Metaphyseal dysplasia (also known as Pyle disease, metaphyseal chondrodysplasia, metaphyseal dysostosis) is a rare autosomal recessive disorder characterized by flaring of the ends of long bones with relative constriction and sclerosis of the diaphysis and mild cranial sclerosis. It is one of the causes of an Erlenmeyer flask deformity. The flared metaphyses are relatively lucent.
The patients are often asymptomatic although genu valgus deformity may be a feature.
Where there is cranial involvement, it is termed craniometaphyseal dysplasia.