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.