What are the causes of a non-blanching petechial rash?

Causes of Non-Blanching Petechial Rash

Non-blanching petechial rashes have a broad differential diagnosis spanning infectious, autoimmune, hematologic, drug-induced, and mechanical causes, with meningococcal disease being the most critical to exclude despite being rare (1% of cases in febrile children). 1

Life-Threatening Infectious Causes

Meningococcal Disease

• Neisseria meningitidis causes invasive meningococcal disease with petechial or purpuric rash that can rapidly progress to purpura fulminans 2
• Despite being the most feared diagnosis, only 1% of children presenting with fever and non-blanching rash actually have meningococcal disease 1
• The rash typically appears alongside high fever, severe headache, and altered mental status 2

Rocky Mountain Spotted Fever (RMSF)

• The classic petechial rash appears 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 2
• Petechial involvement of palms and soles indicates advanced disease and is associated with severe illness 2
• Up to 20% of RMSF cases may lack rash entirely, and absence of rash is associated with increased mortality 2
• The rash can also occur with Treponema pallidum (secondary syphilis), Streptobacillus moniliformis (rat-bite fever), and E. chaffeensis (ehrlichiosis) 2

Infective Endocarditis

• Petechiae on palms and soles can occur with bacterial endocarditis 2

Viral Causes

• Enteroviruses (coxsackievirus, echovirus) can produce petechial rashes that mimic bacterial causes but typically progress more slowly 3, 4
• Human herpesvirus 6 (roseola), parvovirus B19, and Epstein-Barr virus may present with maculopapular rashes that can include petechial components 2
• Non-specific viral illnesses are the most common cause of petechial rash in well-appearing children 5

Autoimmune and Vasculitic Causes

Rheumatologic Conditions

• Adult-Onset Still's Disease (AOSD) can present with vasculitic purpuric rash, sometimes associated with mixed cryoglobulinemia, characterized by perivascular inflammation with lymphocyte and histiocyte invasion 3, 4
• Rheumatoid arthritis can manifest vasculitic purpuric rash including petechiae 3
• Kawasaki disease should be distinguished from other autoimmune causes, particularly in children 3

Henoch-Schönlein Purpura

• A common cause of petechial/purpuric rash in children, typically involving lower extremities 6

Hematologic Causes

Thrombocytopenia

• Idiopathic thrombocytopenic purpura (ITP) presents with petechiae and purpura due to low platelet counts 6
• Thrombotic thrombocytopenic purpura (TTP) can cause petechial rash alongside systemic manifestations 2

Drug-Induced Causes

Anticoagulant-Related

• Warfarin can cause petechial rash as part of systemic cholesterol microembolization, presenting as "purple toes syndrome" (dark, purplish or mottled color of toes occurring 3-10 weeks after initiation) that blanches on moderate pressure 7
• Warfarin-induced skin necrosis can present with petechiae, particularly in patients with protein C or S deficiency 7

Drug Hypersensitivity

• Drug hypersensitivity reactions can cause petechial rash on palms and soles 2

Mechanical and Traumatic Causes

• Tourniquet phenomenon is a common benign cause in well infants, typically presenting as localized petechiae/purpura on lower limbs (92% of cases), often bilateral 8
• Trauma causing increased capillary pressure can result in petechiae 2
• Postictal petechiae ("trout skin") occur after epileptic seizures due to increased capillary pressure and blood leakage, confined to face, neck, and chest 9
• Coughing, vomiting, or straining can cause petechiae in distribution above the nipple line 5

Other Causes

• Disseminated gonococcal infection 2
• Mycoplasma pneumoniae infection 2
• Leptospirosis 2
• Acute hemorrhagic edema of infancy (benign condition with progression of petechiae) 8

Critical Clinical Pitfalls

• Do not wait for the classic triad of fever, rash, and tick bite in RMSF—it is present in only a minority of patients at initial presentation 2
• Absence of rash does not exclude serious disease: up to 20% of RMSF cases and 50% of early meningococcal cases lack rash 2
• Well-appearing children with localized petechiae (especially lower limbs only) and no fever are more likely to have benign etiologies like mechanical causes 8
• Rash on palms and soles is not pathognomonic for any single condition—consider RMSF, meningococcemia, secondary syphilis, endocarditis, and drug reactions 2
• In darker-skinned patients, petechial rashes may be difficult to recognize, increasing risk of delayed diagnosis 2