosomal storage disease affecting approximately 1 in 250,000 people in the general population. The condition is inherited in an autosomal recessive pattern and caused by a deficiency of acid sphingomyelinase (ASM), which leads to the accumulation of sphingomyelin in the lysosomes of cells. This can cause the degradation and impairment of tissues and organs including the brain, lungs, spleen, and liver. Symptoms of the disease vary between type A and type B. Niemann-Pick disease A is neuronopathic, with symptoms including hepatosplenomegaly, neurologic deterioration, cherry-red spots in the macula of the retina, and respiratory failure with death by 3 years of age. Symptoms of Niemann-Pick disease B are less severe with later onset, usually do not involve the nervous system, and include hepatosplenomegaly, deterioration of pulmonary function, and osteopenia, with survival to adulthood.
The diagnosis of ASM deficiency is established either by demonstration of deficiency of ASM enzyme (less than 10%) or identification of biallelic pathogenic SMPD1 mutations. The ASM activity is measured with a lysate from patient’s white blood cells (WBC) using a liquid chromatography and tandem mass spectrometry (LC-MS/MS) method. However, gene carrier status is detected through molecular analysis of the SMPD1 gene through targeted analysis for pathogenic variants in the gene or sequence analysis.
- Blood: 5-10 mL in ACD tube (yellow top) is preferred. Minimum of 3 mL is required. Sodium (or lithium) heparin tubes (green top) or EDTA tubes (lavender top) are also accepted
- 1-2 leukocyte pellets
- Ship whole blood at room temperature; sample must be received within 72 hours of collection
- Ship leukocyte pellet(s) frozen on dry ice
- 7 days