MRI scans of the kidneys of an 83-year-old woman with history of myelodysplastic syndrome are shown (A and B). Normal MRI scans are shown for comparison (C and D). The patient had intermittent episodes of dark-colored urine for years. Findings from repeated cystoscopies were normal.
Review of her urine studies from several recent hospitalizations revealed blood on dipstick with few or absent red blood cells per high-power field on microscopic examination, consistent with hemoglobinuria. Further studies revealed an elevated reticulocyte count and lactate dehydrogenase level, low levels of haptoglobulin and iron, normal 24-hour urine protein and complement levels, a negative Coombs test result, a leukocyte alkaline phosphatase score of zero (normal range, 11 to 95), and a positive sucrose lysis test result. These findings suggested the diagnosis of paroxysmal nocturnal hemoglobinuria (PNH). Flow cytometry showed a loss of CD55 and CD59 from the granulocytes, which confirmed the diagnosis (to rule out paroxysmal nocturnal hemoglobinuria, both CD55 and CD59 expression must be greater than 90%).
The patient's MRI scans showed diminished T1- and T2-weighted signal intensity in the cortex of both kidneys, consistent with iron deposition. No evidence of renal masses was found. MRI scans of the liver, spleen, and pancreas showed normal signal intensity.
PNH is a chronic disorder. Chronic filtration of hemoglobin through the kidneys results in hemosiderin deposits in the cells of proximal tubules in the renal cortex. T1- and T2-weighted MRI scans of the kidneys show decreased signal intensity in the renal cortex compared with the renal medulla.
The treatment of PNH consists mainly of supportive care with frequent blood transfusions to correct iron deficiency anemia. The roles of androgens, glucocorticoids, and monoclonal antibodies have been studied in reducing the risk and frequency of hemolysis.