Question 11.3

A 70-year-old man presents with a seven-day history of recurrent epistaxis, bruising and increasing haemoptysis. He has no significant past medical history other than a TIA for which he takes Aspirin. He does not have any epistaxis at present. His INR and APTT are normal.

Hb	96 g/L *	(135-175)
RBC	3.32 x 10¹² /L*	(4.50-6.00)
PCV	0.29 *	(0.40-0.50)
MCV	86.7 fl	(80.0-98.0)
MCH	28.9 pg	(27.0-33.0)
MCHC	333g/L	(315-355)
Platelets	2 x 10⁹/L*	(150-400)
Immature Platelet Forms	17%*	(1.1-6.1)
Reticulocytes	0.6%	(0.5-2.0)
White Cell Count	8.82 x 10⁹/L	(4.0-11.0)

i. List 6 potential aetiologies for the above blood picture in this patient.

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College Answer

Decreased platelet production
- Marrow failure (eg aplastic anaemia, myelodysplasia)
- Exposure to drugs (eg quinine)
- Marrow infiltration (eg neoplastic)
- Nutritional
Increased platelet destruction
- Immune thrombocytopenic purpura (incl idiopathic, CT disease, lymphoproliferative disease, medications, infection (eg HIV, Hep C)).
- Thrombotic microangiopathy
- Drug-induced
Increased sequestration of platelets
- Hypersplenism

Discussion

This question favours the candidate who can generate a large number of differentials. Specifically, the differentials are for the question "what causes peripheral platelet breakdown". Because there is a large proportion of immature forms, one can presume that the bone marrow is functioning normally. However, the college offers a few differentials which involve bone marrow failure.

Furthermore, thrombotic microangiopathy is brought up, which would also cause a haemolysis of red cells. (well, the man is a little anaemia, but he has been having epistaxis for 7 days so its far from surprising)

So: I give up.

Here is a link to an article with a diagnostic approach to thrombocytopenia. The well-resourced candidate will also draw on UpToDate: Approach to the adult patient with thrombocytopenia.

Causes of Thrombocytopenia
Decreased platelet production Bone marrow suppression Alcohol toxicity Chemotherapy Congential causes, eg. Fanconi anaemia Myelofibrosis or aplastic anaemia Neoplasm, eg. leukaemia or lymphoma Viral infection, eg. HIV, EBV, Hep C, parvovirus, mumps, rubella, varicella... Nutritional deficiency: B12 and folate deficiency Liver disease - decreased production of thrombopoietin (TPO)	Increased platelet destruction SLE ITP DIC Drugs: Quinine Heparin Valproate Post-transfusion thrombocytopenia Microangiopathic haemolytic anaemia Thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP-HUS) Antiphospholipid syndrome HELLP syndrome in pregnancy Physical destruction in the cardiopulmonary bypass apparatus or circuit
Pseudothrombocytopenia The sample was improperly anticoagulated, and there is platelet clumping on microscopy of the blood film. Send a citrated tube instead- often the EDTA is to blame. Abciximab can cause this, as it is an antibody to the GP IIb/IIIa receptor.	Dilution of platelets Massive transfusion Massive fluid resuscitation Sequestration Hypersplenism Accessory spleens or splenunculi Hepatic sequestration Extremes of hypothermia

References

Stasi, Roberto. "How to approach thrombocytopenia." ASH Education Program Book 2012.1 (2012): 191-197.

UpToDate: Approach to the adult patient with thrombocytopenia.

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