Idiopathic granulomatous mastitis in Hispanic women - Indiana, 2006-2008.

Idiopathic granulomatous mastitis (IGM) is a rare inflammatory breast lesion of unknown etiology that occurs in women of childbearing age; only a few hundred cases have been reported worldwide. A breast cancer mimic, IGM also is diagnosed by breast biopsy. On December 12, 2008, a physician in Indianapolis, Indiana, reported a cluster of seven IGM diagnoses in multigravid Hispanic women, an unusually high number. To evaluate the etiology of the breast masses and characterize associated epidemiologic and clinical features, the Indiana State Department of Health and CDC conducted a multidisciplinary investigation. This report describes the results of that investigation. A total of nine cases of IGM were confirmed during 2006-2008 in Indianapolis, for an annual prevalence of IGM of 2.4 per 100,000 women aged 20-40 years. The prevalence was 12 times higher among Hispanic women. Among IGM patients at the hospital, a median of 5 months elapsed between symptom onset and diagnostic biopsy. Histopathologic evaluations confirmed IGM. In a case-control study of all seven cases and 21 controls from the hospital, case-patients were significantly more likely than controls to have less than a sixth-grade education (odds ratio [OR] = 12.7), a positive tuberculin skin test (OR = undefined), or a medication allergy (OR = 15.0). No other risk factors were significantly associated with case status. Barriers to accessing health care, including low education level, resulted in delayed care for breast masses. Future research could provide more complete descriptions of the epidemiology and etiology of IGM.