Late-onset progressive facial hemiatrophy (Parry-Romberg syndrome).

Initially described by Parry in 1825 and systematized by Romberg in 1846, progressive facial hemiatrophy syndrome is a controversial and poorly understood entity, with sporadic occurrence and no known mendelian inheritance. It is a slowly progressive disorder, affecting chiefly females in their first and second decades of life, characterized by unilateral atrophy of facial tissues, mostly skin and subcutaneous fat and, in a lesser degree, muscles and bones. It is closely associated with linear scleroderma en coup de sabre. However, both conditions may be overlapping and there may be evolution from one process into another. Its origin is unknown, and several hypotheses have been proposed (encephalitis, trauma, scleroderma, migraine, infection, vasculitis, genetic factors, malformative hypothesis), but a multifactorial pathogenesis may be most likely. Protean multi-systemic manifestations have been described, including ocular involvement, ear, nose and throat disorders and neurological findings.