Lymphadenopathy due to toxoplasmosis.

MANY SEROLOGICAL surveys using the dye test of Sabin and Feldman (1948) have shown infection with Toxoplasma gondii to be widespread. It occurs with various degrees of frequency in different geographic areas and antibodies have been found in man and many species of animals (Feldman and Miller, 1956; Beattie, 1957; Jacobs, Remington and Melton, 1960; Ludlam and Beattie, 1963). As an infection producing clinical symptoms the disease appears to be rare and the best known and longest recognised form in man in the congenital disease to which attention was drawn in 1939 by Wolf, Cowan and Paige. The acquired infection is rarely severe but a manifestation recognised with increasing frequency is lymphadenopathy, which may or may not be associated with mild constitutional symptoms. It is not unusual for the lymphadenopathy to persist for several months and this may raise the suspicion of disease of a more serious nature and result in lymph node biopsy. The histological appearances in the lymph nodes are distinctive, although the specificity of the morphology is at present uncertain (Harrison, 1966). However, Saxen, Saxen and Gronroos (1958), Saxen and Saxen (1959) and Saxen, Saxen and Tenhunen (1962) have reported several series in Finland and stressed the diagnostic significance of the changes, and Tenhunen (1964) wrote that the histology of the lymph nodes established the correct diagnosis in over 90 per cent of cases. The importance of diagnosis lies in the differentiation of toxoplasmic lymphadenitis from malignant reticuloses, especially Hodkin's disease (Saxen et al, 1962) and specific infections. The histology does appear to be uniform and will often allow of a provisional diagnosis which may be confirmed by serological testing for antibodies. The present series of 6 cases has been collected on a histological basis from a routine biopsy service over a fifteen-month period. During this time a total of 340 lymph node biopsies was received giving an incidence of 1.8 per cent. They were drawn from both urban and rural populations in Northern Ireland. The biopsies were undertaken for persistent, unexplained lymphadenopathy and in only one case was toxoplasmosis considered. HISToLOGY The histological changes in all six lymph nodes are very similar, although they vary in degree and the cases have been collected on the basis of the morphology. The lymph nodes are moderately enlarged, but the architecture is preserved. There is a striking degree of follicular hyperplasia and the large follicles with active germinal centres are scattered throughout the node and vary considerably in size. The follicles are well demarcated except where the margins are interrupted by small clusters of histiocytic cells. In the reaction centres there are numerous mitotic figures and macrophages containing nuclear debris are usually abundant. There is often a marked degree of periadenitis associated with fibrous thickening of the