Rheumatoid myositis leading to acute lower extremity compartment syndrome: a case-based review.

Muscle pain and weakness in a rheumatoid arthritis (RA) patient has a broad differential, and myositis should be considered early in the disease course as serious limb and life-threatening sequelae may occur. A 55-year-old woman with a past medical history of methotrexate-controlled RA presented with right leg pain for 4 days. The patient suffered sensory loss in the right foot and decreased strength in the toes. Lab tests revealed elevated creatine kinase, ESR, and anti-rheumatoid factor antibody titers. CT scan revealed myositis of posterior compartment muscles. Progressive edema, pain, and neuromuscular deficits persisted despite steroid and antibiotic therapy, so the patient was taken for urgent fasciotomy for acute compartment syndrome. The muscle biopsy showed diffuse mononuclear cell infiltration as well as perivascular and perineural involvement consistent with rheumatoid myositis (RM). The patient did well post-op on a prednisone taper. This case underlines the systemic nature of RA and exemplifies the severity of inflammation that may lead to grave consequences such as compartment syndrome. The histopathology is diagnostic when there is evidence of mononuclear cell infiltration; however, this is not entirely specific. Early, aggressive therapy with immunosuppressives is warranted in such patients. RM has not, to our knowledge, been recorded to cause acute compartment syndrome. Clinicians should be aware of this uncommon manifestation of RA keeping the various presentations of rheumatoid disease in mind when faced with these patients.