UWorld Flashcards
(38 cards)
Streptozyme test?
Detects antibodies against group A streptococcus and can be used to retrospectively diagnose streptococcal infections (eg, when evaluating for post-streptococcal glomerulonephritis {PSGN}). Patients with PSGN have edema and hypertension, no hemolytic anemia.
Hereditary angioedema?
A rare autosomal dominant disorder that is associated with painless episodes of swelling involving the face, lips, larynx, and extremities. It is caused by C1-inhibitor deficiency.
Production and function of erythropoietin (EPO)?
A glycoprotein hormone produced by peritubular fibroblast cells in the renal cortex. EPO is released into the bloodstream in response to renal tissue hypoxia and subsequently acts on erythrocyte progenitor cells (erythroid colony - forming unit cells) in the bone marrow to reduce apoptosis and increase differentiation into mature red blood cells.
Treatment of anemia in chronic kidney disease (CKD)?
These individuals are often treated with synthetic forms of EPO (eg, epoetin, darbepoetin) to supplement intrinsic EPO production and stimulate erythropoiesis. Because synthetic forms of EPO can rapidly deplete iron stores (due to increased red blood cell production), patients should be tested for iron deficiency prior to treatment with these agents.
Warm autoimmune hemolytic anemia is characterized by …?
Antibodies against antigens on the red cell membrane that result in phagocytosis in the reticuloendothelial system (eg, spleen).
Difference between coagulopathy and platelet defect?
Coagulopathies generally presents with deep-tissue bleeding into joints, muscles, and subcutaneous tissue. In contrast, platelet defects typically manifest with mucocutaneous bleeding (eg, epistaxis, petechiae).
Age-related changes in bone marrow?
The bone marrow of older patients has a higher quantity of fat and a reduced overall mass, which limits the functional reserve of hematopoietic cells. In addition, hematopoietic progenitor cell diversity and the response to stimulatory cytokines (eg, stem-cell factor, granulocyte macrophage colony-stimulating factor) are also impaired, thereby limiting the generation of new cells in response to stress. Because of these changes, older individuals cannot rapidly generate new blood cells.
The principal site of uric acid precipitation?
Uric acid (pKa = 5.4) is soluble at physiologic pH, bur precipitates in an acidic environment. The lowest pH along the nephron is found in the distal tubules and collecting ducts; so these are the segments of the nephron that become obstructed by uric acid crystals. Obstructive uropathy and acute renal failure follow.
Splenic congestion?
Occurs during a splenic sequestration crisis (marked hemoglobin decrease, rapidly enlarging spleen), which develops due to vaso-occlusion within the cords of Billroth and splenic pooling of erythrocytes.
Liver-associated macrocytosis?
Macrosistosis can occur in liver failure due to an increase in circulating phospholipids and cholesterol that adsorb onto erythrocytes, resulting in membrane expansion. However, liver-associated macrocytosis is generally mild (<110).
BCR-ABL1 fusion gene?
Characteristic abnormality seen in chronic myeloid leukemia. The BCR-ABL1 protein is a constituvely active tyrosine kinase, which results in uncontrolled proliferation of granulocytes.
Histopathological features of spleen in myelofibrosis?
The proliferation of erythroid, myeloid, and megakaryocytic progenitor cells in the spleen (large islands of hematopoietic progenitor cells) leads to a marked expansion of the splenic red pulp and usually results in dramatic splenomegaly.
Diffuse neutrophilic infiltration and follicular necrosis of spleen?
Acute infections of the spleen (eg, septic emboli from infective endocarditis) are typically associated with diffuse neutrophilic infiltration. Follicular necrosis is also common if the infection is due to group A Streptococcus.
Dilated sinusoids and fibrous nodules with hemosiderin of spleen.
Congestive splenomegaly due to portal hypertension (eg, from liver cirrhosis) is associated with dilated sinusoids, fibrosis of the red pulp, and hemosiderin-laden macrophages.
Complication in polycythemia vera?
Include peptic ulcer disease (altered mucosal blood flow due to increased viscosity) and gouty arthritis (higher erythrocyte turnover).
