A patient with severely elevated serum triglycerides (>1000 mg/dL) is at immediate risk of:
AOnly hypercholesterolemia
BAcute pancreatitis
CPeripheral neuropathy
DMyocardial infarction only
Correct Answer:
B. Acute pancreatitis
EXPLANATION
Severe hypertriglyceridemia (>1000 mg/dL) significantly increases the risk of acute pancreatitis due to pancreatic inflammation caused by triglyceride-rich lipoproteins.
In the condition of hypertriglyceridemia with normal LDL levels, which genetic defect is most likely?
ALDL receptor deficiency
BLipoprotein lipase or apoC-II deficiency
CCETP deficiency
DApoB gene mutation
Correct Answer:
B. Lipoprotein lipase or apoC-II deficiency
EXPLANATION
Deficiency of lipoprotein lipase or its cofactor apoC-II results in severe hypertriglyceridemia with elevated chylomicrons and VLDL but relatively normal LDL levels.
Tangier disease is associated with deficiency of which protein?
AApoA-I
BABCA1 transporter
CLipoprotein lipase
DApoB-100
Correct Answer:
B. ABCA1 transporter
EXPLANATION
Tangier disease results from mutations in the ABCA1 gene, which encodes a cholesterol transporter. This leads to severe HDL deficiency and accumulation of cholesterol esters in tissues.
A patient presents with neurodegenerative symptoms, progressive neuropathy, and xanthomas. Plasma cholestanol and cholestane-3-beta,5-alpha,6-beta-triol levels are markedly elevated. Which genetic defect is most likely?
Correct Answer:
B. CYP27A1 mutation (sterol 27-hydroxylase deficiency)
EXPLANATION
CYP27A1 mutations cause cerebrotendinous xanthomatosis (CTX), characterized by elevated cholestanol and cholestane triol precursors due to impaired side-chain oxidation of cholesterol. This leads to progressive neurological deterioration, cataracts, and diarrhea. Chenodeoxycholic acid therapy is beneficial.
A 35-year-old patient with atherosclerosis has normal LDL cholesterol but elevated lipoprotein(a). Which genetic polymorphism is primarily responsible for high Lp(a) levels?
AAPOE gene variations
BLPA gene variations affecting apo(a) size
CLDLR gene mutations
DPCSK9 gene polymorphisms
Correct Answer:
B. LPA gene variations affecting apo(a) size
EXPLANATION
Lipoprotein(a) levels are predominantly determined by genetic variations in the LPA gene, which encodes apolipoprotein(a). Smaller isoforms are associated with higher plasma Lp(a) levels and increased cardiovascular risk, independent of LDL cholesterol levels.
A deficiency of apolipoprotein B-48 synthesis would primarily affect which lipid transport pathway?
ACholesterol esterification
BChylomicron formation and dietary lipid absorption
CHDL-mediated reverse cholesterol transport
DLDL receptor-mediated endocytosis
Correct Answer:
B. Chylomicron formation and dietary lipid absorption
EXPLANATION
ApoB-48 is the truncated form of apoB synthesized in intestinal enterocytes and is essential for chylomicron assembly and secretion. Its deficiency causes abetalipoproteinemia, characterized by fat malabsorption and severe deficiency of fat-soluble vitamins.
During the fed state, acetyl-CoA carboxylase (ACC) is activated by which mechanism?
AAllosteric activation by AMP
BPhosphorylation by AMPK
CPhosphorylation by insulin-activated PKA
DAllosteric activation by citrate and phosphorylation by PKB/Akt
Correct Answer:
D. Allosteric activation by citrate and phosphorylation by PKB/Akt
EXPLANATION
In the fed state, high citrate levels allosterically activate ACC, and insulin signaling causes PKB/Akt to phosphorylate and activate ACC. This promotes fatty acid synthesis. Conversely, AMPK phosphorylation inactivates ACC during energy deprivation.
A patient with primary biliary cholangitis shows elevated cholestanol levels. Which enzyme defect is most likely responsible?
ASterol 7-alpha-hydroxylase
BSterol 27-hydroxylase
CHMG-CoA reductase
DACAT
Correct Answer:
B. Sterol 27-hydroxylase
EXPLANATION
Sterol 27-hydroxylase catalyzes the side-chain oxidation of cholesterol to form bile acid precursors. Its deficiency or dysfunction leads to cholestanol accumulation and neuropathy. Elevated cholestanol is a characteristic finding in sterol 27-hydroxylase deficiency.
In Type III hyperlipoproteinemia (Familial Dysbetalipoproteinemia), the primary defect involves:
AApolipoprotein E2 isoform with impaired receptor binding
BLDL receptor deficiency
CLipoprotein lipase deficiency
DABCA1 transporter mutation
Correct Answer:
A. Apolipoprotein E2 isoform with impaired receptor binding
EXPLANATION
Type III hyperlipoproteinemia results from apoE2 homozygosity combined with another genetic or environmental factor. ApoE2 has reduced affinity for lipoprotein receptors, impairing remnant particle clearance.
The oxidative stress marker oxidized LDL (oxLDL) primarily activates which receptor to promote foam cell formation?
ALDL receptor
BSR-A (Scavenger receptor A) and LOX-1 (Lectin-like oxidized LDL receptor-1)
CHDL receptor
DApoE receptor
Correct Answer:
B. SR-A (Scavenger receptor A) and LOX-1 (Lectin-like oxidized LDL receptor-1)
EXPLANATION
OxLDL is recognized by scavenger receptors (SR-A and LOX-1) on macrophages, not by the classical LDL receptor. This leads to unregulated cholesterol uptake and foam cell formation in atherosclerosis.
