An inherited disorder characterized by disseminated connective tissue nevi and osteopoikilosis.
Curth Syndrome; Schreus Syndrome; Disseminated Dermatofibrosis with Osteopoikilosis; Dermato-Osteopoikilosis; Dermatofibrosis Lenticularis Disseminata with Osteopoikilosis; Osteopathia Condensans Disseminata.
Named after Abraham Buschke (1868-1943), a German dermatologist and Helen Ollendorff Curth (born 1899), a German-American dermatologist, who first described the disorder in 1928.
Approximately 1:20,000 live births with both genders equally affected.
Autosomal dominant with incomplete penetrance. Disease expression is highly variable, sometimes even within affected families. The vast majority of affected patients have a family history of BOS. It is caused by loss-of-function mutations in the LEMD3 (LEM domain-containing protein 3) gene, which has been mapped to chromosome 12q14.3 and encodes the inner nuclear membrane protein MAN1. Its mutations can cause osteopoikilosis (and melorheostosis) by antagonizing signaling from transforming growth factor β (TGF-β) and bone morphogenetic proteins (BMP).
Based on the characteristic, slightly yellowish papules, and nodules distributed symmetrically or asymmetrically on the trunk and extremities with induration of the skin and subcutaneous tissues. These skin changes are also called dermatofibrosis lenticularis disseminata. Radiographs show circumscribed sclerotic areas near the epiphyses and metaphyses of the bones, particularly of the pelvis and extremities.
The skin lesions typically appear during childhood, are most often asymmetrical on the lower back, buttocks and legs and consist of elastic or collagenous nevi and less frequently of elastomas, collagenomas or dermatofibrosis lenticularis disseminata. These skin lesions may either resolve with age or increase in size and number and often coalesce into one or more larger, yellow, white or skin-colored plaques. Skin lesions may be the only finding, but far more often occur in combination with several different osseous anomalies, of which osteopoikilosis (OPK) is the most common form that usually presents during puberty as asymptomatic dense “bony islands.” Radiologically, OPK appears as multiple, small, well-demarcated, symmetric, round to spindle-shaped sclerotic, radiodense lesions typically affecting the epi- and metaphyses of the long tubular bones, hands, and feet. Histopathologically these lesions correspond to lamellar osseous tissue with Haversian systems. Melorheostosis, a cortical hyperostotic and often painful anomaly that is characterized by radiolucent “dripping wax” appearance in the cortex of the long bones is far less frequently encountered (in 5% of patients) and can occur together with OPK. Other findings may include diabetes mellitus (in 6% of patients), short stature (in 5%), spinal canal stenosis (associated with OPK) and hearing loss (each in 2%; due to condensation of the petrous bone associated with OPK or otosclerosis), cleft-lip palate and rarely aortic stenosis. Some degree of developmental delay or attention-deficit-hyperreactivity disorder (ADHD) has been reported in approximately 5% of patients.