Age- and joint-specific risk of initial heterotopic ossification in patients who have fibrodysplasia ossificans progressiva.

Using data from a survey of 44 patients who have fibrodysplasia ossificans progressiva, age- and joint-specific risks of new joint involvement were estimated using parametric and nonparametric statistical methods. Regions in which the risk of heterotopic ossification appears to remain constant with age include the neck, spine, shoulders, elbows, and ankles. Regions with apparently increasing risk include the jaw, wrists, hips, and knees. This analysis allows clinicians to estimate the risk of new involvement for any joint at any patient age, as well as the fraction of patients with uninvolved joints at any age. The variation of ossification risk by joint provides a clinically useful guide to the patterns of progression of the disease. Such a guide will help in planning for individual patient needs, as well as anticipating auxiliary social services and rehabilitation programs.

The natural history of heterotopic ossification in patients who have fibrodysplasia ossificans progressiva. A study of forty-four patients.

Forty-four patients who had fibrodysplasia ossificans progressiva responded by mail to a questionnaire regarding the age at the onset of heterotopic ossification at fifteen commonly involved anatomical sites. The average age of the patients when they responded to the questionnaire was twenty-seven years (range, three to sixty-nine years). The average age at the onset of ossification was five years (range, birth to twenty-five years). The most common sites of early heterotopic ossification were the neck, spine, and shoulder girdle. Thirty-five (80 per cent) of the patients had had some restrictive heterotopic ossification by the age of seven years. By the age of fifteen years, forty-two (more than 95 per cent) of the patients had severely restricted mobility of the upper limbs. In these patients, heterotopic ossification proceeded in a direction that was axial to appendicular, cranial to caudad, and proximal to distal; this pattern appeared typical for fibrodysplasia ossificans progressiva.