Enzymatic Screening and Diagnosis of Lysosomal Storage Diseases.
Lysosomal storage diseases (LSDs) are a group of more than 50 genetic disorders. Clinical symptoms are caused by the deficiency of specific enzyme (enzymes) function and resultant substrate accumulation in the lysosomes, which leads to impaired cellular function and progressive tissue and organ dysfunction. Measurement of lysosomal enzyme activity plays an important role in the clinical diagnosis of LSDs. The major enzymatic testing methods include fluorometric assays using artificial 4-methylumbelliferyl (4-MU) substrates, spectrophotometric assays and radioactive assays with radiolabeled natural substrates. As many effective treatment options have become available, presymptomatic diagnosis and early intervention are imperative. Many methods were developed in the past decade for newborn screening (NBS) of selective LSDs in dried blood spot (DBS) specimens. Modified fluorometric assays with 4-MU substrates, MS/MS or LC-MS/MS multiplex enzyme assays, digital microfluidic fluorometric assays, and immune-quantification assays for enzyme contents have been reported in NBS of LSDs, each with its own advantages and limitations. Active technical validation studies and pilot screening studies have been conducted or are ongoing. These studies have provided insight in the efficacy of various methodologies. In this review, technical aspects of the enzyme assays used in clinical diagnosis and NBS are summarized. The important findings from pilot NBS studies are also reviewed.
Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029.
Chunli
C
Yu
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030.
Qin
Q
Sun
Newborn Screening and Molecular Biology Branch, Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341.
Hui
H
Zhou
lysosomal enzyme; lysosomal storage diseases (LSDs); newborn screening (NBS); tandem mass spectrometry (MS/MS)