Page 19 of 21
PA16.1-3 | Hemolytic Anemias — Graded Quiz
Graded
12 questions · Untimed · 2 attempts
Click any question card to reveal the correct answer.
A 19-year-old medical student donates blood at a camp. Two hours later she develops fever, chills, flank pain, and passes dark red-brown urine. Her Hb drops from 13.2 to 9.1 g/dL. Serum LDH is 1,840 U/L, unconjugated bilirubin 5.8 mg/dL, and haptoglobin is undetectable. Urine dipstick is positive for blood but microscopy shows no red cells. Which mechanism best explains the urine finding in this patient?
A
Haemoglobinuria due to free haemoglobin saturating renal tubular reabsorption after intravascular haemolysis
✓
B
Myoglobinuria from rhabdomyolysis triggered by the febrile reaction
C
Bilirubinuria from conjugated hyperbilirubinaemia caused by hepatocyte overload
D
Haematuria from renal cortical infarction secondary to vaso-occlusion
Click to reveal answer
A 25-year-old man with known hereditary spherocytosis (HS) is admitted with acute onset pallor, palpitations, and Hb of 4.8 g/dL (baseline 10.2 g/dL). Reticulocyte count is 0.4%. He had a febrile illness with rash one week prior. LDH is only mildly elevated. Which explanation best accounts for the dramatic drop in haemoglobin with a paradoxically low reticulocyte count?
A
Parvovirus B19 infection causing transient aplastic crisis by selectively infecting erythroid progenitors
✓
B
Hypersplenism causing sequestration of both red cells and reticulocytes in an enlarged spleen
C
Autoimmune haemolytic anaemia triggered by the viral infection converting extravascular to intravascular haemolysis
D
Iron deficiency from nutritional depletion during the febrile illness suppressing erythropoiesis
Click to reveal answer
A 14-year-old girl from Kerala presents with severe pallor, jaundice, and moderate splenomegaly. Hb is 6.2 g/dL, MCV 62 fL, MCH 19 pg. Peripheral smear shows microcytic hypochromic red cells, target cells, and nucleated RBCs. HbA2 is 5.8%. Her younger brother has similar findings; both parents are asymptomatic with MCV 68 fL and Hb 11.8 g/dL. Which conclusion about the parents is most accurate?
A
Both parents are β-thalassaemia trait carriers with elevated HbA2 and low MCV but no clinical anaemia
✓
B
One parent has sickle cell trait and the other has β-thalassaemia major, producing compound heterozygotes
C
Both parents have α-thalassaemia trait which produces the same phenotype as β-thalassaemia in homozygotes
D
Both parents are carriers of hereditary spherocytosis, an autosomal dominant disorder with incomplete penetrance
Click to reveal answer
A 32-year-old woman with β-thalassaemia major on regular transfusions presents with increasing abdominal discomfort and early satiety. She has received 180 units of packed red cells over 12 years. Her ferritin is 6,400 ng/mL. Liver biopsy confirms hepatic iron deposition. Her most life-threatening complication at this stage, and the reason it is life-threatening, is:
A
Cardiac siderosis causing restrictive and dilated cardiomyopathy leading to heart failure and arrhythmias
✓
B
Hepatic cirrhosis progressing to hepatocellular carcinoma from haemosiderotic hepatic damage
C
Secondary hypersplenism causing platelet trapping and severe haemorrhagic tendency
D
Pituitary iron deposition causing panhypopituitarism and secondary adrenal insufficiency
Click to reveal answer
A 40-year-old woman is investigated for episodic dark-coloured urine, especially in the morning, and recurrent episodes of abdominal pain. She has no jaundice. CBC shows Hb 8.2 g/dL, reticulocyte 6%, WBC 3.1 × 10⁹/L, platelets 88 × 10⁹/L. LDH is 1,120 U/L. Serum iron is elevated, TIBC is low, and ferritin is markedly raised. Flow cytometry of peripheral blood shows absence of CD55 and CD59 on red cells and granulocytes. Which single mechanism drives both the haemolysis and the thrombotic tendency in this condition?
A
Deficiency of GPI-anchored complement regulatory proteins allowing unrestricted complement-mediated lysis and platelet activation
✓
B
Somatic TP53 mutation in haematopoietic stem cells causing clonal cell proliferation and complement sensitivity
C
ADAMTS13 deficiency allowing ultra-large von Willebrand factor multimers to aggregate platelets and lyse red cells
D
Warm IgG autoantibodies targeting CD55 and CD59 directly, causing their removal and complement activation
Click to reveal answer
A 55-year-old woman with SLE presents with 4 weeks of progressive fatigue and pallor. Hb is 7.4 g/dL, reticulocyte count 11%, MCV 105 fL, indirect bilirubin 3.1 mg/dL. Peripheral smear shows spherocytes. The direct antiglobulin test (DAT) is positive for IgG but negative for C3d. The managing physician selects an immunosuppressive agent that reduces IgG autoantibody production. However, the patient's haemolysis does not remit. Which mechanism best explains the persistent haemolysis despite treatment?
A
IgG-coated spherocytes continue to be destroyed in the spleen by Fc-receptor-mediated phagocytosis as long as residual IgG remains bound to red cell surfaces
✓
B
C3d complement fragments bound to red cells independently activate the terminal complement pathway causing persistent intravascular haemolysis
C
The high MCV indicates folate deficiency causing dyserythropoiesis that perpetuates haemolysis despite autoantibody clearance
D
Spherocytes in SLE are derived from anti-phospholipid antibody damage to the red cell membrane and are not autoantibody-mediated
Click to reveal answer
A 6-year-old child presents with sudden onset pallor, dark urine, and jaundice following a meal of fava beans. CBC shows Hb 6.1 g/dL, reticulocytosis 18%. Peripheral smear demonstrates 'bite cells' and 'blister cells'. Heinz body preparation is positive. The attending paediatrician orders a direct antiglobulin test (DAT) which returns negative. Which statement correctly explains why the DAT is negative in this condition, and why Heinz bodies are present?
A
G6PD deficiency causes oxidative denaturation of haemoglobin into Heinz bodies without antibody involvement; haemolysis is complement-independent and intrinsic to the metabolic defect
✓
B
The DAT is negative because IgM antibodies (not IgG) mediate haemolysis and the standard Coombs reagent does not detect IgM bound to red cells
C
Heinz bodies form from precipitation of excess α-globin chains, and the DAT is negative because the defect is intracorpuscular membrane-based, not antibody-dependent
D
The false-negative DAT occurs because G6PD deficiency depletes complement on the red cell surface, removing C3d from the membrane before testing
Click to reveal answer
A 28-year-old man is investigated for fatigue. His CBC shows: Hb 11.8 g/dL, MCV 78 fL, reticulocyte 3.2%, unconjugated bilirubin 1.9 mg/dL (upper limit 1.2 mg/dL), LDH 380 U/L (upper limit 250 U/L), haptoglobin 0.3 g/L (lower limit 0.5 g/L). Direct Coombs test is negative. His spleen is palpable 2 cm below the costal margin. He has had two episodes of acute cholecystitis. Which diagnosis best explains this clinical and laboratory constellation?
A
Compensated hereditary spherocytosis with ongoing haemolysis below anaemia threshold, complicated by pigment gallstones
✓
B
Gilbert syndrome causing isolated unconjugated hyperbilirubinaemia with mildly elevated LDH from unrelated hepatic enzyme induction
C
Chronic liver disease with portal hypertension causing splenomegaly, mildly elevated LDH from hepatocyte necrosis, and jaundice
D
Iron deficiency anaemia with reactive thrombocytosis causing mildly elevated LDH and false-low haptoglobin
Click to reveal answer
A 36-year-old woman on methyldopa for essential hypertension develops anaemia (Hb 8.6 g/dL) after 4 months of therapy. Her reticulocyte count is 9%, peripheral smear shows spherocytes, and DAT is strongly positive for IgG. Methyldopa is discontinued. Which mechanism most accurately explains how methyldopa causes autoimmune haemolytic anaemia?
A
Methyldopa alters T-regulatory cell function, inducing a true autoimmune response with autoantibodies targeting native Rh antigens on all red cells, not just drug-coated cells
✓
B
Methyldopa binds irreversibly to red cell membrane proteins as a hapten, and IgG antibodies against the drug-red cell complex cause haemolysis only while the drug is present
C
Methyldopa activates complement via the lectin pathway on red cell surfaces, causing C3d deposition and complement-mediated intravascular haemolysis
D
Methyldopa is an immune complex former; drug-antibody complexes deposit non-specifically on red cells, activating complement and causing innocent bystander haemolysis
Click to reveal answer
In a rural hospital, four patients present with acute haemolytic anaemia. The following data is collected. Which patient's presentation is MOST consistent with cold autoimmune haemolytic anaemia (cold agglutinin disease)?
A
Patient B: 58-year-old, haemolysis worsening in winter, acrocyanosis on cold exposure, DAT positive for C3d only, IgM antibody detected, smear shows red cell agglutinates
✓
B
Patient A: 32-year-old woman with SLE, spherocytes on smear, DAT positive for IgG, haemolysis worsening at 37°C
C
Patient C: 19-year-old man, haemolysis after primaquine, bite cells on smear, DAT negative, Heinz bodies positive
D
Patient D: 45-year-old man, haemolysis following blood transfusion, haemoglobinuria, DAT positive for IgG, no agglutinates on smear
Click to reveal answer
A 22-year-old woman is found to have Hb 10.9 g/dL, MCV 65 fL, serum ferritin 86 ng/mL (normal), serum iron 14 µmol/L (normal), and TIBC 62 µmol/L (normal). Her HbA2 is 4.2% and HbF is 2.8%. She is planning pregnancy. Her partner's CBC is normal (MCV 85 fL, Hb 14.3 g/dL). What is the single most important implication for her prenatal counselling?
A
Her partner's normal MCV makes β-thalassaemia major in offspring unlikely, but the partner should have HPLC to definitively exclude carrier status before reassurance
✓
B
Her HbF of 2.8% confirms β-thalassaemia major and she requires immediate transfusion before pregnancy can proceed
C
Since ferritin is normal, iron supplementation alone will correct her anaemia and MCV before conception
D
Both parents must be carriers given her phenotype; prenatal diagnosis should be offered regardless of partner testing
Click to reveal answer
A 48-year-old woman with chronic kidney disease (CKD stage 4) presents with Hb 7.8 g/dL, MCV 84 fL, reticulocyte 1.2%, serum erythropoietin 9 mU/mL (expected >40 at this Hb level). She is transfusion-dependent every 6 weeks. At her last clinic visit, 2 weeks post-transfusion, her Hb was 9.6 g/dL but LDH is now 890 U/L (reference <250), unconjugated bilirubin 3.8 mg/dL, haptoglobin undetectable, and new schistocytes appear on her smear. Her BP is 180/110 mmHg and creatinine rose sharply to 6.4 mg/dL (baseline 3.1 mg/dL). Which is the most likely new diagnosis explaining the acute decompensation?
A
Thrombotic thrombocytopenic purpura (TTP) causing ADAMTS13-deficient microangiopathic haemolytic anaemia superimposed on CKD
B
Haemolytic uraemic syndrome (HUS) from Shiga toxin or complement dysregulation causing MAHA with acute worsening of renal function
✓
C
Acute haemolytic transfusion reaction from alloimmunisation causing delayed intravascular haemolysis 2 weeks post-transfusion
D
Iron overload from transfusion dependency causing haemolytic anaemia and acute tubular necrosis worsening creatinine
Click to reveal answer