A 50–year–old Caucasian woman presented to the emergency department with worsening left breast redness and nipple discharge for 3 days. Examination was significant for erythema encompassing most of the left breast with yellow discharge and inferolateral sloughing of the nipple. Ultrasound breast was consistent with mastitis. She was started on IV vancomycin and metronidazole after discussing with Infectious Diseases (ID) specialist. There was mild improvement in erythema and she was discharged on day 3 with oral doxycycline. Two days after discharge, she visited the ID clinic with worsening breast pain and discharge. On further probing, she disclosed history of cold sores in her husband following which she was started on oral acyclovir for presumed herpes simplex virus (HSV) mastitis. The nipple discharge which was sent for viral culture yielded HSV–1. She completed 10 day course of acyclovir and her symptoms resolved completely.
Mastitis typically occurs in infants younger than two months of age and lactating women. However, breast infection also may occur in adults. Factors that predispose to breast infection in nonlactating adults include trauma (breast manipulation during sexual activity, shaving or plucking periareolar hair, nipple piercing), obesity and mammary duct ectasia. Nonlactational mastitis is most commonly caused by S. aureus but may also be caused by Enterococcus, Streptococcus pyogenes, anaerobic Streptococci, and viruses. Mastitis due to Herpes Simplex virus constitutes less than 2% of all extragenital herpes lesions. Mastitis as the first and sole manifestation of clinically apparent HSV infection without oral/genital lesions is rare. Many cases of maternal–infant transmission of the virus during breast–feeding resulting in nipple lesions have been documented. HSV mastitis in nonlactating women is rarely reported. The modes of transmission are autoinoculation from asymptomatic oral or genital lesions, reactivation from subclinical infection of breast and primary infection from recent sexual contact with an infected person/asymptomatic carrier. Crusted lesions with ulceration limited to the tip of the nipple or extending to the areola are typical of HSV mastitis. Extensive skin erythema with skin thickening and peau d’orange appearance may also be seen. Tissue culture is the most sensitive and specific method of diagnosis. Oral acyclovir for 7–10 days is the treatment of choice. It is important to differentiate this from breast abscess as Herpes mastitis heals in 7–10 days without scarring while the latter requires surgical drainage and heals with residual scarring. It is also important to differentiate HSV mastitis from zoster mastitis in which lesions are confluent and hemorrhagic and heal slowly with scarring and residual neuralgia.
With this case, we emphasize the importance of considering HSV infection in patients with ulcerating mastitis.
Figure 1Breast ultrasound demonstrating edema of the underlying parenchyma consistent with mastitis.