Paroxysmal Nocturnal Hemoglobinuria

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Abstract
Erythrocytes from patients with paroxysmal nocturnal hemoglobinuria are abnormally sensitive to the lytic action of complement and undergo lysis in acidified normal human serum. This lysis was examined as a function of calcium and magnesium ion concentration in eight patients and eight normal donors. The addition of as little as 3 x 10–4 molar magnesium (0.6 mEq per liter) to normal human serum initiated lysis of cells from patients with the disorder, via the alternate pathway of complement activation, and markedly potentiated the lysis of these cells in acidified serum by the same pathway. This finding led to a simple modification of the acidified serum lysis test (Ham test), which renders it more accurate in the diagnosis of paroxysmal nocturnal hemoglobinuria and more precise in delineation of the abnormal erythrocyte populations. Also demonstrated is the fact that calcium ion inhibits lysis of the abnormal cells in acidified and nonacidified human serum. Small changes in the concentration of these cations may result in spontaneous activation of the alternate complement pathway, thereby precipitating hemolytic attacks. (N Engl J Med 289:705–709, 1973)
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