Association of idiopathic inflammatory myopathy and Crohn's disease

We describe a rare case of concurrent polymyositis and Crohn's disease in a female patient. A 69-year-old female presented in December 2007 with a 5-month history of proximal muscle weakness, pain, fatigue and difficulty in walking and swallowing. Blood tests revealed elevated creatine kinase (3,429 U/l) and lactate dehydrogenase (2,013 U/l) levels. Magnetic resonance imaging found lumbar disc protrusion. Review by immunologists showed a diagnosis of idiopathic inflammatory myopathy. Though electromyography and muscle biopsy at this point were non-specific, corticosteroid treatment was commenced. Her condition worsened precipitously leading to hospitalisation under immunologists. As the provisional diagnosis was polymyositis, we commenced 1.5 mg/kg per day corticosteroid but her muscle power did not improve. Recurrent abdominal symptoms lead to ultrasonography showing intestinal inflammation. While tumour markers were elevated, thorough investigation failed to identify a tumour. Corticosteroid therapy was continued. Persistent abdominal symptoms lead to repeat colonoscopy and biopsy confirming Crohn's disease. Repeat electromyography and muscle biopsy confirmed the diagnosis of polymyositis. Her corticosteroids were tapered off and 5-aminosalicylic acid and azathioprine were started. Her myositic symptoms gradually abated with improvement in her Crohn's disease. She is now able to walk independently and takes 8 mg/day corticosteroids and her muscle enzyme levels are normal. Remember rare systemic associations when dealing with immune-mediated disease. Consider myositis in the differential diagnosis of Crohn's disease associated myopathy. Treating Crohn's disease may lead to improvement in steroid-resistant myositis where the two are associated.