A unique presentation of a rare disease: biopsy proven systemic lupus erythematosus and microscopic polyangitis: an overlap syndrome.

Systemic Lupus Erythematosus (SLE) and ANCA-associated vasculitis are classically thought to be separate diseases with different pathophysiologies. An overlap of these diseases has been reported few times in the literature. We present a unique case of a Caucasian male in his third decade of life, without a previous personal or family history of autoimmune disease, with serological and biopsy findings of both diseases occurring simultaneously. ANCA, typically p-ANCA, can be detected in up to 30% of SLE patients and can be higher with renal involvement. Patients with overlap syndrome have increased complications and higher mortality rates than those with either disease alone. Our patient was found to have necrotizing and crescentic glomerulonephritis, most consistent with ANCA vasculitis, specifically microscopic polyangitis with MPO positive staining. The biopsy also revealed abundant immune-complex deposits consistent with WHO class V diffuse membranous lupus glomerulonephritis. These diseases are typically seen in young to middle aged females, and given the rarity of this case, biopsy findings were confirmed by two pathologists from separate institutions. Presentations of autoimmune diseases and vasculitis can be multi-systemic. Immediate action and appropriate work up with a multidisciplinary team is required for optimal patient care. Our patient displayed pulmonary-renal involvement in addition to systemic features such as fevers, myalgia and profound anemia. Considering overlap syndromes, especially in patients with underlying connective tissue disease or systemic vasculitis, is vital for the prevention of excess morbidity in this population.