A Rare Case of Mixed Connective Tissue Disease (MCTD) with Intricate Features of Lupus, Polymyositis and Rheumatoid Arthritis Presenting with Severe Myositis

Mixed connective tissue disease (MCTD) includes clinical and laboratorial manifestations of systemic lupus erythematosus, scleroderma and polymyositis along with high titres of anti-U1RNP antibodies. In the initial phases of the disease, muscle enzyme levels increase but the disease remains generally subclinical. Presentation with myositis is uncommon. Our objective is to report a rare case of a patient who presented with a severe onset of myositis characterized by dysphagia, an increase in myopathy and joint involvement suggestive of RA. The patient was initiated on pulse corticosteroid therapy along with methotrexate in view of her elevated Creatine Kinase levels and biopsy findings that were suggestive of severe myositis. The patient showed clinical and laboratory improvement with this regimen. Though severe myositis and arthritis can occur in overlap syndrome, MCTD evolved as a separate disease entity due to presence of high titres of Anti U1-RNP antibodies. The authors emphasize that this is an extremely rare presentation of MCTD with only two previous cases seen in literature, one of a 13 year old child and the other being an adult female both of whom had evidence of myositis on presentation.