In a previously healthy 7‑year‑old child who had a mild viral illness two weeks ago and now presents with sudden widespread bruising and a platelet count of 15 000/µL with an otherwise normal complete blood count, what is the most likely diagnosis?

Immune Thrombocytopenia (ITP) Following Viral Illness

In this previously healthy 7-year-old child with sudden widespread bruising, a platelet count of 15,000/µL, an otherwise normal CBC, and a recent viral illness, the diagnosis is acute immune thrombocytopenic purpura (ITP). 1, 2

Diagnostic Rationale

ITP is the only diagnosis among the options that fits this clinical picture. The key diagnostic features that confirm ITP include: 1, 3

• Isolated thrombocytopenia (platelet count <100,000/µL) with normal hemoglobin and white blood cell count 1, 2
• Sudden onset of hemorrhagic manifestations (bruising, petechiae) without other systemic disease signs 2, 4
• Recent viral illness (2 weeks ago), which precedes acute ITP in approximately 50% of pediatric cases 4, 5
• Normal physical examination except for purpura—no splenomegaly, hepatomegaly, or lymphadenopathy 1, 3, 2

Essential Diagnostic Workup

Bone marrow examination is NOT necessary in this child with typical ITP features. 1, 2 The 2011 American Society of Hematology guidelines represent a major departure from 1996 recommendations by eliminating routine bone marrow aspiration at diagnosis. 1

Required Tests

• Peripheral blood smear review by a hematologist or pathologist to confirm true thrombocytopenia (excluding pseudothrombocytopenia from EDTA-dependent platelet clumping), identify large platelets characteristic of ITP, and exclude schistocytes or abnormal cells 1, 3
• HIV and hepatitis C testing in children with risk factors (not routinely required in all pediatric cases as in adults) 1, 2

Tests NOT Indicated

• Antiplatelet antibody assays—insufficient evidence for routine use and do not change management 1
• Antinuclear antibodies—unnecessary in typical pediatric ITP 1
• Bone marrow examination—only indicated if atypical features present (fever, bone pain, hepatosplenomegaly, abnormal CBC beyond isolated thrombocytopenia, or failure to respond to treatment) 1, 2, 4

Management Strategy

Observation alone is recommended for this child, regardless of the platelet count of 15,000/µL. 1, 2, 6 This represents a fundamental shift in ITP management—treatment decisions are based on bleeding severity, not platelet number. 1

When to Observe (This Patient)

• Skin manifestations only (bruising and petechiae) with no mucous membrane bleeding 1, 2, 6
• Natural history data show 30-70% of children recover from severe thrombocytopenia within 3 weeks without treatment 6
• Risk of intracranial hemorrhage is extremely low (0.1-0.5%) in children with ITP, with most occurring in the first 5 weeks after diagnosis 1, 6, 4

When Treatment IS Required

Treatment should be initiated only if: 1, 2, 6

• Mucous membrane bleeding (epistaxis, oral bleeding, gastrointestinal bleeding) with platelets <20,000/µL 6
• Minor purpura with platelets <10,000/µL 6
• Life-threatening bleeding (intracranial hemorrhage) regardless of platelet count 1, 4

First-Line Treatment Options (If Needed)

If treatment becomes necessary, choose ONE of the following: 1, 2, 4

• IVIg 0.8-1 g/kg as a single dose—preferred when rapid platelet increase is needed 1, 2, 6
• Short course of corticosteroids (prednisone 2-4 mg/kg/day for 7-21 days) 2, 6
• Anti-D immunoglobulin 75 µg/kg (only for Rh-positive patients) 4, 5

Emergency Treatment for Life-Threatening Bleeding

For organ- or life-threatening hemorrhage (e.g., intracranial hemorrhage), multimodality therapy is indicated: 4

• Platelet transfusion
• IV high-dose methylprednisolone (30 mg/kg, maximum 1 g)
• IVIg (1 g/kg)
• Consider emergency splenectomy

Critical Safety Measures

Avoid medications that impair platelet function: 2, 6

• Aspirin
• NSAIDs (ibuprofen, naproxen)
• Other antiplatelet agents

Restrict high-risk activities: 2, 6

• Contact sports
• Activities with high trauma risk

Provide parental education on warning signs requiring immediate evaluation: 6

• Persistent epistaxis
• Oral bleeding
• Blood in stool or urine
• Severe headache
• Altered mental status

Prognosis

Most children (75-80%) achieve spontaneous remission by 6 months. 1, 6 Chronic ITP (persistent thrombocytopenia >12 months) occurs in approximately 20-30% of children. 1 The overall mortality from acute ITP in children is 0.5-0.6%, with fatal intracranial hemorrhage occurring in 0.5% of cases. 1

Common Diagnostic Pitfalls to Avoid

• Never diagnose ITP without reviewing the peripheral blood smear personally—automated counters can miss pseudothrombocytopenia, giant platelets, or schistocytes 3
• Do not overlook secondary causes—splenomegaly, hepatomegaly, or lymphadenopathy excludes primary ITP and mandates investigation for HIV, systemic lupus erythematosus, or lymphoproliferative disorders 1, 3, 2
• Do not treat based on platelet count alone—treatment is indicated only for clinically significant bleeding, not to normalize platelet numbers 1, 2, 6
• Do not use prolonged corticosteroid therapy—significant toxicities in children include growth suppression, immunosuppression, and metabolic effects 6