Ribbing (1949) described a family with a disorder he designated hereditary multiple diaphyseal sclerosis. According to Seeger et al. (1996), only 13 cases of Ribbing disease had been previously described in the English literature; these were reported by ... Ribbing (1949) described a family with a disorder he designated hereditary multiple diaphyseal sclerosis. According to Seeger et al. (1996), only 13 cases of Ribbing disease had been previously described in the English literature; these were reported by Paul (1953), Shier et al. (1987), and Furia and Schwartz (1990). Ten of these cases were sibs from 3 different families; the other 3 were unrelated. In 8 cases, both tibias were involved only. Five cases involved, respectively, the tibia unilaterally; bilateral tibias and unilateral femur; bilateral tibias and unilateral fibula; bilateral femurs and unilateral tibia; and bilateral tibias, unilateral femur, and radius. Of these 13 patients, 7 presented with pain and 3 with swelling followed by pain. Lesions in the 3 asymptomatic patients were discovered during evaluation of asymptomatic sibs. The distinction between Ribbing disease and Camurati-Engelmann disease (progressive diaphyseal dysplasia; 131300) has been unclear. Engelmann disease has been more frequently reported. It is a progressive disorder associated with pain, muscle weakness, fatigue, waddling gait, and anemia. Though Engelmann disease and Ribbing disease may appear to be identical radiographically, Seeger et al. (1996) pointed to clinical and histologic differences. Whereas Engelmann disease presents during childhood, Ribbing disease usually presents later in life; Seeger et al. (1996) wrote that 'patients contract Ribbing disease after puberty.' Engelmann disease is bilateral and symmetric, whereas Ribbing disease is either unilateral or asymmetrically and asynchronously bilateral. Engelmann disease affects long bones and bones formed by intramembranous ossifications; therefore, the skull is involved almost as frequently as the long bones. Ribbing disease has been reported only in the long bones. Whereas Engelmann disease features trabecular thickening, normal or enlarged haversian systems, and both osteoblastic and osteoclastic activity, implying bone formation and resorption, histologic study in Ribbing disease shows osteoblastic activity alone and progressive obstruction of the haversian systems. Finally, Seeger et al. (1996) noted that there may be a difference in mode of inheritance. Engelmann disease is autosomal dominant, with considerable variation in penetrance. In the 4 sibs of both sexes affected in a single generation in the family studied by Ribbing (1949), and in other Ribbing disease families as well, autosomal recessive inheritance appears to be demonstrated. On imaging studies, Ribbing disease may simulate a stress fracture, chronic infection, bone-forming neoplasia, or a systemic metabolic or endocrine disorder. Makita et al. (2000) reported a 3-generation Japanese family with Engelmann disease with a wide variation in phenotype among the affected family members. Of the 12 patients, 7 had full manifestations of Engelmann disease, while the other 5 exhibited only segmental (rhizomelic and/or mesomelic) involvement and asymmetric diaphyseal sclerosis without any clinical symptoms, resembling Ribbing disease. The authors proposed that Engelmann disease and Ribbing disease represent phenotypic variation of the same disorder.