Causes of New Onset Petechiae

Life-Threatening Infectious Causes

The Centers for Disease Control and Prevention recommends immediate evaluation for life-threatening infectious causes, particularly meningococcemia and Rocky Mountain Spotted Fever, in patients with new onset petechiae 1, 2, 5
Neisseria meningitidis causes rapidly progressive petechial or purpuric rash that can evolve to purpura fulminans within hours, presenting with high fever, severe headache, altered mental status, and rash that progresses more rapidly than RMSF 1, 2, 3
Rocky Mountain Spotted Fever presents with classic petechial rash by day 5-6 of illness, beginning as small blanching pink macules on ankles, wrists, or forearms that evolve to maculopapular lesions with central petechiae, and petechial involvement of palms and soles indicates advanced disease and severe illness 5, 6

The American Academy of Pediatrics recommends complete blood count to assess platelet count in patients with unexplained petechiae, as immune thrombocytopenic purpura (ITP) can present with petechiae as initial manifestation 9
Thrombotic thrombocytopenic purpura (TTP) causes petechial rash with systemic manifestations, and mild hemophilia (factor VIII or IX deficiency) may not cause aPTT abnormalities but can still result in significant bleeding 1, 9

The Centers for Disease Control and Prevention recommends immediate assessment when fever with petechiae is present, considering meningococcemia or RMSF, and systemic symptoms such as severe headache, altered mental status, hypotension, rapidly progressive rash, and petechiae involving palms and soles 1, 5, 2
Laboratory evaluation should include complete blood count with platelet count for all patients with unexplained petechiae, PT, aPTT, and fibrinogen if bleeding disorder suspected, and blood cultures if febrile or systemically ill 9, 3, 5