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Case report
Mycobacterium mucogenicum skin and soft tissue infection of the breast mimicking idiopathic granulomatous mastitis
  1. Karen Krueger1 and
  2. Lauren M Guggina2
  1. 1Division of Infectious Diseases, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
  2. 2Department of Dermatology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
  1. Correspondence to Dr Karen Krueger; Karen.krueger{at}


We present a case of a 28-year-old woman who came to medical attention after noticing a breast mass associated with an overlying eroded plaque of the skin. A core biopsy of the breast mass was negative for malignancy but demonstrated granulomatous inflammatory changes. Acid-fast bacilli and Gomori methenamine-silver stains were negative for microorganisms. The patient was diagnosed with presumptive idiopathic granulomatous mastitis and started on oral steroids. Her symptoms progressed. Tissue culture from a repeat biopsy grew Mycobacterium mucogenicum. The patient responded well to combination oral antimicrobial therapy.

  • dermatology
  • infectious diseases

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  • Contributors KK and LMG both provided clinical care for the patient and contributed to the writing of the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.