Lipid Disorders — MCQs

10 questions

An adult male presented with a protruding abdomen, diarrhea, visual symptoms, and neurological manifestations. His LDL is low. Based on the peripheral smear finding shown in the image, what is the likely diagnosis?

A person is diagnosed with familial type IIa hyperlipoproteinemia. What is the basic defect in this type of hyperlipoproteinemia?

Which apolipoprotein is the primary structural component of LpA-I particles?

Which of the following enzymes is not targeted by hypolipidemic drugs?

What is the drug with the highest efficacy to increase plasma HDL?

Which of the following represents a desired lipid parameter for cardiovascular risk control in hypertension?

All of the following are true about nephrotic syndrome except?

HMG-CoA reductase is inhibited by:

Vitamin B12 deficiency can give rise to all of the following, except which of the following?

Q10

Which of these conditions is classified as a nephritic syndrome?

Lipid Disorders Indian Medical PG Practice Questions and MCQs

Question 1: An adult male presented with a protruding abdomen, diarrhea, visual symptoms, and neurological manifestations. His LDL is low. Based on the peripheral smear finding shown in the image, what is the likely diagnosis?

A. Abetalipoproteinemia (Correct Answer)
B. EDTA changes
C. Uremia
D. Burns
E. Liver disease

Explanation: ***Abetalipoproteinemia*** - The image shows **acanthocytes (spur cells)**, characterized by irregularly spaced, blunt projections, which are a hallmark of **abetalipoproteinemia** due to abnormal lipid metabolism and membrane defects. - The clinical presentation of a **protruding abdomen (steatorrhea/malabsorption)**, **diarrhea**, **visual symptoms (retinopathy)**, **neurological manifestations (ataxia, peripheral neuropathy)**, and **low LDL** all strongly point to abetalipoproteinemia, a disorder affecting the synthesis of B-apolipoprotein and chylomicrons. *EDTA changes* - **EDTA changes** typically manifest as **rouleaux formation**, platelet satellite formation, or cell shrinkage, with red blood cell morphology generally remaining normal in terms of spur cell formation. - These changes are **artifactual** and are not associated with the patient's systemic symptoms like malabsorption, neurological issues, or specific lipid profile findings. *Uremia* - While **uremia** can cause various red blood cell abnormalities, including **burr cells (echinocytes)** with regularly spaced, pointed projections, it generally does not cause the irregularly shaped **acanthocytes** seen in the image. - The systemic symptoms of uremia would primarily involve **renal dysfunction (e.g., elevated BUN, creatinine)**, which are not mentioned, and not specifically the **visual or malabsorption symptoms** seen here. *Burns* - Severe **burns** can lead to red blood cell fragmentation, causing **schistocytes** or **microspherocytes** due to heat-induced damage. - Burns are not typically associated with the formation of **acanthocytes** or the constellation of symptoms (malabsorption, neurological, visual) and lipid profile (low LDL) described in this patient. *Liver disease* - Advanced **liver disease (cirrhosis)** can cause **spur cell anemia** with acanthocytes due to altered cholesterol-to-phospholipid ratio in RBC membranes. - However, the key distinguishing feature is the **low LDL** in this patient, which is characteristic of abetalipoproteinemia, whereas liver disease typically does not present with specifically **low LDL** as a prominent feature. - Additionally, the constellation of **visual symptoms (retinopathy)** and **neurological manifestations** with malabsorption are more consistent with the fat-soluble vitamin deficiency (A, E, K) seen in abetalipoproteinemia rather than isolated liver pathology.

Question 2: A person is diagnosed with familial type IIa hyperlipoproteinemia. What is the basic defect in this type of hyperlipoproteinemia?

A. Lipoprotein lipase deficiency
B. Defective LDL receptor (Correct Answer)
C. Abnormal activity of Apo E
D. Overproduction of LDL

Explanation: ***Defective LDL receptor*** - **Familial hypercholesterolemia** (Type IIa hyperlipoproteinemia) is characterized by high levels of **LDL cholesterol** due to a genetic defect in the **LDL receptor** gene. - This defective receptor leads to impaired clearance of LDL particles from the bloodstream, resulting in their accumulation. *Lipoprotein lipase deficiency* - This defect is associated with **Type I hyperlipoproteinemia**, which is characterized by elevated **chylomicrons** and **triglycerides**, not primarily LDL cholesterol. - **Lipoprotein lipase (LPL)** is essential for the hydrolysis of triglycerides in chylomicrons and VLDL. *Abnormal activity of Apo E* - Variants of **Apolipoprotein E (Apo E)**, particularly Apo E2, are associated with **Type III hyperlipoproteinemia** (familial dysbetalipoproteinemia). - This condition involves increased levels of **chylomicron remnants** and **VLDL remnants** (IDL), not primarily isolated LDL elevation. *Overproduction of LDL* - While increased **LDL production** can contribute to elevated LDL levels, the primary genetic defect in familial type IIa hyperlipoproteinemia is strictly related to the impaired **clearance** of LDL due to a defective **LDL receptor**, rather than solely overproduction. - Many secondary causes of hypercholesterolemia can involve LDL overproduction, but Type IIa is specifically linked to the receptor defect.

Question 3: Which apolipoprotein is the primary structural component of LpA-I particles?

A. Apo B-48
B. Apo A-I (Correct Answer)
C. Apo A-II
D. Apo B-100

Explanation: ***Apo A-I*** - **Apolipoprotein A-I (Apo A-I)** is the main structural and functional protein of **high-density lipoprotein (HDL)**. - It plays a crucial role in **reverse cholesterol transport**, facilitating the removal of excess cholesterol from peripheral tissues back to the liver. *Apo B-48* - **Apo B-48** is found exclusively in **chylomicrons**, which are responsible for transporting dietary lipids from the intestines. - It is synthesized in the **intestine** and is critical for the assembly and secretion of chylomicrons. *Apo A-II* - **Apo A-II** is another apolipoprotein found in HDL particles, but it is not the primary structural component. - While present, it is less abundant than Apo A-I and its precise role is still being researched, though it may influence **HDL metabolism**. *Apo B-100* - **Apo B-100** is the primary structural protein of **low-density lipoprotein (LDL)** and very-low-density lipoprotein (VLDL). - It is essential for the binding of LDL to the **LDL receptor**, mediating the uptake of cholesterol into cells.

Question 4: Which of the following enzymes is not targeted by hypolipidemic drugs?

A. HMG Co A reductase
B. Lipoprotein lipase
C. Acyl CoA, cholesterol acyl transferase 1
D. Peripheral decarboxylase (Correct Answer)

Explanation: ***Peripheral decarboxylase*** - **Peripheral decarboxylase** (also known as DOPA decarboxylase) is involved in the synthesis of dopamine from L-DOPA and is a target for drugs used in **Parkinson's disease**, not hypolipidemic drugs. - Its inhibition by drugs like **carbidopa** or **benserazide** prevents the peripheral conversion of L-DOPA to dopamine, increasing L-DOPA availability for the brain. *HMG Co A reductase* - **HMG-CoA reductase** is the rate-limiting enzyme in cholesterol biosynthesis and is the primary target for **statins** (e.g., atorvastatin, simvastatin). - Statins effectively lower **LDL cholesterol** by inhibiting this enzyme, reducing endogenous cholesterol production. *Lipoprotein lipase* - **Lipoprotein lipase (LPL)** activity can be enhanced by certain hypolipidemic drugs, such as **fibrates**, which activate **PPAR-α**. - Increased LPL activity leads to enhanced hydrolysis of **triglycerides** from VLDL and chylomicrons, reducing triglyceride levels in plasma. *Acyl CoA, cholesterol acyl transferase 1* - **Acyl-CoA:cholesterol acyltransferase (ACAT) inhibitors** were developed as potential hypolipidemic agents to prevent cholesterol esterification and absorption. - While not widely used clinically due to efficacy and side effect profiles, **ACAT1** is involved in cholesterol esterification in the intestine and liver, making it a target for reducing cholesterol absorption.

