A child with bruising and a low platelet count — long case

Candidate instructions (10-minute long-case discussion)

You are the paediatric registrar in the emergency department. A previously well four-year-old boy presents with three days of increasing bruising over the limbs, a petechial rash over the ankles, and two episodes of epistaxis. He is afebrile, active and cheerful, with no hepatosplenomegaly or lymphadenopathy. His full blood count shows a haemoglobin of 124 g per litre, a white-cell count of 7.2 × 10⁹ per litre, a neutrophil count of 3.1 × 10⁹ per litre, and a platelet count of 10 × 10⁹ per litre, with a normal film showing no blasts. The examiner asks you to discuss the triage, the diagnosis and the exclusion of leukaemia, the management, the safety-netting, and the safeguarding assessment of his bruising. [3]

Your tasks are: [3]

1. Outline the triage of this child and how the sick-versus-well split directs your pathway. [2]
2. State the diagnosis and explain how you confirm it and exclude leukaemia. [3]
3. Outline the management, including when you would treat and with what, and the safety-netting for serious bleeding. [1]
4. Discuss how you would apply the safeguarding assessment to a bruising presentation, and what would change the picture to IgA vasculitis. [12]

You are not expected to manage refractory or chronic ITP independently — haematology is involved — but you should explain the first-line approach and the indications for referral. [2]

Examiner discussion points

On the triage. The examiner will expect the candidate to run the sick-versus-well split in the first minute: this child is afebrile, active and well, with isolated bruising and petechiae, so he is in the diagnostic rather than the emergency pathway, and there is no need for the first-hour sepsis bundle. The candidate should confirm the rash is non-blanching with the glass test and describe it, and state that the well child still needs a full blood count and a film before a diagnosis is made. [2]

On the diagnosis and the exclusion of leukaemia. The diagnosis is acute immune thrombocytopenia, defined by a platelet count under 100 × 10⁹ per litre with isolated thrombocytopenia and a normal film in an otherwise well child. The candidate should confirm the haemoglobin, white-cell and neutrophil counts are normal, that the film shows no blasts, and that there is no organomegaly or lymphadenopathy, and state that isolated thrombocytopenia with pancytopenia, blasts or organomegaly is leukaemia, not primary ITP. The paediatric ITP update reinforces excluding inherited platelet disorders and secondary causes before labelling a child. [3] [4]

On the management and safety-netting. The candidate should apply the ASH 2019 risk-based approach: match treatment to the bleeding severity rather than the count alone. For dry purpura with an acceptable count, observation and safety-netting may suffice, though many treat when the count is very low; for wet purpura, active bleeding, or high-risk activities, first-line options are a short course of corticosteroids, intravenous immunoglobulin, or anti-D immunoglobulin in an Rh-positive, non-splenectomised child. The candidate should avoid steroids if any atypical feature is present, and should give clear written safety-netting for head injury, uncontrolled bleeding, new petechial spread and any neurological symptom suggesting intracranial haemorrhage, with avoidance of contact sports and intramuscular injections while the count is low. [2] [1]

On safeguarding and the IgA vasculitis variant. The candidate should apply the TEN-4 FACES bruising pattern to any bruising presentation — bruising on the Torso, Ear or Neck, any bruise in an infant four months or younger, and facial bruising — and refer to the child-protection team when the pattern or the developmental history does not fit. The candidate should state that a four-year-old who is mobile and bruises over the limbs in a pattern consistent with activity, with isolated thrombocytopenia and a clean film, fits ITP rather than abuse, but that an inconsistent history or a TEN-4 distribution would escalate to safeguarding. If the picture were palpable purpura on the lower limbs and buttocks with abdominal pain or arthritis, the candidate should shift to IgA vasculitis, check the blood pressure and urinalysis now and for six to twelve months, and manage supportively with steroids reserved for severe gut or renal disease. [12] [5]

Model answer summary

The fellowship answer recognises that a well child with sudden bruising and isolated thrombocytopenia on a clean film has immune thrombocytopenia, whose management is risk-based — observation or first-line corticosteroids or intravenous immunoglobulin matched to the bleeding, with rigorous safety-netting for the rare but catastrophic intracranial haemorrhage. The key judgement is the film and the lines: isolated thrombocytopenia is ITP, while pancytopenia, blasts or organomegaly is leukaemia and changes everything. Safeguarding is applied to every bruise with the TEN-4 FACES pattern, and a shift to palpable dependent purpura with abdominal or joint symptoms turns the diagnosis to IgA vasculitis with months of renal monitoring — because the non-blanching rash is a triage problem whose first split, the blood film and the bruising pattern together keep the dangerous diagnoses caught and the common ones managed calmly. [1] [12]