Brachyolmia: radiographic and genetic evidence of heterogeneity.

Brachyolmia refers to a form of skeletal dysplasia characterized by general platyspondyly without significant epiphyseal, metaphyseal, or diaphyseal changes in the long bones. As a result of a study of 11 patients from 7 different families and a review of the literature we propose that there are 3 and possibly 4 different types of brachyolmia: 1. Hobaek type--an autosomal recessive condition with universal platyspondyly, irregular, and reduced intervertebral spaces and marked extension of the lateral margins of the vertebrae. Rectangular and elongated vertebral bodies are seen on lateral views of the spine, which become more pronounced with age. Toledo type--radiographically similar to Hobaek type but also associated with corneal opacities and precocious ossification of costal cartilage. It is uncertain as to whether this represents variability or heterogeneity. 2. Maroteaux type--an autosomal recessive disorder that is distinguished from Hobaek type by rounding of the anterior and posterior vertebral borders with less elongation on lateral view and less lateral extension on A.P. view. This type may be associated with precocious calcification of the falx cerebri, and minor facial anomalies. 3. Dominant type--a previously underscribed form which we have observed in a mother and her son. This type has the most severe vertebral changes with flattening and irregularities of the cervical spine. These clinical, radiological, and genetic differences suggest genetic heterogeneity in this group of platyspondylic disorders.