AKT · Haematology/Bleeding & clotting

Thrombocytopenia & ITP

Low platelets — reduced production, increased destruction (immune/consumption), or sequestration

Overview

A low platelet count, causing a platelet-type bleeding pattern (mucocutaneous — petechiae, purpura, epistaxis, menorrhagia). Causes split into reduced production (marrow failure/infiltration, drugs, alcohol, B12/folate), increased destruction (immune thrombocytopenia/ITP, drug-induced, DIC, TTP/HUS) and sequestration (hypersplenism). ITP is an autoimmune (often post-viral in children) isolated thrombocytopenia and a diagnosis of exclusion.

Recognise

Mucocutaneous bleeding: petechiae, purpura, easy bruising, epistaxis, gum/menstrual bleeding; spontaneous bleeding risk rises as platelets fall (especially <20)
ITP: ISOLATED thrombocytopenia with otherwise normal FBC/film; children — acute, post-viral, self-limiting; adults — often chronic
Look for clues to a specific cause: schistocytes (TTP/HUS/DIC), blasts (leukaemia), pancytopenia (marrow), heparin exposure (HIT)

Red flags

Thrombocytopenia + schistocytes (microangiopathy — TTP/HUS/DIC) → emergency; in TTP do NOT give platelets
Major/intracranial bleeding, or heparin-induced thrombocytopenia (HIT — falling platelets + thrombosis ~5–10 days into heparin) → stop heparin, switch anticoagulant

Differentials & how to tell them apart

TTP / HUS / DIC (microangiopathy)thrombocytopenia + schistocytes ± renal/neuro involvement — emergency, distinct management

Heparin-induced thrombocytopenia (HIT)platelet fall + THROMBOSIS 5–10 days into heparin — stop heparin, use a non-heparin anticoagulant

PseudothrombocytopeniaEDTA-induced platelet clumping — repeat in citrate; no bleeding

Marrow failure/leukaemiaother cytopenias/blasts — not isolated

Investigations

FBC + blood FILM (exclude pseudothrombocytopenia/EDTA clumping; look for schistocytes/blasts); coagulation/fibrinogen (DIC); ITP is a diagnosis of exclusion (no other cause); HIT antibodies if heparin-exposed; B12/folate, autoimmune/virology; marrow if other lines abnormal/atypical.

Management

ITP → steroids ± IVIG (platelets only for life-threatening bleed); treat the specific cause

1Confirm a true low platelet count on a blood FILM (exclude EDTA clumping) and look for the cause — isolated (ITP) vs schistocytes (microangiopathy) vs blasts/pancytopenia (marrow) vs heparin (HIT). ITP is a diagnosis of exclusion.Gate: Schistocytes + thrombocytopenia = TTP/HUS/DIC (emergency — in TTP do NOT give platelets); a platelet fall + thrombosis on heparin = HIT (stop heparin, switch to a non-heparin anticoagulant).
2ITP → observe if mild, else corticosteroids ± IVIG (platelets only for life-threatening bleeding); refractory → TPO-receptor agonist/rituximab/splenectomy. Treat the specific cause for other thrombocytopenias.

ITP: observe if mild/asymptomatic; corticosteroids ± IVIG first-line for bleeding/very low counts — IVIG for rapid rise (e.g. before surgery/active bleeding); platelets only for life-threatening bleeding

ITP second-line: thrombopoietin-receptor agonists, rituximab, splenectomy — for chronic/refractory disease

Treat the specific cause — stop the culprit drug; HIT → stop heparin + non-heparin anticoagulant; TTP → plasma exchange (NO platelets)

Platelet transfusion for production failure/bleeding — NOT in TTP/HIT (worsens microthrombi/thrombosis)

Key points

Low platelets → film first (exclude EDTA clumping), then find the cause. ITP = ISOLATED thrombocytopenia, diagnosis of exclusion (children post-viral self-limiting) → steroids ± IVIG; platelets only for life-threatening bleeding. TRAPS: schistocytes = TTP/HUS/DIC (TTP — NO platelets, plasma exchange); platelet fall + thrombosis on heparin = HIT (stop heparin).

Monitor & prognosis

Platelet count/bleeding, response to steroids/IVIG, the underlying cause.

Childhood ITP usually self-limits; adult ITP often chronic but manageable; microangiopathy/HIT serious.

Source: BSH ITP; cross-ref haemolytic anaemia (TTP/HUS)