What is petechiae?

What is Petechiae?

Petechiae are small (1-5 mm in diameter), pinpoint hemorrhagic spots that appear on the skin due to bleeding from capillaries into the skin or mucous membranes. 1

Characteristics of Petechiae

• Petechiae appear as small, round, pinpoint red or purple spots on the skin or mucous membranes 1
• Unlike other rashes, petechiae do not blanch (fade) when pressure is applied 2
• They can be localized to specific body areas or generalized across the body 1
• Petechiae result from microhemorrhages due to damage or dysfunction of small blood vessels 3
• They can range from sparse to numerous and may coalesce to form larger purpuric lesions 1

Common Causes of Petechiae

Infectious Causes

• Tickborne rickettsial diseases such as Rocky Mountain Spotted Fever (RMSF), where petechiae typically appear 5-6 days after onset of fever 1
• Bacterial infections causing sepsis or endocarditis 1
• Viral infections, including certain enteroviruses 1
• Meningococcal infections, which can cause rapidly spreading petechial rash 1

Hematologic/Coagulation Disorders

• Thrombocytopenia (low platelet count) 1
• Coagulation disorders and deficiencies 3
• Leukemias and other blood disorders 4

Vascular/Mechanical Causes

• Increased pressure in blood vessels, such as during severe coughing, vomiting, or seizures 2
• "Tourniquet phenomenon" in infants, where tight clothing or diapers can cause localized petechiae 5
• Trauma to blood vessels 3
• Senile/solar purpura due to age-related vessel wall degeneration 4

Other Causes

• Drug reactions 1
• Vitamin C deficiency (scurvy) 4
• Amyloidosis and other metabolic disorders affecting vessel walls 4
• Post-resuscitation petechiae due to reestablished blood flow in damaged vessels 6
• Vasculitis and pseudovasculitis syndromes 4

Clinical Significance

• Petechiae can be a warning sign of serious conditions requiring immediate medical attention, particularly when accompanied by fever or other systemic symptoms 1
• In Rocky Mountain Spotted Fever, the appearance of petechiae on palms and soles is a classic sign of advanced disease with a 5-10% case-fatality rate if untreated 1
• In stroke patients, hemorrhagic transformation with petechial hemorrhages may occur in approximately 5% of infarctions 1
• Well-appearing infants with localized petechiae without fever typically have benign etiologies 5

Diagnostic Approach

• Evaluate for accompanying symptoms, particularly fever, which may indicate serious infection 1
• Note the distribution pattern - petechiae on palms and soles can suggest RMSF but are not pathognomonic 1
• Consider recent history of trauma, coughing, vomiting, or seizures 2, 6
• Laboratory tests often include complete blood count, coagulation profile, and inflammatory markers 5
• Skin biopsy may be necessary to differentiate true vasculitis from pseudovasculitis 4

Clinical Pearls and Pitfalls

• The classic triad of fever, rash, and reported tick bite is present in only a minority of RMSF patients; absence of rash should not preclude consideration of RMSF 1
• Petechiae can be difficult to visualize in patients with darker skin pigmentation 1
• Petechiae on the face and neck after seizures ("trout skin") can help diagnose seizure when history is unclear 2
• Distinguishing between true vasculitis and pseudovasculitis is crucial to avoid unnecessary immunosuppressive therapy 4
• In children, petechial rashes often develop earlier and more frequently than in adults with the same conditions 1