Summary
Thrombocytopenia is defined as a low circulating platelet count (<150,000 per microlitre). Platelet life span is normally approximately 5 days, with continual renewal. True thrombocytopenia results from either a reduced production of platelets in the bone marrow, increased clearance, or sequestering of platelets in the spleen.
Epidemiology
The causes of thrombocytopenia are diverse, making epidemiological generalisations difficult. However, immune thrombocytopenic purpura (ITP) is typically an illness of young women. [1] [2] The apparent appearance of ITP in other patient groups should prompt a high index of suspicion for an alternative diagnosis: for example, non-Hodgkin's lymphoma, drug effect, or myelodysplasia.
Investigation
A complete history, physical examination, review of the FBC, and peripheral smear are necessary to narrow down the differential diagnosis of thrombocytopenia. It is important to exclude artifact or pseudothrombocytopenia.
Differential diagnosis
- Common
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- Leukaemia
- Metastatic malignancy
- Lymphoma
- Miliary TB
- Disseminated intravascular coagulation (DIC)
- Post-transfusion
- Haemolysis, elevated liver enzymes, low platelet count (HELLP)
- Cardiopulmonary bypass
- Idiopathic thrombocytopenia (ITP)
- Systemic lupus erythematosus (SLE)
- Rheumatoid arthritis
- Antiphospholipid syndrome
- HIV/AIDS
- Malaria
- Cytomegalovirus (CMV)
- Mononucleosis
- Sepsis
- Heparin-induced thrombocytopenia (HIT)
- Antimalarials, antiepileptic drugs, antibiotics, or chemotherapies
- Alcohol ingestion
- B12 deficiency
- Folate deficiency
- Gestational thrombocytopenia
- Cirrhosis
- Uncommon
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- Multiple myeloma
- Myelofibrosis
- Thrombotic thrombocytopenic purpura (TTP)
- Haemolytic uraemic syndrome (HUS)
- Sarcoidosis
- Cyclic thrombocytopenia
- Wiskott-Aldrich syndrome
- May-Hegglin anomaly
- Bernard-Soulier syndrome
- Hashimoto's thyroiditis
- Aplastic anaemia
- Vaccinations
- Gaucher's disease
- Paroxysmal nocturnal haemoglobinuria (PNH)
- Pseudothrombocytopenia