Erythropoietin functions?
EPO travels from the kidneys through the bloodstream to the bone marrow, where it binds to a surface receptor on erythrocyte colony-forming unit cells (ie, erythrocyte precursors). Binding activates the Janus kinase 2/signal transducer and activator of transcription (JAK/STAT) signaling pathway, which induces the transcription of proteins that inhibit erythrocyte precursor apoptosis and promote survival. Binding also activates signals that increase the differentiation of erythrocyte precursors into mature erythrocytes. Together, these effects accelerate the production of erythrocytes and increase curculating red blood cell counts.
Paradoxical PTT prolongation and false-positive RPR/VDRL results in antiphospholipid syndrome?
Antiphospholipid antibodies interfere with common serologic tests: lupus anticoagulant (LA) cross-reacts with phospholipid reagents in the activated PTT test, and anticardiolipin antibody (aCL) binds cardiolipin, the predominant antigen used in the rapid plasma reagin (RPR) and VDRL tests. Therefore, patients with circulating antiphospholipid antibodies have paradoxical PTT prolongation and false-positive RPR/VDRL results. Bleeding time and PT, which are coagulation tests unaffected by antiphospholipid antibodies, are normal.
Rhabdomyolysis?
Typically presents with muscle pain, red urine (ie, myoglobinuria), and elevated creatine kinase. Release of intracellular phosphate from muscel cells can precipitate calcium salts in damaged muscle and lead to hypocalcemia, but this is typically a delayed finding (24-72 hours after trauma).
Intrinsic platelet dysfunction in cirrhosis?
Cirrhosis is associated with intrinsic platelet dysfunction and thrombocytopenia due to decreased hepatic synthesis of thrombopoietin and increased splenic platelet sequestration (secondary to hypersplenism). Platelet dysfunction and significant thrombocytopenia (eg, platelets <50000/mm3) lead to mucocutaneous bleeding/petechiae and prolonged bleeding time.
DIC in exertional heat stroke?
Exertional heat stroke is a life-threatening multisystem disorder caused by inadequate body heat dissipation. Severe hyperthermia increases tissue oxygen demand and metabolic rate and shunts blood away from the central organs (eg, brain, kidneys, liver, GI tract) to the skin to dissipate heat. This can lead to tissue ischemia/necrosis and the release of procoagulant proteins (eg, tissue factor), which can trigger disseminated intravascular coagulation (DIC).
DIC due to gram-negative sepsis?
DIC is a common complication of sepsis (particularly with gram-negative organisms) because lipopolysaccharide is a procoagulant that triggers the coagulation cascade. This leads to the formation of fibrin- and platelet-rich thrombi in the vasculature, which consumes platelets (thrombocytopenia), coagulation factors (prolonged PT/PTT), and fibrinogen. Fibrinolysis is then triggered to degrade the clots, which elevates D-dimer (a fibrin degradation product) and depletes protein C, protein S, and antithrombin. The thrombi also often shear red blood cells, leading to microangiopathic hemolytic anemia (MAHA).
Factor XIII deficiency?
An extremely rare autosomal recessive disorder that causes clot instability. Affected patients often have delayed, recurrent bleeding after trauma or surgery. Hemophilia-like bleeding (eg, deep-tissue bleeding) is seen in factor XIII deficiency.
Difference between von Willebrand disease and Immune thrombocytopenia?
Patients with vWD experience easy bleeding from skin and mucosal sites, including the gingivae, nasal mucosa, gastrointestinal tract, and endometrium.
Immune thrombocytopenia produces isolated thrombocytopenia with episodic bleeding that is typically mucocutaneous (eg, petechiae, purpura, epistaxis).
Terminal deoxynucleotidyl transferase (TdT)?
Responsible for adding nucleotides to the V,D and J regions of the antibody gene for antibody diversity. It is a marker of immature lymphocytes, both B and T cells. Neoplastic cells in acute lymphoblastic leukemia (ALL) are TdT positive. ALL mainly affects children.
