Comprehensive Basic Science Flashcards
7 cards from real NBME practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Comprehensive Basic Science flashcards as text
A child with recurrent bacterial infections is found to have absent germinal centers on lymph node biopsy and very low serum immunoglobulins. Which condition is most likely?
Answer: X-linked agammaglobulinemia (Bruton disease)
Bruton disease results from a BTK kinase mutation causing B cell maturation arrest, absent plasma cells/germinal centers, and profound hypogammaglobulinemia.
A mother is blood type O and her newborn has blood type A. Hemolytic disease of the newborn is suspected. Which antibody class crosses the placenta?
Answer: IgG
IgG is the only antibody isotype that crosses the placenta via neonatal Fc receptor (FcRn)-mediated transcytosis, mediating hemolytic disease of the newborn.
A patient with myasthenia gravis has antibodies against acetylcholine receptors. This represents which type of hypersensitivity reaction?
Answer: Type II (cytotoxic/antibody-mediated)
Type II hypersensitivity involves IgG/IgM antibodies targeting cell-surface or matrix antigens, blocking receptor function as in myasthenia gravis.
A patient is found to carry a balanced reciprocal translocation between chromosomes 9 and 22, producing the BCR-ABL fusion gene. Which malignancy is this most associated with?
Answer: Chronic myelogenous leukemia
The Philadelphia chromosome t(9;22) creates BCR-ABL, a constitutively active tyrosine kinase that drives CML proliferation and is targeted by imatinib.
A 30-year-old woman has a lesion in the right optic tract. Which visual field defect results?
Answer: Left homonymous hemianopia
The right optic tract carries fibers from the nasal retina of the left eye and temporal retina of the right eye, so its lesion causes loss of the left visual field in both eyes.
During embryogenesis, failure of neural crest cell migration to the foregut leads to which condition?
Answer: Hirschsprung disease
Neural crest cells populate the myenteric plexus; failure of caudal migration causes aganglionic megacolon (Hirschsprung disease) with functional obstruction.
A 45-year-old presents with muscle weakness, hyporeflexia, and autonomic dysfunction that improves with repetitive stimulation on EMG. Which condition is most likely?
Answer: Lambert-Eaton myasthenic syndrome
Lambert-Eaton syndrome involves antibodies against presynaptic VGCC, causing reduced ACh release that paradoxically improves with repetitive stimulation as calcium accumulates.