Question 5: What is the drug with the highest efficacy to increase plasma HDL?

A. Ezetimibe (Zetia)
B. Gemfibrozil (Lopid)
C. Rosuvastatin (Crestor)
D. Nicotinic acid (Niacin) (Correct Answer)

Explanation: ***Nicotinic acid (Niacin)*** - Niacin has the **highest efficacy** among lipid-lowering drugs in increasing **plasma HDL cholesterol** levels, often by 15-35%. - It works by reducing the **hepatic synthesis of VLDL** (and thus LDL) as well as increasing the half-life of HDL. *Ezetimibe (Zetia)* - Ezetimibe primarily acts by inhibiting the **absorption of cholesterol** from the intestine. - While it lowers LDL cholesterol, its effect on **increasing HDL** is modest at best, typically in the single digits. *Gemfibrozil (Lopid)* - Gemfibrozil is a **fibrate** that is best known for significantly lowering **triglycerides** and increasing HDL cholesterol modestly. - Its effects on HDL are generally **less robust** than those of niacin, usually in the range of 10-20%. *Rosuvastatin (Crestor)* - Rosuvastatin is a **statin**, which primarily works by inhibiting **HMG-CoA reductase**, leading to a significant reduction in LDL cholesterol. - While statins can cause a small increase in HDL, typically about 5-10%, this effect is **not its primary mechanism** of benefit nor its greatest strength compared to niacin.

Question 6: Which of the following represents a desired lipid parameter for cardiovascular risk control in hypertension?

A. LDL / cholesterol > 10 mg%
B. HDL < 30 mg%
C. HDL / cholesterol ratio < 3.5
D. Cholesterol/HDL < 3.5 (Correct Answer)

Explanation: Cholesterol/HDL < 3.5 [1] - A total cholesterol-to-HDL ratio of less than 3.5 is considered optimal for cardiovascular risk reduction. - This ratio indicates a favorable balance, where the proportion of 'good' HDL cholesterol is relatively high compared to total cholesterol. LDL / cholesterol > 10 mg% - This option is unclear and likely misphrased, as LDL cholesterol is typically measured independently, not as a ratio to total cholesterol in this manner [1]. - Desired LDL levels are typically much lower than 100 mg/dL for high-risk individuals, and a ratio of LDL to total cholesterol greater than 0.1 (or 10%) is generally observed, but not a specific target for reduction [1]. HDL < 30 mg% - An HDL level less than 40 mg/dL (or 30 mg% for some contexts) is considered low and undesirable, as high HDL is protective against cardiovascular disease [1]. - This value would indicate increased cardiovascular risk, contrary to a desired parameter. HDL / cholesterol ratio < 3.5 - This ratio, as stated, is the inverse of the commonly used and desirable total cholesterol-to-HDL ratio. - If the HDL/cholesterol ratio were less than 3.5, it would imply a relatively low HDL compared to total cholesterol, which is an undesirable cardiovascular risk factor [1].

Question 7: All of the following are true about nephrotic syndrome except?

A. Hypoalbuminemia
B. Proteinuria >3.5 g/day
C. Increased risk of infection
D. Decreased serum triglycerides (Correct Answer)

Explanation: ***Decreased serum triglycerides*** - Nephrotic syndrome is characterized by **hyperlipidemia**, including **elevated total cholesterol** and **triglycerides**, due to increased hepatic synthesis of lipoproteins and decreased catabolism [1]. - This is a direct consequence of the body's attempt to compensate for low oncotic pressure and is a major diagnostic feature. *Hypoalbuminemia* - This is a **hallmark characteristic** of nephrotic syndrome, resulting from the significant loss of albumin in the urine [1]. - A low serum albumin level (typically <3.0 g/dL) contributes to **edema** due to decreased plasma oncotic pressure [1]. *Proteinuria >3.5 g/day* - This is the **defining diagnostic criterion** for nephrotic syndrome, indicating massive protein excretion through damaged glomerular capillaries [1]. - The protein loss is specifically defined as >3.5 grams per 1.73 m² of body surface area per day. *Increased risk of infection* - Patients with nephrotic syndrome are prone to infections, particularly **bacterial infections** like spontaneous bacterial peritonitis [1]. - This increased risk is due to the urinary loss of **immunoglobulins** (especially IgG), complement factors, and impaired cellular immunity [1].

