Biochemistry
5 questionsA patient's relatives sent a message on social media to the consulting doctor, mentioning that the patient's urinary coproporphyrin test is positive. What is the probable cause?
A neonate was brought to the hospital with chief complaints of poor feeding, vomiting, acidosis, and cataract. Benedict's test on urine was positive, but urinary glucose was negative. What is the defective enzyme in the above-mentioned disorder?
A patient presents with a skin rash that is exaggerated on sun exposure. What is the repair mechanism involved in this condition?
A 45-year-old patient presents with joint pain and weakness and is known to have homocystinuria. Which vitamin is required in the treatment?
A patient came to the hospital with severe abdominal pain, and lipase levels were elevated. On imaging, a stone is found in the common bile duct (CBD). Which enzyme is most likely elevated in this condition?
NEET-PG 2024 - Biochemistry NEET-PG Practice Questions and MCQs
Question 151: A patient's relatives sent a message on social media to the consulting doctor, mentioning that the patient's urinary coproporphyrin test is positive. What is the probable cause?
- A. Lead poisoning (Correct Answer)
- B. Asbestosis
- C. Silicosis
- D. Mercury poisoning
- E. Arsenic poisoning
Explanation: ***Lead poisoning*** - **Lead poisoning** is associated with an increase in **urinary coproporphyrin III**, as lead inhibits the enzyme **coproporphyrinogen oxidase** in the heme synthesis pathway. - This leads to the accumulation and excretion of **coproporphyrin III** in the urine, making it a valuable biomarker for lead exposure. *Asbestosis* - **Asbestosis** is a chronic lung disease caused by inhaling **asbestos fibers**, leading to diffuse interstitial fibrosis. - It does not directly affect the **heme synthesis pathway** or cause an increase in urinary coproporphyrins. *Silicosis* - **Silicosis** is a chronic occupational lung disease caused by inhaling **crystalline silica dust**, resulting in pulmonary fibrosis. - It is not associated with alterations in **porphyrin metabolism** or increased urinary coproporphyrin levels. *Mercury poisoning* - While **mercury poisoning** can affect various organ systems, including renal and neurological, it is not primarily associated with disturbances in the **heme synthesis pathway** or elevated urinary coproporphyrins. - **Mercury poisoning** often manifests with symptoms like **tremors**, **neurological deficits**, and **kidney damage**. *Arsenic poisoning* - **Arsenic poisoning** causes a variety of systemic effects including gastrointestinal symptoms, peripheral neuropathy, and skin changes (hyperpigmentation, hyperkeratosis). - Unlike lead poisoning, **arsenic does not significantly elevate urinary coproporphyrin III** levels, making it distinguishable from lead toxicity through this biomarker.
Question 152: A neonate was brought to the hospital with chief complaints of poor feeding, vomiting, acidosis, and cataract. Benedict's test on urine was positive, but urinary glucose was negative. What is the defective enzyme in the above-mentioned disorder?
- A. Galactose 1-phosphate uridyl transferase (Correct Answer)
- B. Fructokinase
- C. Lactase
- D. Sucrase
- E. Aldolase B
Explanation: ***Galactose 1-phosphate uridyl transferase*** - This enzyme deficiency leads to **classic galactosemia**, characterized by the accumulation of **galactose-1-phosphate**, which is toxic. - Clinical features like **poor feeding, vomiting, acidosis, and cataracts** are typical, and a positive **Benedict's test** (detecting reducing sugars like galactose) with negative urinary glucose confirms the presence of another reducing sugar. *Fructokinase* - Deficiency of fructokinase causes **essential fructosuria**, a benign condition where **fructose** accumulates in the urine. - Unlike classic galactosemia, it does not present with severe symptoms like **acidosis** or **cataracts**. *Aldolase B* - **Aldolase B deficiency** causes hereditary fructose intolerance, presenting with **vomiting, hypoglycemia, and hepatomegaly** after fructose ingestion. - It does not cause **cataracts**, and Benedict's test would detect fructose, but the clinical context (symptoms with fructose/sucrose intake) differs from galactosemia. *Lactase* - **Lactase deficiency** (lactose intolerance) results in gastrointestinal symptoms such as **bloating, diarrhea, and abdominal pain** upon lactose consumption. - It does not typically cause **acidosis, cataracts**, or a positive Benedict's test in urine unless secondary bacterial fermentation leads to other reducing substances. *Sucrase* - **Sucrase-isomaltase deficiency** leads to the malabsorption of sucrose, causing symptoms similar to lactose intolerance like **diarrhea and abdominal cramping**. - It does not result in the systemic, severe metabolic derangements or signs like **cataracts** seen in classic galactosemia.
Question 153: A patient presents with a skin rash that is exaggerated on sun exposure. What is the repair mechanism involved in this condition?
- A. Nucleotide excision repair (Correct Answer)
- B. Base excision repair
- C. Mismatch repair
- D. Double stranded DNA break repair
Explanation: ***Nucleotide excision repair*** - This mechanism is responsible for repairing **bulky lesions** in DNA, such as **pyrimidine dimers** caused by **UV radiation** from sun exposure. - Patients with defects in nucleotide excision repair (e.g., **xeroderma pigmentosum**) are highly sensitive to sunlight and develop skin rashes, pigment changes, and skin cancers. *Base excision repair* - This pathway primarily corrects **small damaged bases** that do not cause significant distortion of the DNA helix, such as deaminated, oxidized, or alkylated bases. - It does not primarily address the bulky lesions induced by UV light that cause exaggerated sun sensitivity. *Mismatch repair* - This system corrects errors, like **mismatched base pairs**, that are incorporated during DNA replication. - It is not directly involved in repairing DNA damage caused by environmental factors like UV radiation. *Double stranded DNA break repair* - This mechanism repairs **double-strand breaks** in DNA, which are highly deleterious lesions caused by ionizing radiation or oxidative stress. - While critical for genome stability, it is not the primary repair pathway for UV-induced DNA lesions or the direct cause of sun sensitivity.
