An overview of mastitis and breast abscess in infants, children, and nonlactating adolescents will be presented below. Breast infections in lactating women and adults are discussed separately. (See "Lactational mastitis" and "Breast abscess".)
EPIDEMIOLOGY AND PREDISPOSING FACTORS
Breast infection (mastitis or breast abscess) typically occurs in infants younger than two months of age (infant mastitis) and lactating women [1-6].
During the first two weeks of age, neonatal mastitis occurs with equal frequency in girls and boys [2,3]. Thereafter, it is more common in girls, with a female:male ratio of approximately 2:1 . This is thought to be related to the longer duration of physiologic breast hypertrophy in female than in male infants . Maternal skin or soft-tissue infection in the postpartum period may be associated with neonatal mastitis [7-9]. Manipulation of the infant breast to express a clear or cloudy (milk-like) nipple discharge ("witch's milk") has been considered to be a risk factor for breast abscess, but this finding is not well substantiated .
Although it is less common than in infants, breast infection also may occur in prepubertal children and pubertal/postpubertal adolescents [1,6,10]. Factors that predispose to breast infection in children and nonlactating adolescents include trauma (eg, breast manipulation during sexual activity, shaving or plucking periareolar hair, nipple piercing), obesity, mammary duct ectasia, local skin infection, and epidermoid cysts [6,10-13]. Peripheral mastitis may be associated with diabetes mellitus, rheumatoid arthritis, glucocorticoid therapy, granulomatous disease, and trauma .
Infant mastitis — The vast majority of cases of infant mastitis are caused by Staphylococcus aureus [1-5,14,15]. Less common causes include gram-negative enteric organisms (eg, Escherichia coli, Salmonella), anaerobes, and group B streptococcus (S. agalactiae) [1,4,14-19].