The kidney in paroxysmal nocturnal haemoglobinuria: MRI findings.

Paroxysmal nocturnal haemoglobinuria (PNH) is a rare, acquired stem-cell disorder characterized by defective haematopoiesis, which results in an increased sensitivity of the erythrocytes to complement-mediated intravascular haemolysis. Renal damage is infrequent but can produce chronic renal failure due cortical deposits of haemosiderin and microvascular thrombosis. MRI provides characteristic images of the kidneys that enable haemosiderin deposition to be diagnosed; in PNH, MRI typically shows reversed renal cortex-medulla differentiation on T(1) weighted images and substantial loss of cortical signal intensity on both T(1) and T(2) weighted images. We describe the MRI findings of renal cortical haemosiderosis occurring in four patients with PNH.