Question 8: HMG-CoA reductase is inhibited by:

A. Lovastatin (Correct Answer)
B. Gemfibrozil
C. Nicotinic acid
D. Clofibrate

Explanation: ***Lovastatin*** - **Lovastatin** is part of the statin class of drugs, which are potent competitive inhibitors of **HMG-CoA reductase**. - By inhibiting this enzyme, statins reduce the synthesis of **mevalonate**, a precursor to **cholesterol**, thereby lowering LDL-cholesterol levels. *Gemfibrozil* - **Gemfibrozil** is a **fibrate**, a class of drugs that primarily act by activating **peroxisome proliferator-activated receptor alpha (PPAR-α)**. - Its main effect is to decrease **triglyceride** levels and increase **HDL cholesterol**, not directly inhibit HMG-CoA reductase. *Clofibrate* - **Clofibrate** is also a **fibrate** and operates similarly to gemfibrozil by activating **PPAR-α**. - It primarily reduces **triglycerides** and has a modest effect on increasing HDL, but does not inhibit HMG-CoA reductase. *Nicotinic acid* - **Nicotinic acid** (niacin or vitamin B3) reduces hepatic synthesis of **VLDL** and inhibits the release of **fatty acids** from adipose tissue. - This leads to a decrease in **LDL cholesterol** and triglycerides, and an increase in **HDL cholesterol**, but it does not directly inhibit HMG-CoA reductase.

Question 9: Vitamin B12 deficiency can give rise to all of the following, except which of the following?

A. Optic atrophy
B. Peripheral neuropathy
C. Myopathy (Correct Answer)
D. Myelopathy.

Explanation: ***Myopathy*** - **Myopathy**, or muscle disease, is not a direct consequence of **Vitamin B12 deficiency**. - **Vitamin B12 deficiency** primarily affects neurological and hematological systems due to its role in myelin synthesis and DNA production. [1] *Myelopathy* - **Myelopathy**, specifically subacute combined degeneration of the spinal cord, is a classic neurological complication of **Vitamin B12 deficiency**. - This involves demyelination of the posterior and lateral columns, leading to symptoms like **ataxia** and **sensory deficits**. *Optic atrophy* - **Optic atrophy** or **toxic amblyopia** can occur in severe cases of **Vitamin B12 deficiency**. - This damage to the **optic nerve** results in progressive vision loss. *Peripheral neuropathy* - **Peripheral neuropathy**, characterized by symptoms like **paresthesias**, numbness, and weakness, is a common neurological manifestation of **Vitamin B12 deficiency**. - It results from **demyelination** and axonal degeneration of peripheral nerves.

Question 10: Which of these conditions is classified as a nephritic syndrome?

A. Minimal Change Disease
B. Membranous Glomerulopathy
C. Post Infectious Glomerulonephritis (Correct Answer)
D. Focal Segmental Glomerulosclerosis

Explanation: ***Post infectious Glomerulonephritis*** - Characterized by **hematuria, hypertension, and edema**, typically following an infection, such as streptococcal pharyngitis [2]. - Immune-mediated response leads to **decreased GFR** and signs of nephritic syndrome [1][2]. *Focal segmental glomerulosclerosis* - Primarily causes **nephrotic syndrome**, characterized by proteinuria and edema rather than hematuria [2]. - Often associated with **secondary causes** like obesity or HIV, not typically post-infectious. *Membranous Glomerulopathy* - Results in significant **proteinuria** and is classified as a **nephrotic syndrome** rather than a nephritic one [2][3]. - It presents with **edema and hypoalbuminemia**, lacking the hallmark features of hematuria. *Minimal change disease* - Predominantly causes **nephrotic syndrome** with heavy proteinuria and little to no hematuria [2]. - Young children are commonly affected, and it responds well to **corticosteroid therapy** [1].

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