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Blood & Lymphoreticular/Immune Systems — Step 1 practice questions
70 questions in this area, with an explanation for every answer choice.
Three samples below, free and without an account.
How this shows up on Step 1
Anaemia questions are approached through indices before anything else, and the classification tree does most of the work. Immunology is examined as mechanism: which cell, which cytokine, which step failed. Immunodeficiencies and hypersensitivity reactions recur often enough that they are worth knowing cold.
Sample questions
Sample question 1
An infant has delayed separation of the umbilical cord, recurrent infections without pus formation, and marked leukocytosis. Which of the following is the most likely diagnosis?
Explanations
A. DiGeorge syndrome
DiGeorge syndrome presents with hypocalcemia and cardiac defects, a different presentation.
B. Bruton agammaglobulinemia
Bruton agammaglobulinemia presents with recurrent bacterial infections from absent B cells, without this specific cord separation/pus pattern.
C. Leukocyte adhesion deficiency · correct
Delayed umbilical cord separation, recurrent infections WITHOUT pus formation (since neutrophils cannot properly migrate to sites of infection), and marked leukocytosis (since neutrophils accumulate in blood but cannot exit vessels) are classic for leukocyte adhesion deficiency, caused by defective integrin (CD18) function.
D. Chronic granulomatous disease
CGD presents with catalase-positive organism infections and granuloma formation, not this delayed cord separation/absent pus pattern.
E. Chediak-Higashi syndrome
Chediak-Higashi syndrome presents with partial albinism and giant granules in neutrophils, a different presentation.
Sample question 2
A patient who underwent splenectomy after a traumatic injury is at increased long-term risk for infection with which of the following types of organisms?
Explanations
A. Anaerobic bacteria exclusively
While anaerobic infections can occur in many contexts, the classic, specific risk after splenectomy relates to encapsulated organisms.
B. Only organisms transmitted via respiratory droplets
This does not accurately describe the specific organism risk category relevant to asplenia.
C. Encapsulated bacteria (e.g., S. pneumoniae, H. influenzae, N. meningitidis) · correct
The spleen plays a critical role in opsonization-dependent clearance of encapsulated bacteria; asplenic patients are at significantly increased risk for overwhelming infections with S. pneumoniae, H. influenzae, and N. meningitidis, warranting specific vaccination.
D. Viruses exclusively, with no bacterial risk
The primary concern is specifically with encapsulated BACTERIA, not exclusively viruses.
E. Intracellular fungi exclusively
This is not the primary or classic post-splenectomy infection risk category.
Sample question 3
A 4-year-old child has fever, bone pain, pallor, bruising, and lymphadenopathy. Complete blood count shows anemia, thrombocytopenia, and 60% blasts that stain positive for terminal deoxynucleotidyl transferase and CD10. Which of the following sites requires specific prophylactic treatment in this disease?
Explanations
A. The central nervous system, via intrathecal chemotherapy · correct
Acute lymphoblastic leukemia — the most common childhood malignancy, peaking at ages 2–5 — shows TdT-positive lymphoblasts (CD10 and CD19 in B-ALL). Because systemic chemotherapy penetrates the blood-brain barrier poorly, the CNS is a sanctuary site where blasts survive and cause relapse, so intrathecal chemotherapy prophylaxis is standard (the testes are the other sanctuary). Prognosis is excellent in standard-risk children; t(12;21) is favorable and t(9;22) unfavorable.
B. The liver, via hepatic artery infusion
Hepatic infusion is used for hepatic metastases of solid tumors.
C. The lungs, via inhaled chemotherapy
The lungs are not a sanctuary site.
D. The skin, via topical chemotherapy
Skin-directed therapy applies to cutaneous T-cell lymphoma.
E. The kidneys, via renal irradiation
Renal irradiation is not indicated.
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