The conditions to be described in this group of lesions are generalized skeletal abnormalities characterized by dwarfism affecting the spine and limbs, visceral abnormalities and evidence of a lysosomal storage disorders involving mucopolysaccharide or mucolipid.
In some the skeletal changes predominate, in others the visceral changes. Hunter first described a developmental abnormality in two brothers and Hurler recognized a hereditary component and that it was a primary disturbance of skeletal growth.
The finding of acid mucopolysaccharides or glycosaminoglycans in the urine of a number of patients with diseases with skeletal and visceral manifestations of common form resulted in the concept of mucopolysaccharidosis.
McKusick divided mucopolysaccharidoses into six types according to the mucopolysaccharide involved and the clinical and radiological features.
Expansion of research into the biochemical basis of these diseases has led to a modification of the classification, the recognition of additional syndromes and the differentiation of a group of diseases with many features, especially the skeletal ones, similar to those of mucopolysaccharidoses but with abnormal storage of muscopolysaccharides.
Investigation of the urinary mucopolysaccharide could help to establish the diagnosis in doubtful cases.
Biochemical analysis using tests such as uronic acid-creatinine ratios and cetylpyridinium chloride turbidity have improved diagnostic testing yet further.
Additional and valuable information has been derived from the finding that the cultured fibroblasts from a skin biopsy manifest the disease by accumulating excessive amounts of mucopolysaccharide and that this accumulation can be reduced to near normal when the patient’s cells are supplied with secretions from fibroblasts from normal persons.
In the true mucopolysaccharidoses, excretion of glycosaminoglycan, which is normally 15 milligrams per day, exceeds this to levels as high as 100 milligrams or more.
All investigations indicate that the basic cause of mucopolysaccharidosis is defective degradation of glycosaminoglycan with abnormal lysosomal storage. Because of the diffuse distribution of connectie tissues, changes involve bone, cartilage, skin, meninges, liver, spleen, blood vessels and other tissues.
Mental defect, which is a feature of many mucopolysaccharidoses, is associated with deposition of gangliosides in the nervous system.
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