Deck XVI Flashcards Preview

USMLE World Missed Questions > Deck XVI > Flashcards

Flashcards in Deck XVI Deck (30):
1

What is the pathophysiology associated with G6PD deficiency?

An X-linked erythrocyte enzyme deficiency of the hexose monophosphate pathway. NADPH produced in RBCs is low which impairs glutathione- mediated inactivation of free radicals. This induces hemolytic episodes as induced by infections, medications, and other oxidants.

2

What type of anemia is implicated by schistocytes (fragmented RBCs) in a peripheral smear?

Microangiopathic hemolytic anemia

3

Name five causes of microangiopathic hemolytic anemia.

HUS, TTP, DIC, malignant hypertension, metastatic carcinoma.

4

What is the the underlying pathophysiology of hemolytic uremic syndrome?

Endothelial cell injury causes isolated activation of platelets and formation of microthrombi. RBCs are damaged when passing through mucrovascular channels and appear as schistocytes. The coagulation system is not activated thus PT and PTT are normal

5

What is the characteristic pentad of symptoms in HUS and TTP?

Fever, neurologic manifestations, renal failure, thrombocytopenia, microangiopathic hemolytic anemia

6

What are the principle epidemiological differences between HUS and TTP?

HUS occurs primarily in children and has renal involvement; TTP occurs most often in adults with predominant neurological symptoms. Fever, thrombocytopenia, microangiopathic hemolytic anemia are common in both conditions.

7

What is the treatment for HUS and TTP?

Emergent plasmapheresis.

8

What are metalloproteinases?

Zn containing enzymes that degrade extracellular matrix. They participate in normal tissue remodeling and in tumor invasion through the basement membrane and connective tissue.

9

What is Immune thrombocytopenic purpura (ITP)?

An autoimmune disease characterized by the immune destruction of platelets by anti-platelet antibodies. In children it is typically acute and self limited while in adults it is often insidious and chronic. Tx is immunosuppression (steroids).

10

What symptoms are associated with immune thrombocytopenic purpura?

Ecchymoses, petechiae, mucosal bleeding without signs and symptoms of TTP/HUS, pancytopenia, marrow failure or splenomegaly.

11

What condition is indicated by red blood cells without central pallor?

Spherocytes. Indicate spherocytosis.

12

What red cell index is most specific for spherocytosis?

Elevated mean corpuscular hemoglobin concentration (MCHC).

13

What differentiates the presentation of CML from leukemoid reaction?

Both cause elevation of WBCs but neutrophil alkaline phosphatase level is elevated or normal in a leukamoid reaction but is decreased in CML.

14

What is the difference in lab values between AML and CML?

In AML, myeloblasts are elevated; in CML, there are few blasts.

15

What is the most important criteria for determining cancer prognosis?

Tumor stage (extent of tumor expansion)

16

What is considered first line treatment for DVTs in pregnant women?

Heparin.

17

What is the underlying pathology associated with mealoblastosis?

A defect in DNA synthesis. In chronic alcoholics this can result from a nutritional deficiency of folate which impairs synthesis of purine and pyrimidine bases.

18

What do blast cells look like on peripheral smear?

Very large nucleated cells with scant cytoplasm.

19

What is required for diagnosis of AML?

Greater or equal to 20% myeloblasts in the peripheral blood or marrow.

20

What is a complication associated with massive transfusion of packed red blood cells (i.e. more than 5-6 L of blood)?

Chelation of serum calcium (and magnesium), causing hypocalcemia and parasthesias. This is caused by elevated plasma levels of citrate, a substance added to stored blood.

21

In a patient with an intrinsic pathway clotting defect, administration of what agent will induce blood clotting?

Thrombin.

22

What lab findings are characteristic of HUS?

Decreased RBC count, hematocrit, and platelet count, increased bleeding time, LDH, BUN, and creatinine.

23

What is Polycythemia Vera?

A clonal myeloproliferative disease of pluripotent hematopoietic stem cells. JAK2 mutation renders hematopoietic stem cells more sensitive to growth factors.

24

How does polycythemia vera present?

With increased RBC mass, increased plasma volume, low erythropoietin levels; elevated WBC count, thrombotic events (blood hyperviscosity), peptic ulceration, pruritus, gouty arthritis.

25

What are common physical exam findings in a patient with polycythemia vera?

Plethoric, ruddy face and splenomeagly.

26

What is the treatment for polycythemia vera?

Serial phlebotomy to keep hematocrit < 45%.

27

What may cause increased hematocrit in patients with obstructive sleep apnea?

Release of erythropoietin into the bloodstream by peritubular cells in the renal cortex due to sensed hypoxia.

28

Where are erythrocytes produced?

Induced by erythropoietin, production occurs in the bone marrow.

29

What is hematocrit?

The percentage of the volume of whole blood that is composed of RBCs.

30

In patients with high risk of developing DIC and progressive hypofibrinogenemia, what should be carefully monitored?

Serum fibrinogen and platelet count.