Acute mastoiditis in a newborn with 11 days of life: Case report.

Acute mastoiditis is a potentially life-threatening complication and extremely rare in children under six months. We herein report the case of a 11-days-old newborn with acute mastoiditis complicated by subperiosteal abscess, submitted to surgical and medical treatment. A transient hypogammaglobulinemia was finally diagnosed and successfully managed without complications. Early recognition of this rare immunological disorder and prompt intervention are critical to prevent further complications.