Joan M Keutzer

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The mucopolysaccharidoses (MPSs) often present a diagnostic challenge, particularly for patients who have more slowly progressive disease phenotypes, as early disease manifestations can be subtle or non-specific. However, certain types of bone and joint involvement should always prompt consideration of an MPS diagnosis, such as early joint involvement(More)
Glucocerebrosidase (GBA) mutations have been associated with Parkinson's disease in numerous studies. However, it is unknown whether the increased risk of Parkinson's disease in GBA carriers is due to a loss of glucocerebrosidase enzymatic activity. We measured glucocerebrosidase enzymatic activity in dried blood spots in patients with Parkinson's disease(More)
BACKGROUND Reports of the use of multiplex enzyme assay screening for Pompe disease, Fabry disease, Gaucher disease, Niemann-Pick disease types A and B, and Krabbe disease have engendered interest in the use of this assay in newborn screening. We modified the assay for high-throughput use in screening laboratories. METHODS We optimized enzyme reaction(More)
OBJECTIVE Pompe disease causes progressive, debilitating, and often life-threatening musculoskeletal, respiratory, and cardiac symptoms. Favorable outcomes with early intravenous enzyme-replacement therapy and alglucosidase alfa have been reported, but early clinical diagnosis before the development of severe symptoms has rarely been possible in infants. (More)
BACKGROUND Lysosomal storage disorders (LSDs) comprise more than 40 genetic diseases that result in the accumulation of products that would normally be degraded by lysosomal enzymes. A tandem mass spectrometry (MS/MS)-based method is available for newborn screening for 5 LSDs, and many laboratories are initiating pilot studies to evaluate the incorporation(More)
BACKGROUND Mucopolysaccharidosis type I (MPS I) is a genetic disease caused by the deficiency of α-L-iduronidase (IDUA) activity. MPS I is classified into three clinical phenotypes called Hurler, Scheie, and Hurler-Scheie syndromes according to their clinical severity. Treatments for MPS I are available. Better outcomes are associated with early treatment,(More)
BACKGROUND Late-onset Pompe disease (LOPD) is a rare treatable lysosomal storage disorder characterized by progressive lysosomal glycogen accumulation and muscle weakness, with often a limb-girdle pattern. Despite published guidelines, testing for LOPD is often overlooked or delayed in adults, owing to its low frequency compared to other muscle disorders(More)
Short-chain C6-sphingomyelin is an artificial substrate that was used in an acid sphingomyelinase activity assay for a pilot screening study of patients with Niemann-Pick disease types A and B. Using previously published multiplex and single assay conditions, normal acid sphingomyelinase activity levels (i.e. false negative results) were observed in two(More)
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