Degenerative changes in the knee after meniscectomy.

and heterophil antibodies is obscure. The material is small, but one might speculate on the possibility that a past cytomegalovirus infection may protect against infections causing heterophil antibodies, and vice versa. Serological tests have been the diagnostic method of the present study. Isolation of virus has not been attempted, but still the diagnosis is well documented. In all cases a significant rise in cytomegalovirus antibody titre was demonstrated in the complement-fixation test and in most cases also in the neutralization test. Proper controls were included in all tests. The Ad. 169 strain of cytomegalovirus was used in the complementfixation test and the neutralization test. The complementfixation test was the primary screening test, and when a sufficient amount of serum was obtained positive serum pairs were subsequently studied in the neutralization test with positive results. If there are antigenically different cytomegalovirus strains, either just one of these has been present here, or there are different strains with the same antigenic substance in common. Quantitative cross-neutralization tests with different cytomegalovirus strains have so far not been made. There is hardly any doubt that the patients reported on have had an infection with cytomegalovirus or with an antigenically related agent. It is impossible to state, however, whether this is a primary acute infection or a disease of secondary reactivated type. The possibility of a complex microbiological cause of the disease with some kind of reactivation of a latent cytomegalovirus infection might thus possibly be discussed in some of the patients presented. In Cases 1 and 10 recurring urinary tract symptoms and in Case 11 repeated episodes of proctitis occurred before the definite onset of the actual disease. Cases 4 and 5 ran clinical courses suggestive of bacterial complications. However, in most of the patients the uniformity of the relation between clinical course and serological response seems to contradict the occurrence of a secondary reactivation of a latent cytomegalovirus infection. Summary