An unusual case of extra bone formation

S. M. Carty, J. Yoong1, T. M. Lawson1 and M. J. Bevan1

Rheumatology, University of Wales College of Medicine, Cardiff and 1 Rheumatology, Princess of Wales Hospital, Bridgend, UK

Correspondence to: S. M. Carty. E-mail: Cartysm{at}cf.ac.uk

The patient, a 40-yr-old female with fibrodysplasia ossificans progressiva, first presented in her teens with pain and stiffness of her arms. Her symptoms progressed to involve her legs and axial skeleton and she became wheelchair-bound at the age of 40. Her condition continues to deteriorate.

The clinical features are of progressive ossification, which starts distally and affects axial muscles, ligaments, fascia, tendons and joint capsules (Fig. 1). Symmetrical digital abnormalities are present at birth and normally precede the soft-tissue ossification. The most common abnormality is hallux valgus with microdactyly of the first toes, with hypoplasia or synostosis of the phalanges. In some cases similar abnormalities are found in the fingers (Fig. 2).
FIG. 1.

FIG. 2.

A variety of treatments, including corticosteroid and bisphosphonates, have been used but none has been shown to slow disease progression.

It is a rare autosomal dominant condition (1 per 2 million) with variable phenotypic expression but complete penetrance. The gene responsible is found on chromosome 4q27-31 but no mutation has been identified. Although the exact mechanism remains unclear, there is overexpression of bone morphogenetic protein type 4 in circulating lymphocytes and in all cell types in the affected areas.





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