G6PD Deficiency and Warm Autoimmune Hemolytic Anemia are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
G6PD Deficiency vs Warm Autoimmune Hemolytic Anemia at a glance
G6PD Deficiency: X-linked enzyme deficiency causing episodic oxidative hemolysis in response to drugs, infection, or fava beans.
Warm Autoimmune Hemolytic Anemia: IgG-mediated extravascular hemolysis with positive direct Coombs (DAT) — first-line treatment is steroids.
Try two board-style questions on G6PD Deficiency vs Warm Autoimmune Hemolytic Anemia
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Question 1HematologyMedium
A 26-year-old African American man presents 3 days after starting trimethoprim-sulfamethoxazole for a UTI with acute jaundice, dark urine, and fatigue. CBC shows Hgb 8.4 g/dL with reticulocytosis. Peripheral smear shows bite cells and Heinz bodies. Direct Coombs test is negative. Which is the most likely diagnosis?
ASickle cell disease
BHereditary spherocytosis
CPyruvate kinase deficiency
DG6PD deficiency
Reveal answer & full explanation
Correct answer: D — G6PD deficiency
ASickle cell disease
BHereditary spherocytosis
CPyruvate kinase deficiency
DG6PD deficiency✓
Why G6PD deficiency is correct
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked recessive enzyme defect causing oxidative hemolysis
Triggered by drugs including trimethoprim-sulfamethoxazole (TMP-SMX), dapsone, primaquine, and nitrofurantoin, as well as infections or fava beans
Bite cells (from splenic phagocytosis of Heinz bodies) and Heinz bodies (denatured Hgb precipitates) are classic findings on peripheral smear
A negative direct Coombs test distinguishes G6PD deficiency from autoimmune hemolytic anemia
Why the others are wrong
Sickle cell disease — shows sickle cells on peripheral smear; not triggered acutely by sulfonamide drugs in this manner
Hereditary spherocytosis — shows spherocytes with increased osmotic fragility; not drug-triggered oxidative hemolysis
Pyruvate kinase deficiency — an autosomal recessive, Coombs-negative congenital hemolytic anemia that causes chronic lifelong hemolysis with echinocytes (burr cells) on smear; it is not precipitated by oxidant drugs such as TMP-SMX and does not produce bite cells or Heinz bodies
Question 2HematologyMedium
A 34-year-old woman presents with 3 weeks of progressive fatigue, exertional dyspnea, and scleral icterus. Examination shows pallor and mild splenomegaly. Labs reveal hemoglobin 8.1 g/dL, elevated reticulocyte count, elevated LDH, indirect hyperbilirubinemia, and low haptoglobin. The peripheral smear shows spherocytes, and the direct antiglobulin test is positive for IgG. Among coexisting conditions, which of the following is the strongest risk factor for developing this disorder?
AAutoimmune type 1 diabetes mellitus
BSystemic lupus erythematosus (SLE)
CSeropositive rheumatoid arthritis
DHashimoto autoimmune thyroiditis
Reveal answer & full explanation
Correct answer: B — Systemic lupus erythematosus (SLE)
AAutoimmune type 1 diabetes mellitus
BSystemic lupus erythematosus (SLE)✓
CSeropositive rheumatoid arthritis
DHashimoto autoimmune thyroiditis
Why Systemic lupus erythematosus (SLE) is correct
The vignette describes warm autoimmune hemolytic anemia (warm AIHA): IgG-mediated extravascular hemolysis with spherocytes and a DAT positive for IgG.
Among autoimmune diseases, SLE is the single most commonly associated condition and the strongest risk factor for secondary warm AIHA. New warm AIHA should prompt evaluation for SLE (ANA, anti-dsDNA).
SLE-associated cytopenias are common, and AIHA can be a presenting or defining hematologic feature of lupus.
Why the others are wrong
Seropositive rheumatoid arthritis is a recognized autoimmune association with warm AIHA, but it is far weaker and less common than SLE; it functions as a relative-risk-weighting distractor.
Hashimoto autoimmune thyroiditis is a common autoimmune thyroid disease, but it is not a meaningful driver of secondary warm AIHA and is not part of the standard secondary-cause workup.
Autoimmune type 1 diabetes mellitus is autoimmune in origin, but it is not an established risk factor for warm AIHA; it serves as a near-miss autoimmune lure.
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X-linked enzyme deficiency causing episodic oxidative hemolysis in response to drugs, infection, or fava beans.
IgG-mediated extravascular hemolysis with positive direct Coombs (DAT) — first-line treatment is steroids.
Classic presentation
Dark urine and jaundice 1-3 days after starting TMP-SMX (or dapsone, or fava bean ingestion) in a young man of African or Mediterranean descent.; Acute hemolytic episode 24-72 hours after oxidant exposure: dark/cola-colored urine (hemoglobinuria), back/abdominal pain, jaundice, fatigue, dyspnea; Neonatal jaundice — especially…
Anemia with spherocytes on smear and a positive direct Coombs (DAT) for IgG ± C3.; Insidious or acute fatigue, dyspnea on exertion, pallor; Jaundice, dark urine in severe cases; Constitutional symptoms if underlying lymphoma or autoimmune disease; Fever, abdominal pain in fulminant hemolysis; Pallor with scleral icterus; Splenomegaly…
Workup / key labs
Low quantitative G6PD enzyme activity in a stable patient (away from acute hemolytic episode). Not part of routine US newborn screening in most states; measure G6PD activity in a jaundiced newborn with suspected hemolysis or bilirubin rising despite intensive phototherapy (AAP 2022).; CBC — normocytic anemia, reticulocytosis (peaks ~7…
Evidence of hemolysis (elevated reticulocytes, LDH, indirect bilirubin; low haptoglobin) + positive direct Coombs (DAT) for IgG ± C3; spherocytes on smear are supportive (usually present) but not required.; CBC — normocytic or macrocytic anemia (macrocytic due to reticulocytosis); often other cytopenias if Evans syndrome; Peripheral…
Imaging
Not routinely indicated
CT chest/abdomen/pelvis if lymphoma or solid tumor suspected
First-line treatment
Acute hemolysis: identify and remove offending agent immediately; Supportive care — IV fluids to maintain renal perfusion and clear hemoglobinuria; Transfusion for severe symptomatic anemia or hemodynamic instability; Prevention is primary: educate patient about drugs and foods to avoid; provide list of contraindicated medications;…
Prednisone 1 mg/kg/day (typically 60-100 mg) — first-line; ~70-80% initial response; taper slowly over 3-6 months once Hb stabilizes; Folic acid 1-5 mg/day (chronic hemolysis depletes folate); Identify and treat underlying cause: discontinue offending drug, treat lymphoma/CLL, manage autoimmune disease; Transfuse for severe or…
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Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.