A term baby girl born in an Abu Dhabi hospital is well but develops a few petechiae on day 3. Her platelet count was 96 × 10^9/L in cord blood and is now 28 × 10^9/L; the MPV is normal, and the film shows normal-sized platelets without clumps and normal neutrophils. Hb 172 g/L (17.2 g/dL), WBC 13.5 × 10^9/L, CRP normal, PT and APTT normal for age. Her mother was diagnosed with immune thrombocytopenia at age 25, after normal counts in her teens, and had a platelet count of 61 × 10^9/L at delivery. What is the most likely cause of the baby's thrombocytopenia?

Maternal antiplatelet autoantibody crossing the placenta

Fetal and neonatal alloimmune thrombocytopenia

Inherited MYH9-related macrothrombocytopenia

Neonatal sepsis with consumption of platelets

A 52-year-old woman who takes quinine now and then for leg cramps takes a dose after a month off it. Within hours she has widespread petechiae and a platelet count of 4 × 10^9/L; last week it was 260 × 10^9/L. The film shows no clumps or schistocytes. What is the most likely cause?

Drug-dependent platelet antibodies

Thrombotic thrombocytopenic purpura

Heparin-induced thrombocytopenia

A 7-year-old has had repeated episodes of thrombocytopenia with schistocytes and a raised LD since infancy, each settling after plasma infusion. ADAMTS13 activity is below 5% (reference above 50%), and no ADAMTS13 inhibitor or anti-ADAMTS13 IgG is found. Both parents have activity near 50%. The most likely diagnosis is:

