The alkaline phosphatase activity of the peripheral blood neutrophils has been studied extensively during the past 10 years, especially in leukaemia and allied disorders. A deficiency in paroxysmal nocturnal haemoglobinuria (PNH) was noted by Beck and Valentine (1951). This observation has been confirmed and it has been suggested that it is a characteristic feature of the disease (Hartmann and Auditore, 1959; Tanaka, Valentine and Fredricks, 1960; Lewis and Dacie, 1962).
In the present study neutrophil (leucocyte) alkaline phosphatase has been determined in a relatively large number of patients with PNH in order to assess the constancy of the defect and the relationship between the neutrophil alkaline phosphatase activity and the severity of the disease.
PNH is frequently associated with impaired marrow function, manifested by moderate pancytopenia. In a few cases severe, and possibly fatal, marrow failure may occur during the course of PNH. More commonly aplastic anaemia is the dominant feature at the onset while PNH becomes manifest only at a later stage (Dacie and Lewis, 1961). It is convenient to consider this ‘aplastic-PNH’ syndrome separately from typical PNH, although during the PNH phase the disease is no different. Six patients with this syndrome have been studied and the neutrophil alkaline phosphatase results have been compared with those in typical PNH and in aplastic anaemia.