A detailed history and physical examination are paramount for every child presenting with petechiae. Key features in the history include the time of onset, anatomical pattern and a detailed chronological account of any other symptoms, e.g., fever, coughing, vomiting, any recent URTI or gastroenteritis, and any sick contacts. A rapidly spreading rash is more concerning for IMD in an unwell child with a fever. A recent viral infection (URTI or gastroenteritis) is common in ITP, HSP, and HUS. Petechiae confined to above the nipple line are associated with bouts of vomiting or coughing. It is also important to ask about any bleeding from mucosal surfaces such as gingival bleeding, epistaxis, melena, among others. As always, the clinician should confirm vaccination status.

On examination, a complete set of observations and neurological status requires monitoring. A full systemic examination should be completed, including cardiac, respiratory, abdominal, otorhinolaryngological, and neurological (if concerns of IMD). The skin should undergo thorough examination from head to toe, and the pattern of rash requires clear documentation. Demarcating areas of petechiae with a skin marker can help monitor the progression of the rash in clinical practice.

The age of the child can be useful in reaching the most likely diagnosis, for example, a neonate with petechiae could have a NAIT or a TORCH infection, and HSP is more common in the 2 to 5 year age range.

Patterns of concerning symptoms and signs presenting with petechiae include but are not limited to:

• Pyrexia, tachycardia and rapidly spreading petechiae: IMD
• Pallor, bruising, weight loss, lymphadenopathy: Malignancy
• Hypertension: Renal disease associated with HUS, HSP or SLE
• Unusual patterns of petechiae with bruising, an inconsistent history or signs of injury or neglect: NAI

Investigations to diagnose the cause of a petechial rash depend on the clinical presentation and can differ from one PED to another. Adhering to the local protocol is advised. In general, investigations will depend on the location of petechiae, associated pyrexia, or clinical suspicion for any of the concerning patterns of signs and symptoms. A healthy child with scattered petechiae of obvious causation, e.g., known trauma or petechiae confined to above the nipple line, may not require any investigations. At the very least, the healthy child, as described, should be observed for 4 hours before discharge.

• Complete blood count (CBC) to check platelet number, a raised or decreased white cell count or decreased hemoglobin.
• If concerns about IMD or other infection: C-reactive protein, blood culture
• Coagulation profile, urea, electrolytes, and liver function tests may be necessary in some cases (DIC, IMD, HSP, HUS). A prolonged prothrombin time can indicate factor deficiencies, vitamin K deficiency, DIC, liver, or renal disease.
• Urine dipstick and microscopy are useful when renal causes are part of the differential (HSP, HUS, SLE), to check for proteinuria in particular.
• Further tests may be later requested when narrowed down to a more specific diagnosis.

Many patients attending the PED with petechial rashes will not require any specific treatment. If a child remains well after a period of observation, with no spreading of the rash, a normal platelet count and no physical signs or signs of infection on blood tests, they may be discharged home. If IMD is likely, urgent intravenous antibiotics as per local guidelines should be administered, with close observations after admission to the ward. Some patients may receive a dose of antibiotics pre-hospital if high clinical suspicion of IMD is present. If there are specific diagnoses, for example, HSP or ITP, and there is no risk of going home, the child may be discharged with an appointment to return to the appropriate outpatient department and condition-specific education. Other conditions will require admission and treatment, for example, urgent referral to oncology inpatient services for a patient with pancytopenia and probable malignant diagnosis.[8][9]

• Ecchymosis

• Palpable purpura

• Retiform purpura

Recognizing the full range of possible diagnoses for a child presenting with petechiae is essential for any clinician working in the PED. Public health campaigns have increased recognition of petechiae, therefore, allaying parents' fears and concerns is a crucial role, in addition to educating them on red flag signs that should prompt return to the PED.

There are many causes of petechiae, and condition management is optimally by an interprofessional team that includes clinicians, specialists as indicated, hematology nurses, and pharmacists. The key is to determine the primary cause. Most patients with a benign cause or drug-induced petechiae have a good outcome when discontinuing the offending agent. However, when petechiae are due to heparin, paradoxical thrombosis can occur.[10] Cross-disciplinary communication and collaboration of the entire interprofessional healthcare team will guide these cases to the optimal outcome. [Level 5]