A mild autosomal recessive form of osteopetrosis.

We report on four individuals in one kindred with relative or absolute short stature; increased upper/lower segment ratio with decreased arm span; mandibular prognathism and dental abnormalities; fractures following minimal trauma; mild to moderate anemia with extramedullary hematopoiesis; and radiographic changes of osteopetrosis, including sclerosis of the cranial base, generally increased bone density, sclerosis of the vertebral end plates, and transverse bands and poor diaphyseal modelling of the long bones. There is intrafamilial variability of clinical and radiographic findings in individuals with this mild, autosomal recessive form of osteopetrosis. We summarize ten families from the literature, which include 18 cases of mild recessive osteopetrosis. The manifestations of many are similar to those of the individuals reported here. Two other types of recessive osteopetrosis have been reported previously: osteopetrosis associated with renal tubular acidosis, and severe osteopetrosis with hepatosplenomegaly, pancytopenia, and early death. Autosomal dominant osteopetrosis is variable but usually mild. Pedigree analysis is currently the only reliable method of determining the pattern of inheritance in mild osteopetrosis.