Cytomegalovirus colitis and immunotherapy

Toxic megacolon: remember cytomegalovirus

A 63-year-old female retired clerical officer was admitted with a 1-week history of profuse diarrhoea. The patient had been diagnosed with non-Hodgkin's lymphoma 4 years previously, and a human immunodeficiency virus (HIV) test at that time was negative. She had received two regimens of chemotherapy, and had been in remission for 3 months with a normal leukocyte count. The diarrhoea was watery with no blood or mucus, and associated with mild nausea and diffuse left-sided abdominal pain relieved by defaecation. The patient had a mild pyrexia and scanty bowel sounds, but the abdomen was not distended. Full blood count and full biochemistry were normal apart from the white cell count (13.8x109/litre — predominantly neutrophils and monocytes). Initial blood cultures and routine viral serology were negative, but the latter was never repeated. Stool samples were negative for bacteria, parasites and toxins.

The molecular basis of intractable diarrhoea of infancy

The intractable diarrhoeas of infancy present very major problems of clinical management. However, the conceptual importance of these conditions lies in the information that they may provide about normal small-intestinal function in humans: among such infants will be found the human equivalents of the 'knock-out' mice, in which targeted gene disruption allows sometimes unexpected insight into the regulation of intestinal function. The challenge posed by the intractable diarrhoeal syndromes, of working backwards from an apparently common phenotype to probably multiple genotypes, is, however, immense. Very few of these conditions have been described at the genetic level, although the molecular basis of pathogenesis has been better explored in recent years. The two major groups of intractable diarrhoea are due to (1) primary epithelial abnormalities (which usually present within the first few days of life) and (2) immunologically mediated (which generally present after the first few weeks). The high prevalence of autoimmune enteropathy among infantile autoimmune disease, in contrast to adult autoimmunity, is intriguing and may reflect constitutive abnormality of extrathymic lymphocyte maturation. The use of potent immunosuppressive drugs and increasing expertise with parenteral nutrition are improving the outlook of these previously fatal conditions. Viewed globally, however, the pressing problem is to treat effectively the millions of infants who die from severe persistent diarrhoea and wasting, which would certainly not be considered intractable in wealthy countries.