The presented case-history demonstrates an infant with a rare bone disease with a very serious prognosis. Based on X-ray findings on the skeleton (sclerosis of the diaphyses of long bones, ribs, vertebrae and in particular the base and vault of the skull), the diagnosis of morbus Camurati-Engelmann--progressive diaphyseal dysplasia was established. With regard to the striking progression of the process in the cranial area and the progressing stigmatization of the patient's face, the authors consider also a more recent diagnostic unit--craniodiaphyseal dysplazia. With advancing sclerotization of the skull the most serious complications are compression of the cranial nerves which can be resolved in the final stage only by surgery. From a brief review of the literature: the aetiology of the disease is not known, the therapeutic effect of prednisone or calcitonin is small.