From the Guidelines
The diagnostic evaluation for a petechial rash on both feet in a 16-year-old girl should start with a thorough history and physical examination, including questions about recent tick bites, fever, and other symptoms, as the rash could be indicative of Rocky Mountain Spotted Fever (RMSF) or meningococcal septicaemia 1.
Key Considerations
- The presence of a petechial rash, particularly on the feet, is a significant finding that warrants immediate attention, as it can be a sign of a serious underlying condition such as RMSF or meningococcal septicaemia.
- A fever and reported tick bite are important components of the history, but their absence does not rule out RMSF, as the classic triad of fever, rash, and tick bite is present in only a minority of patients during initial presentation 1.
- The rash in RMSF typically begins as small, blanching, pink macules on the ankles, wrists, or forearms and may evolve to petechiae over the next several days of illness 1.
- In cases of suspected meningococcal septicaemia, urgent hospital assessment and parenteral antibiotics are recommended, even before hospital admission 1.
Diagnostic Approach
- The initial evaluation should include a complete blood count (CBC) and peripheral blood smear to assess for thrombocytopenia or other abnormalities that may suggest an underlying condition such as immune thrombocytopenia (ITP) 1.
- Further testing, such as bone marrow evaluation, may be necessary if the initial evaluation suggests an underlying condition other than ITP or if the patient's symptoms and laboratory results are not typical of ITP 1.
- It is essential to consider the patient's overall clinical presentation, including any additional symptoms, medical history, and physical examination findings, when determining the diagnostic approach and potential underlying causes of the petechial rash.
From the Research
Diagnostic Evaluation for Petechial Rash
The diagnostic evaluation for a petechial rash on both feet in a 16-year-old girl involves a thorough history and physical examination, followed by consideration of red flags 2. The presence of fever and systemic signs of illness should be assessed, and the rash should be categorized based on its morphologic characteristics, such as petechial/purpuric, erythematous, maculopapular, or vesiculobullous 2.
Possible Causes of Petechial Rash
Possible causes of petechial rash in children include:
- Viral infections, such as parvovirus B19 3
- Bacterial infections, such as meningococcal disease 4
- Non-specific viral illnesses 5
- Viral single- and co-infections 6
Diagnostic Approach
The diagnostic approach for a petechial rash in a child involves:
- Complete blood count 4
- Inflammatory tests 4
- Coagulation tests 4
- Monospot test 4
- Nasopharyngeal rapid tests 4
- Blood culture 4
- Cerebrospinal fluid culture (where appropriate) 4
- Quantitative real-time polymerase chain reaction to identify viral pathogens 6
Clinical Characteristics
Clinical characteristics that may be associated with serious illness in children with petechial rash include: