As with a number of haematological emergencies, the first sign of a major problem is through a grossly abnormal full blood count. In this case the biomedical scientists made a blood film and confirmed the thrombocytopenia was true. The film was passed onto the haematology registrar who made a morphological and clinical comment. The patient’s main symptom was lethargy and this was why a blood count was done. As there were no other abnormalities in the film apart from hypochromia a diagnosis of ITP was made and the patient was started on steroids. Concomitant iron deficiency due to menorrhagia was suspected and iron replacement was initiated. A bone marrow aspirate or trephine biopsy was not performed. A week later her platelet count had increased and after a further week her steroids were weaned.
The differential diagnosis of a low platelet count is wide. The main ones are:
- Reduced production: Bone marrow failure (MDS, aplastic anaemia), marrow infiltration (leukaemia, lymphoma, other malignancies), toxins (alcohol, drugs e.g. chloramphenicol, chemo), megaloblastic anaemia (B12/folate deficiency), viral infection (HIV, Hep C, CMV, VZV, EBV, Dengue), liver failure
- Reduced survival: Immune mediated (ITP, HIT, drugs (penicillin, antiepileptics), HIV, autoimmune diseases (rheumatoid, SLE, antiphospholipid syndrome), sarcoid, NAIT, post transfusion purpura), non-immune (DIC, sepsis, TTP, malaria, HUS, endocarditis, pregnancy-related (HELLP, pre-eclampsia), thrombosis, metallic valve, intra-aortic balloon pump), hypersplenism (sickle, alcohol, liver failure, malaria, lymphoma, EBV/viral, Felty’s syndrome, myelofibrosis, amyloid).
- Dilutional – e.g. major trauma
- Pseudo – i.e. platelet clumping
- Hereditary – Alport’s syndrome, Wiskott Aldrich Syndrome, May Hegglin Anomaly, Fanconi’s, thrombocytopenia absent radius syndrome
Investigations are targeted by the history and examination whist bearing in mind the above causes.
Investigations – depending on history and examination
- FBC with film
- Biochemistry: U&E, LFT, Ca, LDH
- Viral: HIV, Hep C, EBV, CMV
- Cultures if septic
- Autoimmune screen
- Clotting screen, lupus anticoagulant
- Group and save
- Bone marrow aspirate and trephine biopsy
- Pregnancy test
Immune Thrombocytopenic Purpura
This disease is different in adults and children and the disease in adults is discussed here.
This is an acquired autoimmune disorder; the full aetiology of which is poorly understood. It may occur following viral infection, in the context of autoimmune disorder or in a lymphoproliferative disease. Many patients complain of lethargy, bruising or a petechial rash. Major bleeding is rarely a complication.
There is no diagnostic test and the diagnosis is often one of exclusion. Investigations are listed below
The use of bone marrow aspirates is varied. Guidelines state: “Bone marrow examination may be informative in patients older than 60 years of age, in those with systemic symptoms or abnormal signs, or in some cases in which splenectomy is considered”. If another diagnosis is considered e.g. lymphoproliferative disorder this will be useful. In post cases the marrow will be normal with plenty of megakaryocytes indicating peripheral destruction of platelets. A megakaryocyte is seen below:
Treatment is not usually indicated in platelet counts above 50. Corticosteroids – usually 1mg/kg of prednisolone is the standard first line treatment. Advice re side effects is given and a proton pump inhibitor is prescribed. Osteoporosis prevention may be needed if steroids are given long-term. Pulsed dexamethasone is also given. If steroids cannot be weaned a sparing agent such as azathioprin can be used. Second and third line treatments include rituximab, splenectomy, thrombopoietin agonists.
In emergencies intravenous immunoglobulin, platelet transfusions, supportive measures, high dose steroids and tranexamic acid can be used.
For more information
This ITP guideline in Blood covers most of the basics in ITP: http://bloodjournal.hematologylibrary.org/content/115/2/168.full.pdf