Scalp nodules as a presenting sign of fibrodysplasia ossificans progressiva: a register-based study.

BACKGROUND: Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder characterized by progressive ossification of soft tissues. Clinical diagnosis is important because trauma from lesional biopsies can exacerbate the disease. OBJECTIVE: We sought to evaluate the frequency of scalp nodules as the presenting manifestation of FOP. METHODS: We describe 3 infants with FOP who presented with multiple neonatal scalp nodules. We reviewed all 43 cases of this disorder in the French FOP registry. RESULTS: Scalp nodules were found in 40% of cases and usually represented the first manifestation of the disease. All 43 patients had characteristic skeletal malformations involving the great toes (n = 43), fingers (n = 12), and vertebrae (n = 3). Other abnormalities were cerebral malformations (n = 1) and alopecia (n = 2). Histopathologic analysis did not contribute to the differential diagnosis and was interpreted as cranial fasciitis in two patients. LIMITATIONS: Our study was retrospective, and the presence or absence of scalp nodules was not always recorded. CONCLUSION: Neonatal scalp nodules associated with a characteristic malformation of the great toes are a common presentation of FOP. Physicians should be aware that lesional biopsies can exacerbate the disease and must therefore be avoided. A diagnosis of classic FOP can be confirmed by molecular genetic studies.