Applications of a new fluorimetric enzyme assay for the diagnosis of aspartylglucosaminuria

L-Aspartic acid-β-7-amido-4-methylcoumarin is a sensitive and specific fluorogenic substrate for lysosomal glycoasparaginase (aspartylgluco-saminidase). Fibroblasts and leukocytes from 8 patients with aspartylglucosaminuria, showed 1-7% of the mean normal glycoasparaginase activity. Heterozygotes showed intermediate activities. Glycoasparaginase activity in chorionic villi, cultured trophoblasts, cultured amniotic fluid cells and amniotic fluid was readily detectable, indicating that prenatal analysis of aspartylglucosaminuria should be possible with this assay. β-Aspartyl-4-methylumbelliferone was synthesized but this potential substrate can not be used to assay glycoasparaginase since it hydrolyses spontaneously

β-Mannosidase deficiency: Heterogeneous manifestation in the first female patient and her brother

Summary β-Mannosidase deficiency was demonstrated in fibroblasts of a girl who showed severe psychomotor retardation, bone deformities and gargoylism and recurrent skin and r

Diagnosing mucopolysaccharidosis IVA

Mucopolysaccharidosis IVA (MPS IVA; Morquio A syndrome) is an autosomal recessive lysosomal storage disorder resulting from a deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS) activity. Diagnosis can be challenging and requires agreement of clinical, radiographic, and laboratory findings. A group of biochemical genetics laboratory directors and clinicians involved in the diagnosis of MPS IVA, convened by BioMarin Pharmaceutical Inc., met to develop recommendations for diagnosis. The following conclusions were reached. Due to the wide variation and subtleties of radiographic findings, imaging of multiple body regions is recommended. Urinary glycosaminoglycan analysis is particularly problematic for MPS IVA and it is strongly recommended to proceed to enzyme activity testing even if urine appears normal when there is clinical suspicion of MPS IVA. Enzyme activity testing of GALNS is essential in diagnosing MPS IVA. Additional analyses to confirm sample integrity and rule out MPS IVB, multiple sulfatase deficiency, and mucolipidoses types II/III are critical as part of enzyme activity testing. Leukocytes or cultured dermal fibroblasts are strongly recommended for enzyme activity testing to confirm screening results. Molecular testing may also be used to confirm the diagnosis in many patients. However, two known or probable causative mutations may not be identified in all cases of MPS IVA. A diagnostic testing algorithm is presented which attempts to streamline this complex testing process

A Fatal, Systemic Mitochondrial Disease with Decreased Mitochondrial Enzyme Activities, Abnormal Ultrastructure of the Mitochondria and Deficiency of Heat Shock Protein 60

We report on a girl presenting with facial dysmorphic features and breathing difficulties upon birth. She was hypotonic, developed a metabolic acidosis, and died two days old of heart failure. Post-mortem examination revealed abnormalities of brain, lungs, heart and liver. In cultured skin fibroblasts activities of enzymes of oxidative phosphorylation, pyruvate metabolism, beta-oxidation and other mitochondrial (mt) metabolic pathways were markedly decreased. Activities of enzymes localized in the mt outer membrane or in other cell organelles were found to be normal. The mitochondria appeared swollen and were located mainly around the nucleus. Electron micrographs showed locally disintegrated mt inner membranes and large mt vacuoles. The amount of mt heat shock protein 60 (hsp60) was about one fifth of that in controls. We conclude that this mt disorder is most likely caused by defective synthesis and maintenance of mitochondria, possibly due to a defect in mt protein import or enzyme assembly resulting from deficiency of hsp60.

The natural course of infantile Pompe's disease: 20 original cases compared with 133 cases from the literature

Objective. Infantile Pompe's disease is a lethal cardiac and muscular disorder. Current developments toward enzyme replacement therapy are promising. The aim of our study is to delineate the natural course of the disease to verify endpoints of clinical studies. Methods. A total of 20 infantile patients diagnosed by the collaborative Dutch centers and 133 cases reported in literature were included in the study. Information on clinical history, physical examination, and diagnostic parameters was collected. Results. The course of Pompe's disease is essentially the same in the Dutch and the general patient population. Symptoms start at a median age of 1.6 months in both groups. The median age of death is 7.7 and 6 months, respectively. Five percent of the Dutch patients and 8% of all reported patients survive beyond 1 year of age. Only 2 patients from literature became older than 18 months. A progressive cardiac hypertrophy is characteristic for infantile Pompe's disease. The diastolic thickness of the left ventricular posterior wall and cardiac weight at autopsy increase significantly with age. Motor development is severely delayed and major developmental milestones are generally not achieved. For the Dutch patient group, growth deviates significantly from normal despite start of nasogastric tube feeding. Levels of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, creatine kinase, or creatine kinase-myocardial band isoenzyme are typically elevated, although aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase increase significantly with age. The patients have fully deleterious mutations. Acid alpha-glucosidase activity is severely deficient. Conclusions. Survival, decrease of the diastolic thickness of the left ventricular posterior wall, and achievement of major motor milestones are valid endpoints for therapeutic studies of infantile Pompe's disease. Mutation analysis and measurement of the alpha-glucosidase activity should be part of the enrollment progra