Heparin-induced thrombocytopenia differential diagnosis

Heparin-induced thrombocytopenia
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [2] Shyam Patel [3]

Overview

Heparin-induced thrombocytopenia is diagnosed when the platelet count falls by > 50% typically after 5-10 days of heparin therapy. It should be differentiated by other causes of thrombocytopenia like hemolytic uremic syndrome, Thrombotic thrombocytopenia and others.

Differential diagnosis

The table below summarizes the different findings between HIT and other diseases in the differential diagnosis:

Characteristic/Parameter	HIT	DIC	HUS	Atypical HUS	ITP	PTP	SLE
Symptoms	Bleeding, thrombosis, skin necrosis	Bleeding, thrombosis, petechiae, sepsis	Renal failure, hematuria, bleeding, microangiopathic hemolytic anemia	Renal failure, hematuria, bleeding, microangiopathic hemolytic anemia	Petechiae, bleeding, other autoimmune diseases	Petechiae, purpura, ecchymoses	Bleeding, photosensitivity, arthritis, malar rash, discoid rash, renal failure, seizures, psychosis
Platelet count	Low but usually more than 20000 per microliter	Low	Low	Low	Low; can be as low as 10000 per microliter	Low; can be less than 10000 per microliter; sudden onset after transfusion	Variable; usually low
PT and PTT	Normal	Elevated	Normal	Normal	Normal	Normal	Usually normal
Etiology	Heparin exposure	Sepsis, delivery of fetus, acute promyelocytic leukemia, other malignancy	E.coli strain O157:H7; Shiga-like toxin	Dysregulation of complement activation; mutation in complement factor H	Idiopathic; can be secondary to chronic lymphocytic leukemia, HIV, viral hepatitis, H. pylori	Exposure to transfused products	Autoimmunity with development of antibodies to DNA
Drug-related	Yes, always	Possible	No	No	Yes	No; transfusion-related	Possible; drug-induced lupus can be caused by medications like hydralazine or isoniazid
Bleeding	Possible	Usually	Usually	Usually	Yes; spontaneous bleeding if platelet count < 10000 per microliter	Yes; spontaneous bleeding if platelet count < 10000 per microliter	Rare

Table legend: HIT, heparin-induced thrombocytopenia; DIC, disseminated intravascular coagulation; HUS, hemolytic-uremic syndrome; ITP, immune thrombocytopenia purpura; PTP, post-transfusion purpura; SLE, systemic lupus erythematosis