MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 58
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
A child has hemolytic anemia with schistocytes, thrombocytopenia and acute kidney injury without diarrhea. ADAMTS13 activity is 60%. Which pathway is most likely abnormal?
Atypical (complement-mediated) HUS is caused by uncontrolled alternative complement activation, e.g., factor H mutations or antibodies. Normal ADAMTS13 excludes TTP; no diarrhea argues against STEC-HUS.
A newborn has severe thrombocytopenia with absent megakaryocytes in the marrow, normal limbs, and very high thrombopoietin. Which gene is most likely mutated?
Congenital amegakaryocytic thrombocytopenia is caused by MPL (thrombopoietin receptor) mutations and often progresses to marrow failure. ITGA2B mutations cause Glanzmann thrombasthenia.
In pernicious anemia, destruction of gastric parietal cells typically causes which additional laboratory finding?
Autoimmune gastritis causes achlorhydria; without acid feedback, G cells release more gastrin, so serum gastrin is high. Methylmalonic acid is raised, not low, in B12 deficiency.
A healthy 3-year-old has Hb 6.0 g/dL (60 g/L), reticulocytes 0.1%, normal MCV and normal WBC and platelets after a viral illness. HbF and red cell adenosine deaminase are normal. The most likely diagnosis is:
Transient erythroblastopenia occurs at 1–4 years, is normocytic, has normal HbF and eADA, and recovers in weeks. Diamond-Blackfan anemia presents in infancy with macrocytosis and raised HbF and eADA.
Two years after gastric bypass surgery, a patient has anemia and neutropenia. The marrow shows vacuoles in erythroid and myeloid precursors and some ring sideroblasts. B12 and folate are normal. The most likely cause is:
Copper deficiency, common after bariatric surgery or with zinc excess, causes anemia, neutropenia, precursor vacuoles and ring sideroblasts, mimicking myelodysplasia. It reverses with copper replacement. Iron deficiency does not cause neutropenia with vacuolated precursors.
A 60-year-old has isolated severe normocytic anemia, reticulocytes near 0%, and a marrow with almost no erythroid precursors but normal myeloid and megakaryocytic cells. CT shows an anterior mediastinal mass. The likely diagnosis is:
Pure red cell aplasia affects only the erythroid line and is classically associated with thymoma. Aplastic anemia reduces all three cell lines.
A child has severe hemolysis, MCV about 55 fL and bizarre micropoikilocytes and fragments. The red cells fragment when heated to about 45 °C, compared with about 49 °C for normal cells. The diagnosis is:
Hereditary pyropoikilosis is a severe spectrin disorder related to hereditary elliptocytosis; its cells are unusually heat-sensitive and fragment at a lower temperature. Burns damage normal cells only when the patient is heated, with no inherited heat sensitivity.
A family has mild hemolysis with many stomatocytes, MCV 110 fL, MCHC 29 g/dL (290 g/L) and increased osmotic fragility. B12 and folate are normal. The most likely diagnosis is:
In overhydrated stomatocytosis, cells gain sodium and water, so they are large with low MCHC and lyse easily in hypotonic saline. Xerocytosis is the dehydrated form, with high MCHC and decreased osmotic fragility.
By WHO criteria, a ring sideroblast is an erythroblast with at least 5 iron granules encircling at least:
WHO defines a ring sideroblast as an erythroblast with 5 or more Prussian blue–positive granules covering at least one-third of the nuclear circumference. These iron-loaded mitochondria are typical of sideroblastic anemias and some MDS.
A traveler from the Andes of Peru has fever and severe hemolytic anemia. The smear shows small red-violet rods and coccobacilli on the surface of many red cells. The most likely organism is:
Bartonella bacilliformis causes Oroya fever in Andean valleys and attaches to red cells as small rods, causing hemolysis. Anaplasma forms morulae in neutrophils, and Babesia forms intracellular rings.
In Philadelphia-positive B-lymphoblastic leukemia of childhood, the BCR::ABL1 fusion most often produces a protein of about:
Most Ph-positive ALL (especially in children) has a break in the minor bcr region, giving the p190 (e1a2) protein. p210 is typical of CML; p230 is linked to a neutrophilic CML-like picture.
A newborn with Down syndrome has circulating blasts that disappear without treatment within 3 months. Which gene is typically mutated in these blasts?
Transient abnormal myelopoiesis in Down syndrome is caused by GATA1 mutations in megakaryoblasts and usually resolves spontaneously, though some infants later develop myeloid leukemia.
An elderly man has skin nodules and pancytopenia. Blasts are CD4+, CD56+, CD123 bright, TCL1+ and negative for MPO and CD3. The diagnosis is:
Co-expression of CD4, CD56, bright CD123 and TCL1 without lineage markers is typical of BPDCN, which often starts in the skin. Monocytic AML expresses CD14/CD64 and lysozyme.
A neutrophil containing a large, homogeneous, pale purple mass that pushes its nucleus aside is seen in a smear from synovial fluid. This is:
The LE cell is a neutrophil that has engulfed denatured, homogeneous nuclear material, linked to lupus. A tart cell is usually a monocyte that has ingested a whole nucleus that still shows chromatin pattern.
A 9-year-old girl has raised transaminases, hypergammaglobulinaemia and negative ANA and ASMA. Which antibody would best support type 2 autoimmune hepatitis?
Type 2 autoimmune hepatitis mainly affects children and is defined by anti-LKM-1 (targeting CYP2D6), usually without ANA or ASMA. Anti-SLA is seen mainly in type 1 disease.
A patient with chronic hepatitis C has purpura, arthralgia and low C4. A serum kept at 37 °C then chilled forms a precipitate containing polyclonal IgG and monoclonal IgM with rheumatoid factor activity. This is:
Type II mixed cryoglobulins contain monoclonal IgM with RF activity bound to polyclonal IgG and are strongly linked to hepatitis C. Type I contains only a monoclonal immunoglobulin, often in myeloma or Waldenström disease.
In the MHC class II pathway, the invariant chain (Ii) mainly serves to:
The invariant chain occupies the class II groove in the ER; in the endosome it is degraded to CLIP, which HLA-DM exchanges for exogenous peptide. Transport of cytosolic peptides into the ER is done by TAP.
Before starting abacavir for HIV, the laboratory is asked to test for which allele to prevent a serious hypersensitivity reaction?
HLA-B*57:01 carriers have a high risk of abacavir hypersensitivity, so screening is recommended before treatment. HLA-B27 relates to spondyloarthritis, not drug reactions.
Dendritic cells can present peptides from ingested (exogenous) antigens on MHC class I to activate CD8 T cells. This process is called:
Cross-presentation lets dendritic cells prime CD8 T cells against viruses or tumours that do not infect the dendritic cell itself. Normally exogenous antigen goes to MHC class II.
Inherited variations in immunoglobulin constant regions between individuals of the same species, such as Gm markers on IgG, are called:
Allotypes are allelic differences within a species (e.g., Gm on γ chains, Km on κ chains). Isotypes are the class and subclass differences shared by all normal members of a species.