REVIEW The challenge of mastitis

The process of lactation and feeding, referred to by some as the final stage of labour is remarkably successful. This phase of infant care has been subjected to considerable evolutionary pressure since the earliest mammals, reptiles and birds diversified. It has allowed thousands of species to occupy a vast range of ecological niches. Yet a significant complication of breast feeding remains inflammation of the lactating tissue: the pathology of mastitis. Mastitis rarely develops outside lactation, although it may affect individuals at any age in relation to congenital lesions such as duct ectasia, chronic disseminated infections such as tuberculosis, or during granulomatous, autoimmune or malignant processes. The immunology and consequences of mastitis as well as its impact on vertical transmission of infection require careful examination. Mastitis in the lactating mother is impor-tant for paediatricians for two mainreasons. Firstly, it is a major cause of reduction inmilk production and approximately a quarter of mothers cite mastitis as their reason for stopping breast feeding.1 Secondly, by altering the cellular composition of milk and local defences within the breast itself, mastitis is a powerful risk factor promoting vertical transmission of infections.2 The conditionmay go on to give rise to a local abscess. The diagnosis of mastitis is usually clinical, based on breast tenderness, signs of local inflam-mation, and a reduction in milk output. Parallels tend to be drawn with various domesticated ani-mals, in which by contrast diagnosis rests on quantitative measures, the most common of which is an increased milk cell count.3 Estimates of this are widely employed to assess agricultural milk quality with lower counts attracting higher milk prices. Other objective methods have in-cluded estimates of electrical conductivity and measures of specific enzymes or inflammatory mediators within milk (table 1).