Osteocraniostenosis-hypomineralized skull with gracile long bones and splenic hypoplasia. Four new cases with distinctive chondro-osseous morphology.

Osteocraniostenosis is a severe skeletal dysplasia characterized by a hypomineralized skull that has been previously described as kleeblattschädel (cloverleaf skull) and overtubulated long bones. Dysmorphic facial features include a short nose, short philtrum, and a small, inverted V-shaped mouth. Splenic a/hypoplasia is a constant finding. We report four infants (two unrelated and two siblings) with osteocraniostenosis and describe the clinical, radiographic and chondro-osseous morphology findings. The two siblings lack the moderate long-bone shortening that is typically seen. The skull configuration is likely caused by severely hypoplastic cranial bones (parietal) rather than true craniosynostosis, making the term "osteocraniostenosis" misleading. Histological examination of bone in all cases showed an abnormal growth plate with short irregular columns. The resting cartilage showed pleomorphic chondrocytes with increased cellularity and unique pseudocolumn formation. There are some radiographic and chondro-osseous morphologic similarities between osteocraniostenosis and severe Hallermann-Streiff syndrome (HSS), suggesting the two disorders may be pathogenetically related.