Hematology/Vasculitis Flashcards
Decreased activity of which enzyme causes sideroblastic anemia in patients taking isoniazid?
δ-aminolevulinate (ALA) synthase. Isoniazid inhibits the enzyme pyridoxine phosphokinase which normally converts pyridoxine (vitamin B6) to its active form, pyridoxal 5’ phosphate. Pyridoxal 5’ phosphate is a cofactor for δ-ALA synthase. Chloramphenicol and linezolid also can cause sideroblastic anemia. Sideroblastic anemia can also be caused by an X-linked deficiency in δ-ALA synthase, myelodysplastic syndrome, alcohol abuse and copper deficiency.
What is polyarteritis nodosa (PAN)?
PAN is segmental, transmural, necrotizing inflammation of medium to small sized arteries. Renal artery involvement is often prominent. It usually involves the vessels of the kidneys, heart, liver and GI tract. The pulmonary arteries are usually spared. There is a propensity of bead-like aneurysm formation formation, especially in the mesenteric circulation. Cutaneous manifestations occur in up to one-third of patients, and include palpable purpura.
What clotting factors does cryoprecipitate contain?
VIII, XIII, von Willebrand factor, and fibrinogen.
What is rat poison?
“Super wafarin”, a long-acting 4-hydroxycoumarin derivative that depletes vitamin K-dependent clotting factors.
What is a cavernous hemangioma?
Vascular malformations that often involve deeper tissues of the body, such as the liver and the brain. Gross examination shows a “mulberry-like” appearance due to their purple vascular clusters. On histology, they are composed of abnormal, dilated blood vessels with a thin adventitia lacking elastic fibers and smooth muscle. Because the walls lack these structural supports, they have a tendency to leak and hemorrhage.
Which leukemias are patients with Down Syndrome most at risk for?
10 to 20 fold increased risk for acute lymphoblastic leukemia (ALL), and also have an increased risk for acute myelogenous leukemia (especially acute megakaryoblastic leukemia).
Which two enzymes involved in heme biosynthesis are inhibited in lead poisoning?
δ-aminolevulinic acid (ALA) dehydratase and ferrochelatase. This causes sideroblastic anemia and basophilic stippling.
What are 6 notable causes of sideroblastic anemia?
Myelodysplastic syndromes Alcohol Lead poisoning Vitamin B6 deficiency Copper deficiency Isoniazid
Why are patients at risk for hypocalcemia following massive blood transfusions?
Prior to storage, whole blood is generally mixed with solutions containing citrate anticoagulant. Infused citrate can chelate serum calcium, causing hypocalcemia. This most often occurs after massive transfusions of more than 5 or 6 liters over 24hrs.
What is the inheritance pattern of C6PD deficiency?
X-linked recessive
What does the oxygen-dissociation curve for a solution of dissociated beta hemoglobin subunits look like (without alpha subunits)?
Shifted left (looks like a myoglobin dissociation curve).
What are characteristics of follicular lymphoma?
Second most common non-Hodgkin lymphoma. It is derived from follicular B cells and typically has a long, waxing and waning clinical course. Typically presents in middle-aged patients with painless lymph node enlargement or abdominal discomfort with an abdominal mass. Histology is notable for a mixture of cleaved and noncleaved follicle center cells in a nodular pattern. The majority of tumors have a t(14;18) translocation, resulting in overexpression of the bcl-2 oncogene that blocks programmed cell death.
Why are patients with sickle cell disease at increased risk for megaloblastic anemia?
Due to increased erythrocyte turnover (hemolytic anemia), patients have increased folic acid requirements which puts them at risk for relative folic acid deficiency and megaloblastic anemia.
Why do reticulocytes have a bluer appearance than mature RBCs on blood smear using a Wright-Giemsa stain?
They retain basophilic, reticular (mesh-like) network of residual rRNA.
What cancer are patients with chronic lymphedema (e.g. post axillary lymph node dissection for breast cancer) at risk for?
Angiosarcoma, also known as Stewart-Treves syndrome.