The Journal of Bone and Joint Surgery, Vol 66, Issue 9 1408-1414, Copyright © 1984 by Journal of Bone and Joint Surgery, Inc
Pseudoachondroplasia: biochemical and histochemical studies of cartilage
A Pedrini-Mille, JA Maynard and VA Pedrini
Cartilage from patients with pseudoachondroplasia is characterized by
unique inclusions in the cisternae of the endoplasmic reticulum and
proteoglycan abnormalities have been suggested in this form of dwarfism. To
elucidate the nature of the proteoglycan defect, we determined the amount
of the individual glycosaminoglycans present in iliac-crest cartilage of
three patients and extracted the proteoglycan monomers from one of the
samples. Sections of iliac-crest cartilage and proximal fibular growth
plates were examined by electron microscopy and also stained with
hematoxylin and eosin, safranin O-fast green, and alcian blue in the
presence of increasing concentrations of magnesium chloride (zero to one
molar). The chondrocytes of the iliac crest and fibular physes were
arranged in clusters more than in columns and contained characteristic
endoplasmic reticulum inclusions, which were particularly large in the
hypertrophic cells. The cartilage stained very poorly with hematoxylin and
eosin and with safranin O-fast green. The alcian-blue stain was abolished
from perilacunar areas and from longitudinal septa by magnesium chloride
concentrations that were lower than those required by normal tissue. The
proteoglycans of iliac-crest cartilage were found to be significantly
enriched in keratan sulphate and had a below-normal ratio of
chondroitin-4-sulphate to chondroitin-6-sulphate, although the amount of
the two isomeric chondroitin sulphates combined was within normal limits.
The urinary excretion of glycosaminoglycan by the three patients was
normal. Pseudoachondroplasia appears to be a generalized cartilage disorder
involving abnormalities of proteoglycans, probably related to the core
protein or to enzymes that are responsible for the formation of the
glycosaminoglycan chains.(ABSTRACT TRUNCATED AT 250 WORDS)
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