When seeing a patient with thrombocytopenia, there are several ways to approach the differential diagnosis. Click on the links for more detail about the last 2 classification schemes:
1. According to whether or not the thrombocytopenia is real:
- True thrombocytopenia
2. According to whether the thrombocytopenia is congenital or acquired:
- Congenital (familial)
3. According to other changes in the complete blood count:
- Isolated thrombocytopenia – no other significant changes in the complete blood count.
- Thrombocytopenia associated with other abnormalities in blood counts.
- Decreased production:
- Increased consumption/destruction:
- Sequestration – hypersplenism, especially in setting of cirrhosis.
- Emergency department
- Inpatient (new onset)
The most useful of these classifications is clinical context. The classification scheme, which is detailed here, can be conveniently organized as a flow chart:
In our case, we can focus on the differential diagnosis of isolated thrombocytopenia in an outpatient. The most common conditions include:
|Differential diagnosis||History & physical||Labs|
|Pseudothrombocytopenia||In vitro artifact, so patients are asymptomatic.||Peripheral smear to examine for platelet clumping.|
|Immune thrombocytopenia||Bleeding and easy bruising. Symptoms associated with causes of secondary ITP. Signs of mucocutaneous bleeding.||HCV, HIV, H. pylori to rule out secondary causes.|
|Drug-induced thrombocytopenia||History of drug intake, negative in this patient.||No specific testing.|
|Familial (congenital) thrombocytopenia (FT)||Family history of thrombocytopenia and/or bleeding.||Peripheral blood smear to examine for giant platelets (present in some but not all causes of FT.|
|Alcohol abuse||History of heavy drinking, which was negative in this patient.||No specific testing.|
|Cirrhosis||History of liver disease, jaundice, encephalopathy, spider nevi, palmar erythema, splenomegaly. Negative history in this patient.||Transaminases, bilirubin, PT, aPTT, albumin.|
|Antiphospholipid syndrome (APS)||History of thrombosis (or incase of women, pregnancy loss), livedo reticularis and other cutaneous manifestations, symptoms associated with secondary causes such as systemic lupus erythematosus. Negative history in this patient.||Thrombocytopenia is usually mild (platelet count 50-150 × 109/L) and asymptomatic. Severe thrombocytopenia is extremely rare outside the context of APS-associated thrombotic microangiopathy.|
At this point, we only have a history. We have not yet done a physical exam, nor have we ordered any lab tests. Based on what we know so far: