Skip to Main Content

We have a new app!

Take the Access library with you wherever you go—easy access to books, videos, images, podcasts, personalized features, and more.

Download the Access App here: iOS and Android

Clinical Summary

Neonatal mastitis is an infection of the breast tissue that occurs in full-term neonates. The peak incidence of mastitis without abscess is in the 2nd week of life and the 4th week of life for mastitis with abscess. Females are affected more often than males in a 2:1 distribution. Clinically, it manifests as swelling, induration, erythema, warmth, and tenderness of the affected breast. The ipsilateral axillary lymph nodes may be swollen. Approximately 50% develop an abscess. In some cases, purulent discharge may be expressed from the nipple. Fever may be present in 25% of affected patients. Other systemic symptoms (irritability, decreased appetite, and vomiting) are less common but indicate a more severe infection if present. Bacteremia is rare. Staphylococcus aureus, specifically methicillin-resistant strains (MRSA), is the most common pathogen, causing 75% to 85% of cases. Rarely, gram-negative organisms or group B or D streptococci are the cause. If treatment is delayed, mastitis may progress rapidly with involvement of subcutaneous tissues and subsequent toxicity. In the initial stages, neonatal mastitis may mimic mammary tissue hypertrophy owing to maternal passive hormonal stimulation. Minor trauma, cutaneous infections, and duct blockage may precede this infection.


Neonatal Mastitis. Neonate with left-sided breast swelling, erythema, and purulent discharge. (Photo contributor: Lawrence B. Stack, MD.)

Management and Disposition

Immediate treatment is important to avoid cellulitic spread and breast tissue damage. Well-appearing infants under 2 months of age should be admitted and treated with antistaphylococcal monotherapy. In areas of high MRSA prevalence, choose clindamycin or vancomycin. If MRSA is not a concern, nafcillin is appropriate. Adjustment of coverage can be made if results of cultures or Gram stain are available, especially in the presence of gram-negative bacilli. In cases involving systemic signs of infection, rapid subcutaneous spread, or toxic appearance, a complete sepsis workup should be performed followed by hospitalization. If no organism is seen on Gram stain, a parenteral antistaphylococcal penicillin plus an aminoglycoside or cefotaxime alone should be used. Local MRSA prevalence should determine whether coverage is necessary. In cases of palpable fluctuance or abscess, ultrasound and prompt surgical consultation should be obtained to assess the need for incision and drainage. Conservative treatment with intravenous (IV) antibiotics often results in resolution of the fluctuance without surgical intervention. Recovery is usually within 5 to 7 days.


  1. Antibiotic choice should include coverage for S aureus and possibly MRSA depending on local prevalence.

  2. Maintain a low threshold for initiating a sepsis workup.

  3. Mastitis is typically a clinical diagnosis, but if there is uncertainty, ultrasound is useful for further characterization.


Neonatal Mastitis. Neonate with marked swelling, erythema, and purulent discharge. (Photo contributor: Emergency Medicine Department, Naval Medical Center, Portsmouth, VA.)

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.