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Describe immune thrombocytopenic purpura with its types, features and management.

Pathology · 2nd Professional — Para-Clinical

Definition

Immune thrombocytopenic purpura (ITP) is an acquired disorder in which autoantibodies (usually IgG) against platelet glycoproteins cause premature destruction of platelets in the spleen.

Antibodies are directed against GpIIb/IIIa and GpIb/IX
Antibody also impairs megakaryocyte production, so the compensatory rise is inadequate — which is why thrombopoietin receptor agonists work

Acute and Chronic Forms

Feature	Acute ITP	Chronic ITP
Age	Children, 2–6 years	Adults, 20–40
Sex	Equal	Female to male 3:1
Preceding illness	Viral infection or vaccination 1–3 weeks before, in about 80%	Usually none
Onset	Abrupt	Insidious
Platelet count	Often below 20,000	Variable
Course	Self-limiting — over 80% recover spontaneously in 6 months	Persistent; remissions and relapses
Treatment	Often observation alone	Steroids, immunoglobulin, splenectomy, rituximab

Clinical Features and Investigation

Petechiae, purpura and ecchymoses; epistaxis, gum bleeding, menorrhagia; wet purpura (mucosal blood blisters) indicates a higher risk
Intracranial haemorrhage is rare but the feared complication
NO splenomegaly — its presence argues against the diagnosis and suggests another cause
Platelet count is low; all other counts are normal
Peripheral smear — reduced platelets, often large (young) platelets; no other abnormality
Bone marrow — normal or increased megakaryocytes, confirming that production is not the problem; marrow examination is reserved for atypical cases or before splenectomy

CLINICAL PEARL

ITP is a diagnosis of exclusion. There is no confirmatory test — antiplatelet antibody assays are neither sensitive nor specific enough to be useful. The diagnosis rests on isolated thrombocytopenia with a normal film and no other cause, so drugs, HIV, hepatitis C, SLE, lymphoproliferative disease and pseudothrombocytopenia must all be excluded first.

Treatment

Treat the patient, not the count — observation is appropriate in children and in adults with counts above 30,000 and no bleeding
Corticosteroids are first-line, reducing antibody production and macrophage clearance
Intravenous immunoglobulin for rapid response before surgery or in serious bleeding — it blocks Fc receptors on splenic macrophages, acting within 24–48 hours
Anti-D immunoglobulin in Rh-positive, non-splenectomised patients, by the same mechanism
Splenectomy for refractory cases — it removes both the chief site of destruction and a major source of antibody; effective in about two-thirds
Rituximab and thrombopoietin receptor agonists (romiplostim, eltrombopag) for resistant disease
Platelet transfusion is reserved for life-threatening bleeding, since transfused platelets are destroyed as rapidly as the patient’s own

Applied Aspects

Avoid aspirin, NSAIDs and intramuscular injections, and advise against contact sports while the count is low
In pregnancy maternal IgG crosses the placenta and may cause thrombocytopenia in the neonate, so cord platelets are checked
Evans syndrome — ITP with autoimmune haemolytic anaemia; often refractory and suggests underlying immune dysregulation
Test for HIV and hepatitis C in every adult presenting with apparent ITP, since both commonly present this way and both are treatable
Vaccination before splenectomy against pneumococcus, meningococcus and Haemophilus is mandatory, with lifelong penicillin afterwards

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