View source for WBR0200

 {{WBRQuestion
|QuestionAuthor= {{AO}}
|ExamType=USMLE Step 2 CK
|MainCategory=Internal medicine
|SubCategory=Hematology, Hematology
|MainCategory=Internal medicine
|SubCategory=Hematology, Hematology
|MainCategory=Internal medicine
|SubCategory=Hematology, Hematology
|MainCategory=Internal medicine
|MainCategory=Internal medicine
|SubCategory=Hematology, Hematology
|MainCategory=Internal medicine
|SubCategory=Hematology, Hematology
|MainCategory=Internal medicine
|SubCategory=Hematology, Hematology
|MainCategory=Internal medicine
|SubCategory=Hematology, Hematology
|MainCategory=Internal medicine
|MainCategory=Internal medicine
|SubCategory=Hematology, Hematology
|Prompt=An 85 year old woman with a past medical history of stroke, hypertension and diabetes mellitus is sent to the ER from a nursing home for evaluation of fever and altered mental status.  Vital signs revealed a temperature of 101F, BP: 100/60 mmHg, RR: 22 bpm, HR: 110.  Physical examination revealed an elderly woman not responding to verbal stimuli but moans in response to deep pain.  Ecchymoses are seen on lower extremities.  A foley catheter is present draining cloudy urine. 

Laboratory  studies:
Hgb : 8.4 mg/dl 
WBC: 14,000  
Platelets: 15,000
BUN: 50 
Creatinine: 3.3   
Prothrombin Time: 16.4 (11-15s)
Partial Thromboplastin Time: 60 (25-40s)
LDH level: 478  (45-90 U/L)

Which of the following features would most likely help in identifying the etiology of this patient’s thrombocytopenia?
|Explanation=The patient presents has severe sepsis – fever and cloudy urine.  The cloudy urine indicates that UTI is the possible source of the infection.  Complications of severe sepsis include: multi-organ dysfunction such as hypotension, encephalopathy, disseminated intravascular coagulation (DIC)  and renal insufficiency.  You need to differentiate between DIC and Thrombotic Thrombocytopenic Purpura  (TTP).  
DIC is a consumptive coagulopathy i.e.,  it consumes the entire coagulation factors along with platelets.  Hence, PT and PTT are elevated and fibrinogen is decreased in DIC but not in TTP.  The intravascular thrombi in DIC are fibrin thrombi – the lysis of this lead to increased D-dimer and Fibrin Split Products.  TTP is a consumptive thrombocytopenia, and is composed of platelet thrombi not fibrin – so, D-dimer is usually normal in TTP.  Severe sepsis can resemble TTP.  A full clinical picture should be considered in decision making.  The source of sepsis should be sought and ruled out in suspected cases before making a diagnosis of TTP.


Educational Objective: Complications of severe sepsis include: hypotension, encephalopathy, DIC, e.t.c.  Both disseminated intravascular coagulation and thrombotic thrombocytopenic purpura have similar presentation.  In DIC, there is elevated PT, PTT, D-dimer, and fibrin split products.
|AnswerA=Fragmented red blood cells (Schistocytes)
|AnswerAExp=Incorrect.  The peripheral blood smear shows schistocytes.  This is non- specific.  Schistocytes can occur in any condition that is associated with Microangiopathic Hemolytic Anemia (MAHA).   MAHA can be seen in TTP, HUS, DIC, HELLP syndrome and malignant hypertension.
|AnswerB=Decreased fibrinogen and increased D-dimer
|AnswerBExp=Correct.  The formation of fibrin thrombi in DIC lowers the level of fibrinogen and subsequently increases the products of its degradation i.e. D-dimer and fibrin split products.
|AnswerC=Increased fibrinogen and decreased D-dimer
|AnswerCExp=Incorrect.  This is a distractor.
|AnswerD=Decreased reticulocyte count
|AnswerDExp=Incorrect.  Increased LDH only suggests hemolysis and it is non-specific.
|AnswerE=Elevated LDH
|AnswerEExp=Incorrect.  MAHA is associated with increased reticulocyte count not decreased retic count.
|RightAnswer=B
|WBRKeyword=Thrombotic thrombocytopenic purpura, Disseminated intravascular coagulation, sepsis, severe sepsis
|Approved=Yes
}}