Forty two infants below the age of 2 years presenting with chronic non-infective diarrhoea and shown to have histologically proved colitis were investigated over a five year period. Allergic colitis was the most common cause of colitis, accounting for 62% of the cases. Other colitides diagnosed included: non-specific colitis, autoimmune enterocolitis, and ulcerative colitis accounting for 10% each; severe combined immunodeficiency 7%, and Crohn's disease 3%. A positive family history and a personal history of atopy were obtained in 48% and 29% of the cases respectively. Serum immunoglobulin A, IgG₂, and IgG₄ were very low in over 50% of the entire cohort of infants with colitis; 66% of those with severe combined immunodeficiency, autoimmune enterocolitis, and ulcerative colitis (n = 11) had low CD3 and CD4 T lymphocytes with an accompanying increase in CD8 in two thirds of those with severe combined immunodeficiency. T lymphocytes were normal in those with allergic colitis. Thus infants with proved non-infective colitis as a group show a high prevalence of IgA, IgG₂, and IgG₄ deficiency. It is likely that this minor deficiency of mucosa associated immunoglobulin production has a role in the pathogenesis of the colitic process.

Keywords: infants; rectal bleeding; colitis; serum immunoglobulin A; immunoglobulin G subclasses