Author: Tay Xue Chao Brian Diaz / Editor: Sarah Edwards / Codes: HP1, HP2, ObC17, SLO1 / Published: 05/05/2021
A 42-year-old lady who is 35 weeks pregnant is brought into your department by her husband. He reports that she started having diarrhoea about 7 days ago, but has now also developed confusion, fever, and widespread bruises despite the absence of trauma.
On general examination, she appears unwell.
- Airway: Patient.
- Breathing: Equal and good air entry bilaterally. Respiratory rate 25. Oxygen saturations on room air 96%.
- Circulation: Heart sounds normal. Capillary refill <2 seconds. Heart rate 120. Blood pressure 130/80.
- Disability: GCS 14 as she is mildly confused and does not know where she is. She does not have any neck stiffness, photophobia, or any other signs of meningeal irritation. Formal neurological examination reveals no abnormalities.
- Temperature: 38 Degrees Celsius.
- Exposure: Her abdomen is soft and is in keeping with the pregnancy.
There is a widespread purpuric rash and ecchymosis. The picture below is of her legs.

Bloods and cultures were taken at triage.
Laboratory results:
Haemoglobin: 8 g/dL
White cell count: 12 x 10^9/L
Neutrophils: 7 x 10^9/L
Platelets: 55 x 10^9/L
Prothrombin time (PT): 14 seconds (10-14 seconds)
Activated partial thromboplastin time (APTT): 35 seconds (24-37 seconds)
Fibrinogen: 3.10 g/L (1.50-4.50 g/L)
D-dimer: 180 ng/mL (<300 ng/mL)
Na+: 140 mmol/L
K+: 4.5 mmol/L
Urea: 26 mmol/L
Creatinine: 320 umol/L
pH: 7.25
Lactate: 4.3
Glucose: 8 mmol/L
Urine dip shows 3+ protein and 1+ RBC. Leukocytes and nitrites are negative.
The laboratory has taken the liberty of doing a peripheral blood smear. Schistocytes are present.

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Question 1 of 3
1. Question
Considering this case as a whole, what is the most likely diagnosis regarding the cause of the rash?
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Question 2 of 3
2. Question
You are extremely worried about this patient and request that ITU review her as part of your initial management. You also make a referral to the obstetric registrar.
The ITU registrar reviews the patient and is just as concerned as you. After a quick chat with her consultant, she prepares a bed and whisks the patient over to ITU. She is happy for the obstetric registrar to review the patient there.
Which one of the following treatment strategies is not appropriate for this patient?
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Question 3 of 3
3. Question
A few days later, you are reviewing the patient’s progress at a workstation with some interested colleagues and are pleased to find that the patient is improving and is about to be stepped down soon.
You note that the patient has had both an ADAMTS13 activity assay and anti ADAMTS13 antibody levels done while in ITU. ADAMTS13 activity is <10% and the antibody levels are high – which indicates that the TTP is autoimmune and acquired as opposed to hereditary (Upshaw-Schulman syndrome). You proceed to impress your colleagues by informing them that the pathogenesis of TTP involves a deficiency in a protease synthesised in the liver known as ADAMTS13 (A Disintegrin And Metalloproteinase with a ThromboSpondin type 1 motif, member 13).1,2
You teach them that ADAMTS13 is involved in cleaving von Willebrand factor (vWF) – a plasma glycoprotein that binds platelets at sites of vascular injury. Reduced ADAMTS13 activity therefore means that there is increased vWF activity specifically due to the persistence of ultra-large von Willebrand factor multimers (ULVWF). This in turn leads to increased platelet aggregation (causing thrombosis) and therefore reduced platelets in the circulation (thrombocytopenia).1,2
The ADAMTS13 deficiency also definitively differentiates TTP from HUS since the typical form of HUS is caused by Shiga toxin and the atypical form is complement-mediated.
As part of your informal lesson, you ask them to guess the mortality rate of TTP if left undiagnosed and untreated. What is it?
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Module Content
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10 responses
Thank you. Very informative module
This case remind me the importance of defferintiateding purporic rash in ED, very appreciated effort
Great learning
Thank you
A rare but very well explained and differentiated from other conditions.
Thanks RCEM for updating.
Good review
interesting
good presentation
excellent
Excellent learning module
excellant case