Osteopetrosis is a sclerosing bone dysplasia. Several clinical forms, different by clinical expressions, genetic and biochemical findings, have been reported. There are two major clinical forms of the disease: the autosomal dominant, adult, benign type (incidence has been reported at 1:20.000 births) and the autosomal recessive, infantile malignant type (incidence has been reported at 1:250.000 births). We intend to present a rare case of adult osteopetrosis, we discovered accidentally having radiographs taken for poliarticular pathology.