Mucolipidosis III. Pseudo-Hurler polydystrophy. N-acetylglucosaminyl-1-phosphotransferasa deficiency.
Incidence
Rare autosomal recessive condition.
Clinical Characteristics
This rare autosomal recessive condition share the same pathogenic mechanism with I-cell disease or mucolipidosis II but the clinical picture is much mildler and survival into adulthood is not unusual. Mucolipidosis III is characterized by dwarfism, skeletal abnormalities reminiscence of Morquio disease with severe involvement of bones of the pelvis, scapula and hands, a moderate dysmorphic appearance, corneal opacities and in some patients retinal degeneration and aortic insufficiency. There are multiple flexion-ankylosis of the fingers and reduced mobility of other joints. No urinary excretion of mucopolysaccharides is detectable. The level of lysosomal hydrolases in the serum is elevated. Approximately half of the patients have some degree of learning disability or moderate mental retardation. Carpal tunnel syndrome may occur. The activity of N-acetyl-phosphotransferase in leukocytes and cultured fibroblasts is less severely depressed than in mucolipidosis II. Hepatomegaly may occur. Splenomegaly may occur. Vacuolated lymphocytes tend to be present Symptoms start at the age of two to forty years and patients progress into adulthood. There is dysostosis multiplex with vertebral changes and osteolysis with osteonecrosis. There are no seizures. In summary, the biochemical abnormalities in mucolipidosis III are similar in those seen in I-cell disease but symptoms do not begin until after the age of two years and mental retardation is mild to moderate. Growth retardation occur and radiographic examination show a pattern of dysostosis multiplex with severe pelvic and vertebral abnormalities. Mild corneal opacities are present and valvular heart disease is common. The disease is diagnosed by enzyme assay in leukocytes and cultured fibroblasts.
Precipitants
no
Provocation Tests
no
Diagnostic Procedures
EB-F, EB-W. The disease is diagnosed by enzyme assay in leukocytes and cultured fibroblasts.The activity of N-acetyl-phosphotransferase in leukocytes and cultured fibroblasts is less severely depressed than in mucolipidosis II. Vacuolated lymphocytes tend to be present. No urinary excretion of mucopolysaccharides is detectable.