Kniest dysplasia: radiologic, histopathological, and scanning electronmicroscopic findings.

We describe severe neonatal Kniest dysplasia. Radiological findings in a severe case include short bowed tubular bones with exaggerated metaphyseal flare, moderate platyspondyly with vertical clefts of the vertebral bodies, and characteristically shaped iliac bones. Pathologic findings included a disorganized physeal growth plate, soft crumbly cartilage with a "Swiss-cheese" appearance, and diastase resistant intracytoplasmic inclusions in the resting chondrocytes. Transmission electronmicroscopy showed dilated cisternae of rough endoplasmic reticulum with finely granular material of accumulated protein. Scanning electronmicroscopy documented striking fragmentation and disintegration of collagen fibrils resulting in a web-like pattern and large open cyst-like spaces, and deficiency and disorganization of the collagen fibrils.