PRINCIPLE OF METHOD: Hydrolysis of the synthetic substrate 4-methylumbelliferyl palmitate at acid pH and in the presence of Triton X100 to solubilise it is followed by measuring the fluorescence of the liberated 4-methylumbelliferone after stopping the reaction with alkaline buffer.
USES AND LIMITATIONS OF THE METHOD: The method is used for diagnosis of Wolman disease and its later onset variant cholesterol ester storage disease (CESD). Residual enzyme activity tends to be lower in the more severe disease, in both white cells and fibroblasts. Prenatal diagnosis is possible using CVS or amniocentesis but the laboratory does not offer carrier screening. Acid esterase is also low in fibroblasts from I-cell disease and pseudo-Hurler polydystrophy patients. The assay is included in our lysosomal enzyme screening procedure for patients with hepato(spleno)megaly.
SPECIMEN REQUIREMENTS: For preliminary testing, blood. 5 ml lithium heparin (orange capped tube) unseparated and unfrozen. Send at room temperature to arrive at the laboratory [hyperlink to main page] within 24h of venepuncture. For follow-up, fibroblasts cultured from a skin biopsy may be needed. Biopsy material should be collected aseptically into a sterile bottle containing tissue culture medium (available from the laboratory), and sent at room temperature to arrive within 24 hours. Biopsies for tissue culture should not be frozen. Fibroblast cultures established in other laboratories should be sent in plastic 25 cm2 flasks filled with medium.
THE LABORATORY RECOMMENDS USE OF A COURIER SERVICE OR ROYAL MAIL SPECIAL DELIVERY FOR SENDING ALL SPECIMENS TO THE LABORATORY.