Presentations
Approach to thrombocytopenia
The same eight steps, every presentation: threats first, then the history and exam that discriminate, one honest sentence, a mechanism-grouped differential, and the tests read in order.
Immediate threats
- Thrombotic thrombocytopenic purpura: fragments on the film with thrombocytopenia is plasma exchange tonight
- Heparin-induced thrombocytopenia: a platelet fall 5 to 10 days into heparin with new thrombosis
- Disseminated intravascular coagulation in a sick patient: bleeding and clotting at once
- Intracranial or mucosal bleeding at any count; counts under 10 to 20 without bleeding still change the plan
History that discriminates
- Bleeding: bruises, petechiae, gums, nose, menorrhagia, melena; its tempo
- Drugs, especially heparin, and the timing of every new one; alcohol; recent viral illness or vaccination
- Pregnancy; liver disease; autoimmune disease; HIV and hepatitis C risk
- Fever, confusion, renal symptoms (the microangiopathy pentad, rarely complete)
- Family history and previous counts: a lifelong mild thrombocytopenia is a different problem
Examination
- Petechiae and purpura, wet purpura in the mouth (a marker of bleeding risk), fundal hemorrhage
- Lymphadenopathy, hepatosplenomegaly, stigmata of liver disease
- Signs of thrombosis in a patient on heparin
- Fever and perfusion in the sick patient; neurological examination in the microangiopathy question
Problem representation
An isolated, severe thrombocytopenia in a well young woman with a normal film (immune thrombocytopenia) versus a falling count on day 7 of heparin with a new deep vein thrombosis (heparin-induced) versus fragments, anemia and a rising creatinine in a febrile confused patient (thrombotic microangiopathy).
Differential, by mechanism
Decreased production
- Marrow failure, infiltration, myelodysplasia
- B12 and folate deficiency
- Alcohol
- Chemotherapy and other drugs
- Viral infection
Increased destruction
- Immune thrombocytopenia
- Drug-induced, including heparin
- Thrombotic microangiopathies
- Disseminated intravascular coagulation
- Antiphospholipid syndrome and lupus
Sequestration and dilution
- Hypersplenism, portal hypertension
- Massive transfusion
- Pregnancy (gestational thrombocytopenia, preeclampsia, HELLP)
Artefact
- EDTA-dependent clumping: a citrate tube and the film settle it
Investigations
- Repeat the count and look at the film before anything else: clumps, fragments, giant platelets, blasts
- Coagulation screen with fibrinogen and D-dimer when disseminated intravascular coagulation is possible
- Hemolysis markers and creatinine when fragments appear; a pregnancy test where relevant
- Liver panel and an ultrasound of the spleen; B12 and folate; HIV and hepatitis C; the antibody tests for heparin-induced thrombocytopenia when the score says so
- A marrow when a second line is down, when the film is abnormal, or when the picture is unexplained in an older patient
Interpretation
- Fragments plus thrombocytopenia is a microangiopathy; the ADAMTS13 result comes later and treatment cannot wait for it
- The 4T score turns a suspicion of heparin-induced thrombocytopenia into a decision about stopping the heparin now
- Immune thrombocytopenia is a diagnosis of exclusion: isolated, normal film, nothing else
- Platelet count and bleeding risk correlate poorly; the wet purpura and the mechanism matter more than the number
Next steps
- Stop the suspect drug, above all heparin, on suspicion
- Platelet transfusion is for bleeding and procedures, and is avoided in microangiopathy and heparin-induced disease
- Name the mechanism: production, destruction, sequestration, dilution, artefact
Connected
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