SN8 SHORT NOTE 5M

Write a short note on thrombocytopenia, including immune thrombocytopenic purpura.

General Medicine · Final Professional

Definition

Thrombocytopenia is a platelet count below 150 × 10⁹/L. Clinically:

100–150 × 10⁹/L — usually asymptomatic
50–100 × 10⁹/L — bleeding with trauma or surgery
20–50 × 10⁹/L — easy bruising and mucosal bleeding
< 20 × 10⁹/L — spontaneous bleeding; risk of intracranial haemorrhage below 10

Causes

Mechanism	Causes
Decreased production	Marrow failure — aplastic anaemia, leukaemia, myelodysplasia, marrow infiltration (lymphoma, myeloma, metastases, myelofibrosis); megaloblastic anaemia; drugs (chemotherapy, alcohol, chloramphenicol, linezolid); viral marrow suppression; congenital
Increased destruction — immune	Immune thrombocytopenic purpura (ITP); drug-induced (heparin, quinine, sulphonamides, rifampicin, valproate); SLE and antiphospholipid syndrome; HIV, hepatitis C; post-transfusion purpura; neonatal alloimmune
Increased destruction — non-immune	DIC; thrombotic thrombocytopenic purpura (TTP); haemolytic uraemic syndrome; severe sepsis; dengue and other viral fevers (a leading cause in India); malaria; giant haemangioma (Kasabach–Merritt); prosthetic valve
Sequestration	Hypersplenism — portal hypertension and cirrhosis, chronic malaria, kala-azar, lymphoproliferative disease
Dilutional	Massive transfusion, fluid resuscitation
Pseudothrombocytopenia	EDTA-induced platelet clumping in vitro — a laboratory artefact; always confirm a low count by examining the smear and, if necessary, repeating in a citrate tube

Clinical Features — the Pattern Matters

Thrombocytopenic bleeding is "platelet-type": petechiae, purpura and ecchymoses, mucosal bleeding (epistaxis, gum bleeding, menorrhagia, gastrointestinal and urinary bleeding), and immediate bleeding after injury. This contrasts with "coagulation-factor-type" bleeding (as in haemophilia): deep haematomas, haemarthroses and delayed bleeding.

Serious manifestations: intracranial haemorrhage (rare but the leading cause of death), retinal haemorrhage, and major gastrointestinal bleeding.

Look for clues to the cause: fever and sepsis, splenomegaly (sequestration), lymphadenopathy and hepatosplenomegaly (malignancy), stigmata of chronic liver disease, drug history, recent viral illness, and features of SLE.

Investigations

Repeat the count and examine the peripheral smear — this is the essential first step. It excludes pseudothrombocytopenia (clumping), and reveals schistocytes (TTP, HUS, DIC), blasts, dysplasia, large platelets (ITP, congenital), and malarial parasites.
Coagulation profile with fibrinogen and D-dimer — to identify DIC.
Renal and liver function, LDH, reticulocytes and direct Coombs test — to identify microangiopathy and haemolysis.
Viral serology: HIV, hepatitis B and C; dengue NS1 and serology; malaria smear and rapid test.
ANA, antiphospholipid antibodies, thyroid function.
Vitamin B12 and folate.
*H. pylori* testing — eradication improves platelet counts in a proportion of ITP patients.
Bone marrow examination — not required in typical ITP in a young patient, but indicated where there are additional cytopenias, abnormal cells on the smear, organomegaly, age over 60, or failure to respond to first-line treatment.

Immune Thrombocytopenic Purpura (ITP)

Definition: an acquired autoimmune disorder characterised by isolated thrombocytopenia (platelets < 100 × 10⁹/L) in the absence of other causes, due to IgG autoantibodies against platelet glycoproteins (GPIIb/IIIa) causing splenic destruction, together with impaired platelet production.

It is a diagnosis of exclusion — there is no confirmatory test.

Feature	Acute ITP	Chronic ITP
Typical patient	Children, 2–6 years	Adults, women 20–40
Preceding illness	Viral infection or vaccination 1–3 weeks before	Usually none
Onset	Abrupt	Insidious
Duration	Self-limiting — resolves within 6 months in 80–90%	> 12 months; relapsing course
Treatment	Often observation alone	Usually requires treatment

Clinical features: isolated thrombocytopenia with petechiae, purpura and mucosal bleeding, in an otherwise well patient. Splenomegaly is characteristically ABSENT — its presence should make you doubt the diagnosis and look for another cause.

Management of ITP:

Observation for platelets above about 30 × 10⁹/L without bleeding, particularly in children — many need no treatment at all.
First line: corticosteroids (prednisolone or high-dose dexamethasone pulses) and/or intravenous immunoglobulin — IVIG works fastest and is preferred when a rapid rise is needed (active bleeding, before surgery, in pregnancy). Anti-D immunoglobulin is an alternative in Rh-positive non-splenectomised patients.
Second line: thrombopoietin receptor agonists (eltrombopag, romiplostim), rituximab, and splenectomy (which produces durable remission in about two-thirds, but is now used later given effective medical options; vaccinate against encapsulated organisms beforehand).
Refractory disease: immunosuppressants (azathioprine, mycophenolate, ciclosporin), fostamatinib.
Emergency management of life-threatening bleeding: platelet transfusion (given despite the immune destruction, in this situation only), high-dose IVIG, high-dose corticosteroid, and tranexamic acid, with consideration of emergency splenectomy.
Avoid aspirin, NSAIDs and anticoagulants; advise against contact sports; treat *H. pylori* where present.

DANGER / REMEMBER

Do not transfuse platelets in TTP or HIT — in thrombotic thrombocytopenic purpura and heparin-induced thrombocytopenia, platelet transfusion "adds fuel to the fire", promoting further microvascular thrombosis, and can precipitate stroke or myocardial infarction. TTP presents with the pentad of thrombocytopenia, microangiopathic haemolytic anaemia with schistocytes, fever, renal impairment and fluctuating neurological signs, and is treated as an emergency with plasma exchange (plus steroids, rituximab and caplacizumab), not with platelets. Distinguishing ITP from TTP at the bedside — by looking for schistocytes, haemolysis and neurological signs — is a decision that saves lives.

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