Platelet disorders: Pathology review

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Platelet disorders: Pathology review

Hematological system

Hematological system

Hematological system

Hematological system


Platelet disorders: Pathology review

USMLE® Step 1 questions

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USMLE® Step 1 style questions USMLE

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A 9-year-old boy is brought to the emergency department by his parents due to prolonged bleeding following a tooth extraction earlier in the day. Past medical history is noncontributory. Temperature is 37.5°C (99.5°F), pulse is 88/min, respirations are 14/min, and blood pressure is 112/62 mmHg. Physical exam shows gingival bleeding and petechiae. Laboratory testing is obtained, and the results are shown below.  
Laboratory value  Result
 Hemoglobin  12 g/dL 
 Hematocrit  40% 
 Platelet count  95,000/mm3  
 Leukocyte count  9,000/mm3  
Coagulation studies  
 Prothrombin time (PT)  12 seconds 
 Activated partial thromboplastin time (aPTT)  29 seconds 
 Bleeding time*  15 minutes 
*Reference Range: 2-7 minutes  

Which of the following conditions is the patient at greatest risk of developing?   


At the family medicine center, a mother came in with her 5 year old child, Alana.

Several days ago, Alana developed bloody diarrhea after eating undercooked ground beef and her mother noticed her face was pale and she only urinated once in the past 12 hours.

Next to her, there’s a 30 year old person named Danika, who came in complaining of increased bruising for the past several months.

She has no other symptoms and physical examination shows multiple ecchymoses on the extremities.

Both Alana and Danika are suffering from a hemostasis disorder.

Hemostasis disorders, also known as bleeding disorders, can be broadly divided into three groups.

The first includes problems with primary hemostasis, which is when there’s a problem forming the initial platelet plug, and so, they’re referred to as platelet disorders.

Now, the second group includes problems with secondary hemostasis, which is making a strong fibrin clot through activation of the intrinsic, extrinsic and common coagulation pathways, and are also known as coagulation disorders.

And the last group includes disorders that affect both primary and secondary hemostasis and are known as mixed platelet and coagulation disorders.

For this video, let’s focus on the platelet disorders.

These can be further subdivided into two categories. In the first category, there’s thrombocytopenia, which is defined as a platelet count below 150,000 per microliter, with the normal range being between 150,000 and 450,000.

Thrombocytopenia can be caused by increased platelet destruction, which can be immune-mediated, like in heparin induced thrombocytopenia, or HIT, and immune thrombocytopenic purpura, or ITP.

Other cases can be non-immune mediated, like thrombotic thrombocytopenic purpura, or TTP, and hemolytic-uremic syndrome, or HUS.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Williams Hematology, Eighth Edition" McGraw-Hill Education / Medical (2010)
  6. "Heparin induced thrombocytopenia: diagnosis and management update" Postgraduate Medical Journal (2007)
  7. "The management of heparin-induced thrombocytopenia" British Journal of Haematology (2006)
  8. "Management of Adult Idiopathic Thrombocytopenic Purpura" Annual Review of Medicine (2005)
  9. "ABC of clinical haematology: Platelet disorders" BMJ (1997)
  10. "Syndromes of Thrombotic Microangiopathy" Medical Clinics of North America (2017)
  11. "Thrombotic Microangiopathies" New England Journal of Medicine (2002)
  12. "Hemolytic Uremic Syndrome: New Developments in Pathogenesis and Treatment" International Journal of Nephrology (2011)
  13. "Glanzmann thrombasthenia: a review of ITGA2B and ITGB3 defects with emphasis on variants, phenotypic variability, and mouse models" Blood (2011)
  14. "Amelioration of the macrothrombocytopenia associated with the murine Bernard-Soulier syndrome" Blood (2002)
  15. "Platelet Dysfunction in Renal Failure" Seminars in Thrombosis and Hemostasis (2004)

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