In 1692, FOP was first described by Guy Patin in a young patient who “turned to wood” .
Myositis ossificans is a very rare disease characterized by heterotopic ossification formation, typically involving muscles, tendons, ligaments, fascia, and aponeurosis. FOP is a rare, hereditary, progressive connective tissue disorder characterized by congenital malformation of the great toes; progressive ossificans occurs mainly in the neck, chest, and back [8, 9].
In our patient’s case, his parents reported that he had had hallux valgus since birth [9, 10]. The initial symptoms of FOP are painful and hard soft tissue swellings over the affected muscles that lead to ossification. It usually occurs from birth to the second decade of life, following spontaneous or trauma-induced flare-ups . Heterotopic ossification usually begins in the cervical paraspinal muscles and later spreads from axial to appendicular, from cranial to caudal, and from proximal to distal sites. Scoliosis is a common finding because of asymmetric heterotopic bones connecting the trunk and pelvis . Fusion of ossicles of the ear leads to conductive hearing loss, which is a common feature associated with this condition [6, 13, 14]. Progressive episodes of heterotopic ossification lead to ankylosis of all major joints of the axial and appendicular skeleton, rendering movement impossible. In the second decade of life, mostly patients with FOP are confined to bed or wheelchair [6, 15]. The most common cause of death in FOP is cardiopulmonary failure resulting from thoracic insufficiency syndrome .
FOP diagnosis is clinical, and it is usually made on the basis of the presence of three major criteria [6, 14]: congenital malformation of the great toes, progressive heterotopic endochondral ossification, and progression of the disease in well-defined anatomical and temporal patterns. Laboratory tests may show a discreet increase of the erythrocyte sedimentation rate during the flare-ups. Genetic analysis for ACVR1 gene mutation is a confirmatory test. Imaging examinations such as radiography and computed tomography show the heterotopic bones and are useful to confirm the diagnosis.
FOP should be differentiated from other similar conditions, including progressive osseous heteroplasia, Albright hereditary osteodystrophy, osteoma cutis, ankylosing spondylitis, Still disease, Klippel-Feil-syndrome, brachydactyly, juvenile bunions, sarcoma, and desmoid tumor [9, 14].
Treatment of FOP is administered using a multidisciplinary approach based on injury prevention, conservative use of analgesics, and surgery.
Surgical excision is considered when excessive pain, joint limitation, or nerve compression is present. Surgery generally is advised when myositis ossificans is ripe, identified by a higher bone density in x-ray findings and normal erythrocyte sedimentation rate and alkaline phosphatase level.
Physical rehabilitation should be focused on enhancing activities of daily living through approaches that avoid passive range of motion that could lead to disease flare-ups [6, 8]. Flare-ups of FOP may occur spontaneously or be precipitated by trauma, such as intramuscular injections, including vaccines and muscle biopsy. Moreover, in routine dental care, overstretching of the jaw and intramuscular local anesthetic injections also should be avoided. Patients with FOP may have an additional risk of flare-ups after influenza-like illness. Thus, a subcutaneous influenza vaccine could help these patients, particularly those who have severe restrictive disease of the chest wall and are at a greater risk of presenting with complications of respiratory infections, which are a frequent cause of death [6, 11]. Drug treatment of our patient was based on the current treatment guidelines published by Kaplan et al. . Corticosteroids are advised as the first line of treatment at the beginning of flare-ups. The use of corticosteroids should be restricted to treatment of flare-ups that affect major joints, the jaw, or the submandibular area. Corticosteroids should not be used for symptomatic treatment of flare-ups that involve the back, neck, or trunk, owing to the long duration and recurring nature of these flare-ups and the difficulty in assessing the true onset of such flare-ups . When prednisone is discontinued, a nonsteroidal anti-inflammatory drug or a Cox-2 inhibitor (in conjunction with a leukotriene inhibitor) may be used symptomatically for the duration of the flare-up . None of these drugs avoided the progression of the disease in our patient.