From the Guidelines
A petechial rash workup should begin with a thorough history and physical examination to determine potential causes, which include infections, platelet disorders, vasculitis, or medication reactions, and initial laboratory tests should include a complete blood count with platelet count, coagulation studies, and basic metabolic panel, as recommended by the most recent guidelines 1. The workup for a patient presenting with a petechial rash should prioritize identifying life-threatening conditions such as meningococcemia or Rocky Mountain spotted fever, which can be indicated by fever, altered mental status, hypotension, or rapidly spreading rash.
- Initial steps should include:
- A thorough history to identify potential exposures, such as tick bites for Rocky Mountain spotted fever 1, or recent travel and contact history for meningococcemia 1.
- Physical examination to assess the extent and characteristics of the rash, as well as signs of systemic illness.
- Laboratory tests:
- Complete blood count (CBC) with platelet count to evaluate for thrombocytopenia or other hematologic abnormalities.
- Coagulation studies (PT/INR, PTT) to assess for coagulopathy.
- Basic metabolic panel to evaluate for signs of organ dysfunction.
- Blood cultures and viral studies if infection is suspected, particularly for meningococcemia, Rocky Mountain spotted fever, or viral hemorrhagic fevers.
- For suspected autoimmune causes, additional tests may include antinuclear antibody testing, rheumatoid factor, and complement levels.
- In cases of suspected vasculitis, consider ANCA testing and skin biopsy.
- Medication history is crucial as many drugs can cause petechiae through immune-mediated mechanisms or direct platelet effects.
- Urgent evaluation and treatment are necessary if the patient presents with signs of severe illness, as delays in diagnosis and treatment can significantly impact morbidity and mortality, especially in conditions like meningococcemia 1 and Rocky Mountain spotted fever 1.
From the Research
Appropriate Workup for Petechial Rash
The workup for a patient presenting with a petechial rash involves a combination of physical examination, laboratory tests, and careful consideration of the patient's overall clinical presentation.
- The initial evaluation should include a thorough history and physical examination to identify any potential causes of the rash, such as trauma, infection, or bleeding disorders 2.
- Laboratory tests may include a complete blood count, coagulation tests, and inflammatory markers, such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) 3.
- In some cases, additional tests such as blood cultures, nasopharyngeal rapid tests, and cerebrospinal fluid culture may be necessary to rule out serious infections like meningococcal disease 3.
- The National Institute for Health and Care Excellence (NICE) pathway for management of petechial rash in children provides a framework for clinicians to follow 2.
- For well-appearing infants with localized purpura and/or petechiae, a period of observation (4 hours) may be sufficient, and further investigation may not be necessary if there is no progression of signs 4.
Considerations for Serious Illness
Certain clinical features are strongly associated with serious illness in patients with petechial rash, including: