Overlap Syndrome in a Male Presenting With Progressive Lower Limb Weakness: A Case Report

Overlap syndrome refers to a large group of inflammatory rheumatic conditions characterized by the co-existence of clinical manifestations that include different organ systems and meet the criteria of more than one rheumatic disease. Overlap syndromes are less common compared with the conditions they encompass, for example, the global prevalence of systemic lupus erythematosus (SLE) is estimated to be 43.7 per 100,000 persons, of which only around 3.4-6.3% present with SLE-myositis overlap. Although rare, overlap syndromes commonly include lupus, rheumatoid arthritis, scleroderma, and myositis. Because overlap syndrome can manifest in several ways and has an unpredictable course, it poses a challenge to multidisciplinary teams that examine and treat patients. Therefore, we must not disregard any signs and symptoms as they might have a huge impact on the progression of the disease and the overall outcome of the treatment. We present a rare case of SLE-myositis overlap syndrome in a 44-year-old male. He initially presented with gradual weakness in the proximal muscles of the bilateral lower limb. This patient was diagnosed as having SLE with positive 5g protein/24 hours, anti-nuclear, low C3, anti-U1RNP, anti-Ro, and anti-La antibodies, as well as membranous lupus nephritis evident by the results of renal biopsy. The diagnosis of myositis was also made according to the history and evaluation of the patient, the high titer of muscle enzymes creatine kinase level, and MRI result. Although the patient tested positive for anti-U1RNP, he did not meet the criteria of mixed connective tissue disease. Eventually, the patient was found to have overlap syndrome. The prevalence of overlap between SLE and myositis is relatively rare and varies from 3.4% to 6.3%. To our knowledge, no study has discussed or reported its prevalence among males.