SMOLD is an uncommon, underdiagnosed, and sometimes misdiagnosed breast disease. It typically presents as an erythematous, tender, and often purulent sub- or periareolar mass that may be associated with an areolar sinus and surrounding inflammation. It is also known as subareolar breast abscess and lactiferous or mammary fistulas, and eponymously as Zuska disease.

SMOLD predominantly affects premenopausal women, although cases have also been reported in men. The mean age at diagnosis is approximately 47 years. No pediatric cases have been reported. Although the definitive cause of SMOLD is uncertain, the primary risk factor is a history of smoking, which is noted in up to 90% of cases. Toxins associated with cigarettes and other tobacco products are purported to damage lactiferous ducts by direct injury or localized hypoxia. This damage results in epithelial metaplasia, which gradually progresses to accumulation of keratinocytes, keratin shedding, obstruction of ducts, chronic inflammation, abscess formation, and potentially duct rupture.

SMOLD is also reported to be more common in those with inverted nipples or nipple piercings.