Hemoglobinuria Misidentified as Hematuria: Review of Discolored Urine and Paroxysmal Nocturnal Hemoglobinuria

Discolored urine is a common reason for office visits to a primary care physician and urology referral. Early differentiation of the type or cause of discolored urine is necessary for accurate diagnosis and prompt management. Paroxysmal nocturnal hemoglobinuria is a clonal disorder caused by acquired somatic mutations in the PIG-A gene on the X- chromosome of hemopoietic stem cells and leads to deficiency of surface membrane anchor proteins. The deficiency of these proteins leads to an increased risk of hemolysis of erythrocytes and structural damage of platelets, resulting in a clinical syndrome characterized by complement-mediated intravascular hemolytic anemia, bone marrow failure, and venous thrombosis. Patients with this clinical syndrome present with paroxysms of hemolysis, causing hemoglobinuria manifesting as discolored urine. This can be easily confused with other common causes of discolored urine and result in extensive urologic work-up. Three commonly confused entities of discolored urine include hematuria, hemoglobinuria, and myoglobinuria. Specific characteristics in a dipstick test or urinalysis can guide differentiation of these three causes of discolored urine. This article begins with a case summary of a woman presenting with cranberry-colored urine and a final delayed diagnosis of paryxysmal nocturnal hemoglobinuria. Her hemoglobinuria was misdiagnosed as hematuria, leading to extensive urologic work-up. The article also gives an overview of the approach to diagnosing and treating discolored urine.