Idiopathic erythrocytosis as a potential early manifestation with IgA nephropathy: A case report and systematic review.

IgA nephropathy (IgAN) is the most common primary glomerulonephritis, characterized by mesangial IgA immune complex deposition, potentially leading to chronic kidney disease. Idiopathic erythrocytosis, an unexplained elevation of red blood cell mass, has rarely been reported in association with IgAN. We present a systematic literature review and a new case highlighting the temporal relationship between IgAN and idiopathic erythrocytosis. A PubMed search identified four relevant studies detailing IgAN accompanied by unexplained erythrocytosis. The literature suggests an association predominantly observed in male patients, typically concurrent with or subsequent to an IgAN diagnosis. In our case, however, idiopathic erythrocytosis was detected 2 years prior to the onset of clinical signs of IgAN. The patient, initially treated with phlebotomy, presented 2 years later with significant proteinuria, leading to a renal biopsy confirming IgAN. This temporal progression raises the hypothesis that polymeric IgA1 immune complexes may influence erythropoiesis prior to evident renal involvement. Clinicians should consider underlying glomerular disease in patients with unexplained erythrocytosis, even in the absence of overt renal symptoms.