Heterotopic ossification following anti-NMDA receptor encephalitis: a case report

Heterotopic ossification (HO) is defined as the formation of true bone tissue in non-osseous tissues. HO may occur under several conditions such as soft tissue injury, central nervous system injury and many other diseases like arthopathies, and vasculopathies. The underlying mechanisms of HO are not well elucidated. Anti-NMDA receptor encephalitis is a newly recognized autoimmune mediated disease which is predominant in young female patients with ovarian teratomas. Encephalitis complicated with HO has rarely been reported.

Here we report a case of anti-NMDA receptor encephalitis with severe muscle ossifications. A 15 years old female patient presented with fever, changed mental status of confusion, rigidity of the arms and legs, and oral-facial dyskinesias. Diagnosis of anti-NMDA receptor encephalitis was confirmed by detection of anti-NMDA receptor antibodies both in serum and CSF. Due to the severity of the disease, 3-weeks' intensive care and mechanical ventilation were administrated for the patient. Image of pelvic CT and MRI of the patient showed dynamic changing process of HO. The muscles showed edema and scattered inflammation at the very beginning, and then gradually formed mature bone tissue.

Anti-NMDA receptor encephalitis often presents with severe neurologic symptoms and requires long time intensive care and mechanical ventilation, which makes the patient easily complicate with HO. More studies are required to elucidate the mechanisms of HO and more attention should be paid to patients with encephalitis who might develop severe muscle ossifications requiring early interventions.