Leukaemoid reactions in disseminated tuberculosis.

Secondary haematological changes in tuberculosis may mimic many blood dyscrasias, including leukaemia. The appearance of primitive white cells in the peripheral blood is probably more common in disseminated than in pulmonary tuberculosis (Muller, 1943; O'Brien, 1954). The reaction may involve any cell type: myeloid reactions have been reported by Marzullo and deVeer (1931) and Custer and Crocker (1932), lymphatic reactions by Gardner and Mettier (1949) and Staffurth and Spencer (1950), and a monocytic reaction by Gibson (1946). The term "leukaemoid reaction" was introduced by Krumbhaar (1926) to describe blood changes " indistinguishable from one of the various forms of leukaemia." In many cases a leukaemoid reaction can be distinguished from leukaemia by considering the clinical and laboratory findings. In some, especially those in which the leukaemoid reaction is secondary to disseminated tuberculosis, diagnosis is difficult or impossible and the true nature of the haematological changes is recognized only at postmortem examination. The two following cases presented with haematological changes suggestive of myeloid leukaemia. Disseminated " non-reactive " tuberculosis, characterized histologically by widespread foci of severe necrosis containing many tubercle bacilli and with little or no peripheral cellular response, was found at post-mortem examination.