Paroxysmal Nocturnal HemoglobinuriaParoxysmal nocturnal hemoglobinuria, the strangest of this entire group of bizarre diseases, is also the most infrequent. Only 50 cases have been reported since Marchiafava and Nazari60 first recognized the condition as a separate disease entity in 1911. The disease usually appears during the third or fourth decade of life, although it has been described in a child of five and a half years61 and a woman aged fifty-two years.62 Of the reported cases, 25 have been males and 25 females. There is no demonstrable hereditary or familial tendency, and careful studies have failed to reveal predisposing . . .