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Chin-on-chest deformity in patients with fibrodysplasia ossificans progressiva. A case series.

Fibrodysplasia ossificans progressiva is a rare and disabling autosomal dominant disorder of joint malformations and progressive heterotopic ossification1-4 caused by a recurrent missense point mutation in activin receptor IA (ACVR1, also called ALK2), a bone morphogenetic protein (BMP) type-I receptor2,3,5. Joints become permanently ankylosed in positions that drastically impair activities of daily living and even life itself6. Progressive heterotopic ossification usually begins in the first decade of life, typically appearing first in the dorsal, axial, cranial, and proximal regions of the body, and then later in the ventral, appendicular, caudal, and distal regions1-4,7. Lesions are characterized by the rapid appearance of painful, highly vascular fibroproliferative swellings that progress through an endochondral process to form mature ossicles of heterotopic bone3,8. Lesions may develop spontaneously, although falls9, soft-tissue injury2,3,10, mandibular blocks11, intramuscular immunizations12, viral illnesses13, and surgical trauma10 can precipitate new flare-ups resulting in heterotopic ossification.

Although the classic clinical features of fibrodysplasia ossificans progressiva have been well described, manifestations of the disease affecting the cervical spine are less well known. Neck stiffness is an early finding in most patients and can precede the onset of heterotopic ossification2,4,10. Characteristic malformations of the cervical spine include large posterior elements; tall, narrow vertebral bodies; and fusion of the facet joints from C2 to C72,14,15. In the present report, we describe a rare, but potentially life-threatening, chin-on-chest deformity that may develop in patients with fibrodysplasia ossificans progressiva and a surgical strategy that has been effective for achieving substantial correction of the deformity. The families were informed that …