Congenital TTP from ADAMTS13 gene variants

Atypical HUS from complement dysregulation

Immune TTP with a low-titre inhibitor

Platelet disorders: quantitative and qualitative

14 DOH Abu Dhabi (HAAD) lab licensing practice questions on Platelet disorders: quantitative and qualitative, part of Hematology. The first 14 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
A term baby girl born in an Abu Dhabi hospital is well but develops a few petechiae on day 3. Her platelet count was 96 × 10^9/L in cord blood and is now 28 × 10^9/L; the MPV is normal, and the film shows normal-sized platelets without clumps and normal neutrophils. Hb 172 g/L (17.2 g/dL), WBC 13.5 × 10^9/L, CRP normal, PT and APTT normal for age. Her mother was diagnosed with immune thrombocytopenia at age 25, after normal counts in her teens, and had a platelet count of 61 × 10^9/L at delivery. What is the most likely cause of the baby's thrombocytopenia?
1. AFetal and neonatal alloimmune thrombocytopenia
2. BInherited MYH9-related macrothrombocytopenia
3. CMaternal antiplatelet autoantibody crossing the placenta
4. DNeonatal sepsis with consumption of platelets
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Answer: C · Maternal antiplatelet autoantibody crossing the placenta
The mother's own count is low from ITP, so her IgG autoantibody, which binds antigens on everyone's platelets, has crossed the placenta and is clearing the baby's platelets. The neonatal count typically falls after birth and reaches its lowest point at about 2 to 5 days, as here, so counts are followed through the first week. In FNAIT the mother makes an alloantibody against a fetal platelet antigen such as HPA-1a, and her own platelet count is normal. A well baby with a normal CRP and normal clotting times does not fit sepsis with consumption, and normal-sized platelets without neutrophil inclusions, in a baby whose mother's thrombocytopenia was acquired, argue against an MYH9 disorder.
- A: In FNAIT the mother's own platelet count is normal.
- B: MYH9 disorders give giant platelets and neutrophil inclusions, not seen here.
- D: The baby is well, with a normal CRP and normal clotting times.
Question 2 · Medium
A 26-year-old with no bleeding history has an impedance platelet count of 48 × 10^9/L. The film shows many giant platelets and pale blue, spindle-shaped inclusions in the neutrophils. The most likely diagnosis is:
1. AImmune thrombocytopenia
2. BBernard-Soulier syndrome
3. CMYH9-related disorder
4. DGray platelet syndrome
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Answer: C · MYH9-related disorder
MYH9-related disorders, which include the May-Hegglin anomaly, combine giant platelets, mild to moderate thrombocytopenia and Döhle-like inclusions of abnormal myosin heavy chain in neutrophils. Bleeding is usually mild, and some patients later develop hearing loss, cataracts or kidney disease. Impedance counters often miss giant platelets, so the true count is higher than reported. The neutrophil inclusions are the clue that separates this from Bernard-Soulier syndrome and ITP.
- A: ITP can show large platelets but no inclusions in neutrophils.
- B: Bernard-Soulier syndrome has giant platelets with normal neutrophils and a clear bleeding tendency.
- D: Gray platelet syndrome has pale, agranular platelets but no neutrophil inclusions.
Question 3 · Easy
Gray platelet syndrome, in which platelets look large and pale on a Romanowsky-stained film, is a deficiency of platelet:
1. AGlycoprotein Ib-IX-V
2. BGlycoprotein IIb/IIIa
3. CAlpha granules
4. DDense granules
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Answer: C · Alpha granules
Alpha granules hold proteins such as fibrinogen, von Willebrand factor, platelet factor 4 and growth factors, and they give platelets their purple granular look. In gray platelet syndrome these granules are absent or empty, so the large platelets stain gray-blue and look agranular. Most cases are due to NBEAL2 variants, and marrow fibrosis may develop over time. Electron microscopy confirms the missing alpha granules.
- A: Lack of GPIb-IX-V is Bernard-Soulier syndrome.
- B: Lack of GPIIb/IIIa is Glanzmann thrombasthenia.
- D: Dense granule deficiency leaves platelets looking normal on a film.
Question 4 · Hard
A 52-year-old woman who takes quinine now and then for leg cramps takes a dose after a month off it. Within hours she has widespread petechiae and a platelet count of 4 × 10^9/L; last week it was 260 × 10^9/L. The film shows no clumps or schistocytes. What is the most likely cause?
1. ADrug-dependent platelet antibodies
2. BThrombotic thrombocytopenic purpura
3. CHeparin-induced thrombocytopenia
4. DNewly presenting primary ITP
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Answer: A · Drug-dependent platelet antibodies
Quinine is a classic cause of drug-induced immune thrombocytopenia, in which antibodies bind platelet glycoproteins only when the drug is present. A first course causes a fall after about 1-2 weeks, but in a person already sensitized the count can drop within hours of the next dose, often below 20 × 10^9/L. The count recovers within days of stopping the drug. Quinine is also present in tonic water, so a careful drug and drink history is part of the workup.
- B: TTP shows schistocytes and hemolysis, which are absent here.
- C: HIT needs heparin exposure and rarely drops the count below 20 × 10^9/L.
- D: Primary ITP does not usually fall from normal to 4 × 10^9/L within hours of a drug dose.
Question 5 · Hard
A 7-year-old has had repeated episodes of thrombocytopenia with schistocytes and a raised LD since infancy, each settling after plasma infusion. ADAMTS13 activity is below 5% (reference above 50%), and no ADAMTS13 inhibitor or anti-ADAMTS13 IgG is found. Both parents have activity near 50%. The most likely diagnosis is:
1. ACongenital TTP from ADAMTS13 gene variants
2. BAtypical HUS from complement dysregulation
3. CImmune TTP with a low-titre inhibitor
4. DShiga toxin-associated HUS
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Answer: A · Congenital TTP from ADAMTS13 gene variants
Congenital TTP (Upshaw-Schulman syndrome) is caused by variants in both copies of the ADAMTS13 gene, so the enzyme is severely lacking without any antibody. Parents who each carry one variant have about half-normal activity and no symptoms. Episodes respond to plasma infusion, which supplies the missing enzyme, whereas immune TTP needs plasma exchange and immunosuppression. In atypical and Shiga toxin HUS, ADAMTS13 activity is not severely reduced.
- B: Atypical HUS from complement defects leaves ADAMTS13 activity above 10%.
- C: Immune TTP shows an inhibitor or anti-ADAMTS13 IgG and rarely starts in infancy.
- D: Shiga toxin HUS follows bloody diarrhea and has no severe ADAMTS13 deficiency.
Question 6 · Medium
A healthy woman at 37 weeks of pregnancy has a platelet count of 118 × 10^9/L (reference 150-400 × 10^9/L); it was normal before pregnancy. Her blood pressure, liver enzymes and film are normal. What is the most likely cause?
1. AGestational thrombocytopenia
2. BThrombotic thrombocytopenic purpura
3. CImmune thrombocytopenia
4. DHELLP syndrome
Answer and explanation in LearnFree account
Question 7 · Easy
Wiskott-Aldrich syndrome causes thrombocytopenia with platelets that are typically:
1. ASmaller than normal
2. BNormal in size and granules
3. CNormal in size but agranular
4. DLarger than normal
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Question 8 · Hard
A 41-year-old woman with heavy periods has Hb 89 g/L (8.9 g/dL), MCV 66 fL, ferritin 3 µg/L (reference 15-150 µg/L), WBC 7.2 × 10^9/L and platelets 690 × 10^9/L (reference 150-400 × 10^9/L). CRP is normal, and the film confirms many normal-looking platelets. The high platelet count is most likely:
1. AReactive, from iron deficiency
2. BChronic myeloid leukemia
3. CEssential thrombocythemia
4. DPrimary myelofibrosis
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Question 9 · Medium
In thrombotic thrombocytopenic purpura (TTP), the platelet count falls mainly because platelets are used up in:
1. AAntibody coating and splenic removal
2. BPooling within an enlarged spleen
3. CFibrin-rich clots formed by thrombin
4. DVWF-rich microthrombi in small vessels
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Question 10 · Easy
A 4-year-old has sudden petechiae and a platelet count of 9 × 10^9/L three weeks after a viral illness. The rest of the CBC and the film are normal. What is the usual course of this condition?
1. ARecovery within months in most children
2. BLifelong need for platelet transfusions
3. CProgression to acute leukemia within a year
4. DChronic ITP lasting years in most children
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Question 11 · Hard
A 17-year-old with oculocutaneous albinism, nystagmus and lifelong nosebleeds has a normal platelet count and size and normal von Willebrand studies. Aggregation shows only a primary wave with ADP and epinephrine, and ATP release is markedly reduced. Which test would best confirm the diagnosis?
1. AFlow cytometry showing low CD42b
2. BElectron microscopy showing absent dense granules
3. CFlow cytometry showing low CD41 and CD61
4. DADAMTS13 activity below 10%
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Question 12 · Hard
A 29-year-old woman has fatigue and bruising. Results: Hb 78 g/L (7.8 g/dL), reticulocytes 9%, platelets 14 × 10^9/L, many spherocytes and no schistocytes, DAT positive for IgG, PT and APTT normal. The most likely diagnosis is:
1. AEvans syndrome
2. BThrombotic thrombocytopenic purpura
3. CDisseminated intravascular coagulation
4. DHereditary spherocytosis
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Question 13 · Medium
A healthy woman's platelet count is low on every EDTA sample, the film shows platelet clumps, and a citrate sample gives a normal count. What causes the clumping?
1. AHeparin-dependent antibodies to platelet factor 4
2. BAntibodies to a GPIIb/IIIa site exposed by EDTA
3. CPlatelet activation during a slow, difficult draw
4. DCold antibodies binding to her red cells
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Question 14 · Medium
Which set of findings best fits primary immune thrombocytopenia (ITP) in an adult?
1. AIsolated low platelets, some large, with an otherwise normal film
2. BLow platelets with a long PT and APTT and low fibrinogen
3. CLow platelets with circulating blasts and neutropenia
4. DLow platelets with schistocytes and a raised LD
Answer and explanation in LearnFree account

