Autosomal dominant endosteal hyperostosis is a generalized bone dysplasia characterized by a cortical thickening of the long bones, with no alteration in external shape, and a remarkable resistance of the bone to fracture. The skeleton is normal in childhood. Facial metamorphoses occur in adolescence, as the forehead flattens, the mandible becomes elongated, and the gonial angle decreases. An enlarging osseous prominence (torus palatinus) develops in the hard palate, which may lead to malocclusion or loss of teeth (summary by Van Wesenbeeck et al., 2003).

Camurati-Engelmann Disease not associated with TGFB1. This is an n-of-1 use case where only one patient or family has been described with this disorder.

Melorheostosis (MEL) is characterized by 'flowing' hyperostosis of the cortex of tubular bones. The lesions are usually asymmetric and involve only 1 limb or correspond to a particular sclerotome. They may be accompanied by abnormalities of adjacent soft tissue, including joint contractures, sclerodermatous skin lesions, muscle atrophy, or hemangiomas (review by Hellemans et al., 2004). The designation combines root words meaning 'limb,' 'flow,' and 'bone.' Melorheostosis may sometimes be a feature of Buschke-Ollendorff syndrome (BOS; 166700), a benign disorder which is caused by mutation in the LEMD3 gene (607844). Although germline or somatic LEMD3 mutations had been postulated to cause isolated melorheostosis (Butkus et al., 1997; Debeer et al., 2003; Happle, 2004; Hellemans et al., 2004), several studies have not been able to prove this (Hellemans et al., 2004; Mumm et al., 2007; Zhang et al., 2009).

PHOAR2-enteropathy syndrome (PHOAR2E) is characterized by primary hypertrophic osteoarthropathy (PHO) and/or chronic nonspecific ulcers (CNSU) of the small intestine. The cardinal features of PHO are digital clubbing, pachydermia, and periostosis; other manifestations include swelling and pain of the large joints, hyperhidrosis, seborrhea, and acne. CNSU often presents with chronic unexplained anemia and abdominal pain, and patients may exhibit edema due to hypoalbuminemia. Radiologic imaging or endoscopy shows multiple small ulcers, predominantly in the ileum, although the stomach, duodenum, and jejunum are often involved. PHO is more frequent and more severe in male patients, who often also report watery diarrhea, whereas CNSU is more often diagnosed in female patients, who may also show features of PHO such as digital clubbing or arthralgias and swelling of the joints. The same mutations in the SLCO2A1 gene have been reported in patients presenting with either diagnosis, and presumed sex-related modifiers of the manifestations of disease or other genotype/phenotype correlates have yet to be elucidated (Li et al., 2017; Umeno et al., 2018; Hong et al., 2022; Kimball et al., 2024). For a discussion of genetic heterogeneity of PHO, see PHOAR1 (259100).

Hyperphosphatemic familial tumoral calcinosis (HFTC) is characterized by: Ectopic calcifications (tumoral calcinosis) typically found in periarticular soft tissues exposed to repetitive trauma or prolonged pressure (e.g., hips, elbows, and shoulders); and Painful swellings (referred to as hyperostosis) in the areas overlying the diaphyses of the tibiae (and less often the ulna, metacarpal bones, and radius). The dental phenotype unique to HFTC includes enamel hypoplasia, short and bulbous roots, obliteration of pulp chambers and canals, and pulp stones. Less common are large and small vessel calcifications that are often asymptomatic incidental findings on radiologic studies but can also cause peripheral vascular insufficiency (e.g., pain, cold extremities, and decreased peripheral pulses). Less frequently reported findings include testicular microlithiasis and angioid streaks of the retina.