Hypervitaminosis a

an excess of vitamin A, which may lead to skeletal changes.

Acute poisoning with vitamin A does not generally not produce any radiographic abnormalities other than a transient widening of the sutures of the skull from bulging of the fontanelles. Radiographic features of subacute or chronic hypervitaminosis A are virtually confined to children. Usually cortical thickening of the tubular bones occurs in areas in which soft tissue nodules are present; hyperostosis is observed in diaphyses of the ulnae and metatarsal bones and in the clavicles, tibiae and fibulae (Fig.1). Other findings include cupping, shortening, and splaying of the metaphyses, irregularity and narrowing of the cartilaginous growth plates, and hypertrophy and premature fusion of the epiphyseal ossification centres. Also, see chemical agents (III:1), Fig. 4.

Long-term therapeutic use of synthetic forms of vitamin A, such as isotretinoin, may lead to skeletal hyperostosis, arthralgias and myalgias.

Infantile cortical hyperostosis (Caffeys disease) produces skeletal changes that greatly resemble those of hypervitaminosis A.

DR/RB