Platelet disorders: quantitative and qualitative

A 26-year-old with no bleeding history has an impedance platelet count of 48 × 10^9/L. The film shows many giant platelets and pale blue, spindle-shaped inclusions in the neutrophils. The most likely diagnosis is:

Gray platelet syndrome, in which platelets look large and pale on a Romanowsky-stained film, is a deficiency of platelet:

A 52-year-old woman who takes quinine now and then for leg cramps takes a dose after a month off it. Within hours she has widespread petechiae and a platelet count of 4 × 10^9/L; last week it was 260 × 10^9/L. The film shows no clumps or schistocytes. What is the most likely cause?

A healthy woman at 37 weeks of pregnancy has a platelet count of 118 × 10^9/L (reference 150-400 × 10^9/L); it was normal before pregnancy. Her blood pressure, liver enzymes and film are normal. What is the most likely cause?

Wiskott-Aldrich syndrome causes thrombocytopenia with platelets that are typically:

In thrombotic thrombocytopenic purpura (TTP), the platelet count falls mainly because platelets are used up in:

A 4-year-old has sudden petechiae and a platelet count of 9 × 10^9/L three weeks after a viral illness. The rest of the CBC and the film are normal. What is the usual course of this condition?

A 17-year-old with oculocutaneous albinism, nystagmus and lifelong nosebleeds has a normal platelet count and size and normal von Willebrand studies. Aggregation shows only a primary wave with ADP and epinephrine, and ATP release is markedly reduced. Which test would best confirm the diagnosis?

A 29-year-old woman has fatigue and bruising. Results: Hb 78 g/L (7.8 g/dL), reticulocytes 9%, platelets 14 × 10^9/L, many spherocytes and no schistocytes, DAT positive for IgG, PT and APTT normal. The most likely diagnosis is:

A healthy woman's platelet count is low on every EDTA sample, the film shows platelet clumps, and a citrate sample gives a normal count. What causes the clumping?

Which set of findings best fits primary immune thrombocytopenia (ITP) in an adult?