Thrombocytopenia is a platelet count that is under the normal lower limit (150 x 109/L). Platelets otherwise known as thrombocytes are located in the blood alongside red blood cells (erythrocytes), white blood cells (leukocytes) and plasma. The megakaryocytes are large cells that develop in bone marrow and undergo fragmentation to produce platelets. Platelets have no nucleus, instead they have granules where proteins are located to assist with its function. The function of platelets is to help with blood clotting. Platelets ‘stick’ together to stop the blood flowing from damaged blood vessels.
This can be due to a number of causes:
1) Platelet function abnormalities:
Thrombocytopathy – this can be due to defects such as genetics (inherited) and acquired of platelet function. Examples include Megakaryocytic hypoplasia – This is where megakaryocytes are underdeveloped,
Wiskott-Aldrich syndrome (WAS) – This is an X-linked recessive disease.
2) Low platelet production.
This can be due to disorders of bone marrow due to a number of reasons:
Cancer: myeloma, leukaemia, lymphoma – It can also be caused by chemotherapy!
Infection – mainly viruses such as HIV, hepatitis, Epstein-Barr, Cytomegalovirus, Herpes Simplex, Varicella-Zoster.
3) Low Platelet survival. This can be caused by:
This includes rheumatoid arthiritis, post-transfusion thrombocytopenic purpura (PTTP), neonatal alloimmune thrombocytopenia (NAIT).
PTTP: This is where antigens on transfused platelets, destruct transfused platelets as well as the platelets of the patients. This normally occurs 10 days after transfusion and can last few weeks.
NAIT: This is where the mother makes antibodies that are against the foetus (baby’s) platelets with paternal antigens. This can lead to severe neonatal thrombocytopenia.
Medications such as ibuprofen, vancomycin, heparin can cause thrombocytopenia.
In some pregnancies, HELLP syndrome can occur and stands for:
· EL (elevated liver) enzymes.
· LP (low platelet) count.
4) Dilutional thrombocytopenia
This is caused by transfusion of high volumes of blood that may have dead platelets.
Below is a diagnostic approach I created for thrombocytopenia and what tests recommended:
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