HaematologyTier 1Disease (DEADMAN)

Immune thrombocytopenia

Description

Isolated thrombocytopenia from autoantibody-mediated platelet destruction + impaired production
Diagnosis of exclusion - no specific confirmatory test
Primary (idiopathic) vs secondary (SLE, CLL/lymphoma, HIV/HCV, drugs, post-vaccination)

Bimodal: children (often post-viral, acute, self-limiting) and adults (chronic, F>M)
Adult incidence ~2-4 per 100,000/yr
Children: majority resolve spontaneously within 12 months
Adults: majority become chronic (>12 months)

Autoantibodies (usually anti-GPIIb/IIIa or GPIb/IX) opsonise platelets -> splenic (reticuloendothelial) clearance
Also impaired megakaryocyte platelet production - not pure peripheral destruction
Secondary causes: SLE, APLS, CLL, lymphoma, HIV, HCV, H. pylori, drugs (heparin - distinguish HIT, quinine), post-viral/post-vaccination in children

Isolated thrombocytopenia on FBE, otherwise normal blood count and film (no schistocytes - excludes TTP/HUS/DIC, no blasts - excludes leukaemia)
Diagnosis of exclusion - no platelet antibody test routinely used (poor sensitivity/specificity)
Work-up: film, HIV/HCV serology, H. pylori (if GI symptoms), ANA if clinical SLE features; bone marrow not routine unless atypical features (age, other cytopenias, organomegaly) or poor treatment response
Bleeding risk correlates poorly with platelet count alone - assess clinical bleeding (skin/mucosal) as well as the number

By bleeding risk, not count alone

ASH 2026 guideline - treat significant bleeding or high bleeding-risk, not an asymptomatic number

No/minor bleeding, platelets not critically low - observe, avoid antiplatelets/NSAIDs/anticoagulants, safety-net
Significant mucocutaneous bleeding or platelets very low with risk factors -> treat

First-line

Corticosteroids (prednisolone, or dexamethasone pulse) - most patients
IVIg - rapid rise (hours-days), used for urgent bleeding or pre-procedure, or steroid-contraindicated
Anti-D immunoglobulin - alternative in Rh(D)-positive, non-splenectomised patients (limited availability)

Second-line (persistent/chronic, relapse after first-line)

TPO-receptor agonists (romiplostim, eltrombopag) - ASH 2026 preferred over rituximab as second-line
Rituximab - alternative, less durable response typically
Splenectomy - reserved for refractory disease after >12 months, durable response in a majority but permanent asplenia risk (vaccination + prophylaxis needed)

Emergency (life-threatening bleeding)

IV methylprednisolone + IVIg + platelet transfusion (even though normally ineffective alone) +/- TXA

SLE, antiphospholipid syndrome (Evans syndrome = ITP + autoimmune haemolytic anaemia)
CLL, lymphoma
HIV, hepatitis C, H. pylori
Common variable immunodeficiency
Pregnancy - gestational thrombocytopenia is the main differential, usually milder/later onset

Children - majority remit spontaneously within 12 months
Adults - majority develop chronic ITP, relapsing-remitting course common
Intracranial haemorrhage - rare but the feared complication, more likely at very low counts + trauma
Treatment aims to prevent bleeding, not normalise the count - do not chase a number

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