A new type of achondrogenesis

Lethal osteosclerotic skeletal dysplasia with intracellular inclusion bodies

We report an apparently previously undescribed form of lethal osteosclerotic skeletal dysplasia in a 30-week male fetus with micromelic shortness of the limbs. Radiographic findings at necropsy included increased density in all bones, most marked in the skull, mandible, and pubis. The ribs were very short, abnormally modeled, and wide anteriorly. The vertebrae were posteriorly hypoplastic and wedged, particularly in the cervical and lumbar regions. The femora and tibiae were short with wide distal metaphyses, undermodeled diaphyses, and coxa vara. The humeri, radii, and ulnae were also short and undermodeled with proximal and distal flare. Chondro-osseous morphology showed short chondrocyte columns, extension of hypertrophic cells into the metaphysis, and overgrowth of perichondral bone. In the resting cartilage there were large chondrocytes containing a homogeneous material staining pink with von Kossa trichrome, gray with toluidine blue, and black with silver methenamine. The cortical bone was lacking and the trabecular bone was hypercellular, thick, and coarse. Ultrastructurally, the resting zone chondrocytes were large and round with condensed chromatin and dilated loops of rough endoplasmic reticulum. The radiographic and histopathologic findings in this case are unique and differ from those seen in other reported lethal osteosclerotic skeletal dysplasias.

Case report 693: Schneckenbecken dysplasia

Three siblings with SBD from consangineous parents are reported. The prenatal diagnosis of a short-limbed form of dwarfism was made by ultrasonography and the final diagnosis in the index case by radiography, demonstrating a short-limbed, platyspondylic dwarf with a snail-like configuration of the ilium and vertebral bodies, flat on AP and round on lateral view. The histological examination showed a generalized, severe disturbance of cartilage formation with marked hypercellularity of proliferating and resting zones, reduction of intercellular matrix, and shortening of the irregular columns of proliferating cartilage. The ultramicroscopic findings were nonspecific. This is the first report of SBD after the original description, bringing the total to 14 cases in 5 families. The correct radiological diagnosis and the differential diagnosis, in particular thanatophoric dysplasia, are essential for genetic counselling and obstetrical guidance of families affected with this autosomal recessive dysplasia.