Advances in human genetics. 5 / edited by Harry Harris and Kurt Hirschhorn.

Date:
1975
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Advances in human genetics. 5 / edited by Harry Harris and Kurt Hirschhorn. Source: Wellcome Collection.

    51/408 (page 33)
    Chapter 1 : The Chondrodystrophies 33 progression of proliferating to hypertrophic cells, but the columns are shorter and wider than normal, and the cells are larger than normal and stain intensely with alcian blue. In some cases, there is a focal disruption of the growth plate by areas of fibrous tissue continuous with the cysts present within the resting cartilage. Thus diastrophic dwarfism appears to be a generalized, degenerative disorder of cartilage with focal death of cells followed by matrix dissolution, cyst formation, fibrovascular scarring, and dystrophic ossification. The increased size of the chondrocytes and the abnormal perilacunar staining suggest that the basic defect in diastrophic dwarfism may be a metabolic defect in chondrocyte metabolism, resulting in early cell death. Diastrophic dwarfism is inherited as an autosomal recessive trait. Several disastrous errors in genetic counseling have been made by confusing this disorder with achondroplasia, which is inherited as an autosomal dominant trait. The clinical and radiographic features of diastrophic dwarfism are quite distinctive and there should be no difficulty in making an accurate diagnosis of this disorder. Diastrophic Variant A syndrome which is similar but apparently distinct from diastrophic dwarfism has recently been delineated and has been called the diastrophic variant (Fig. 6A). We have observed two unrelated patients with this dis¬ order, and Walker et included two patients with the variant in their extensive series of diastrophic dwarfs. The diastrophic variant resembles diastrophic dwarfism qualitatively, but is much milder in severity. These individuals are not severely dwarfed, with heights usually greater than 55 inches. They are a number of clinical features in common with diastrophic dwarfs, such as club feet, external ear deformities, hand anomalies, and peculiar facies, but the number of anomalies present and their severity are quite variable from patient to patient. Radiographic changes have also been quite variable in this disorder, but abnormalities have been found similar to those seen in diastrophic dwarfism, including short, twisted, bowed long bones, disproportionate shortening of radius and ulna, metaphyseal flaring, radial head dislocation, and short metacarpals and phalanges (Fig. 6B). In one of our cases, symphalangism was not present. The spine showed slight interpedicular narrowing in L5-S1, and posterior scalloping of the vertebrae. Spina bifida occulta was also observed in the cervical spine. Coxa vara and irregularity of the femoral heads were present. Thus the radiographic changes