Question 154: A 45-year-old patient presents with joint pain and weakness and is known to have homocystinuria. Which vitamin is required in the treatment?
- A. Vitamin B6 (Correct Answer)
- B. Vitamin B12
- C. Vitamin B7
- D. Vitamin B1
- E. Vitamin B9
Explanation: ***Vitamin B6*** - **Homocystinuria** is often caused by a deficiency in the enzyme **cystathionine beta-synthase**, which requires **pyridoxal phosphate (active form of B6)** as a cofactor. - Supplementation with high-dose **vitamin B6** can help some patients by increasing the residual activity of the enzyme, thereby reducing **homocysteine levels**. - This is the **primary treatment** for **B6-responsive homocystinuria** (approximately 50% of cases respond to B6 therapy). *Vitamin B12* - Vitamin B12 is a cofactor for the enzyme **methionine synthase**, which converts homocysteine back to methionine. - While it plays a role in homocysteine metabolism, **vitamin B6** is typically the primary treatment for homocystinuria caused by **cystathionine beta-synthase deficiency**. *Vitamin B9* - Vitamin B9 (folic acid) works together with **vitamin B12** as a cofactor in the **remethylation pathway** via methionine synthase. - While folate supplementation may help lower homocysteine levels, it is **not the primary treatment** for classical homocystinuria due to cystathionine beta-synthase deficiency. - **Vitamin B6** remains the first-line vitamin therapy for enzyme deficiency-related homocystinuria. *Vitamin B7* - Vitamin B7, or **biotin**, is a cofactor for carboxylase enzymes and is involved in fatty acid synthesis and gluconeogenesis. - It has no direct role in the metabolism of **homocysteine** or the treatment of homocystinuria. *Vitamin B1* - Vitamin B1, or **thiamine**, is essential for carbohydrate metabolism and nerve function. - It is not involved in the metabolic pathways that regulate **homocysteine levels** or the treatment of homocystinuria.
Question 155: A patient came to the hospital with severe abdominal pain, and lipase levels were elevated. On imaging, a stone is found in the common bile duct (CBD). Which enzyme is most likely elevated in this condition?
- A. ALT
- B. GGT
- C. LDH
- D. AST
- E. ALP (Correct Answer)
Explanation: ***ALP (Alkaline Phosphatase)*** - **ALP** is the **most characteristic enzyme elevation** in **biliary obstruction** from a CBD stone. - ALP is found in high concentrations in the **bile duct epithelium** and hepatocytes adjacent to bile ducts, and rises dramatically with **cholestasis** and **obstructive jaundice**. - In CBD stone obstruction, ALP typically rises **3-10 times normal**, making it the hallmark biochemical marker of this condition. - While lipase is elevated due to associated pancreatitis, **ALP elevation specifically indicates the biliary obstruction**. *GGT (Gamma-Glutamyl Transferase)* - **GGT** is also elevated in **cholestasis** and **bile duct obstruction**. - GGT often rises in parallel with ALP and helps confirm the hepatobiliary origin of ALP elevation (vs. bone source). - However, **ALP is more specific** and typically shows greater magnitude of elevation in acute CBD obstruction, making it the **most likely** elevated enzyme in this clinical context. *ALT (Alanine Aminotransferase)* - **ALT** may be **mildly to moderately elevated** if there is secondary hepatocellular injury from biliary obstruction. - However, ALT primarily indicates **hepatocyte damage** rather than cholestasis, and its elevation is typically **less pronounced** than ALP in obstructive biliary disease. - The pattern in CBD obstruction is **cholestatic** (high ALP) rather than **hepatocellular** (high ALT). *AST (Aspartate Aminotransferase)* - **AST** can be elevated in various conditions including liver, heart, and muscle damage. - Like ALT, it may show mild elevation in biliary obstruction but is **not the primary marker**. - AST is less specific than ALP for diagnosing CBD stone obstruction. *LDH (Lactate Dehydrogenase)* - **LDH** is a **non-specific marker** of tissue damage found in multiple organs. - While it may be elevated, it provides little diagnostic value when specific markers like **ALP and lipase** are available. - LDH does not help differentiate biliary obstruction from other causes of abdominal pain.
Dermatology
1 questionsA patient who has always neglected his nutrition presented with follicular hyperkeratosis on the extensor aspect of the forearm. What is the diagnosis?
NEET-PG 2024 - Dermatology NEET-PG Practice Questions and MCQs
Question 151: A patient who has always neglected his nutrition presented with follicular hyperkeratosis on the extensor aspect of the forearm. What is the diagnosis?
- A. Phrynoderma (Correct Answer)
- B. Eruptive xanthoma
- C. Darier's disease
- D. Folliculitis
Explanation: ***Phrynoderma*** - **Phrynoderma**, also known as **toad skin**, is characterized by **follicular hyperkeratosis**, particularly on the **extensor surfaces** of limbs like the forearm. - This condition is closely linked to **nutritional deficiencies**, often involving **vitamin A**, **essential fatty acids**, or sometimes **B vitamins**. *Eruptive xanthoma* - **Eruptive xanthomas** are small, yellow-red papules that often appear suddenly, typically on the **buttocks**, **extensor surfaces of the limbs**, and **trunk**. - They are a cutaneous manifestation of **severe hypertriglyceridemia** and not primarily related to general nutritional neglect or follicular hyperkeratosis. *Darier's disease* - **Darier's disease** is a **rare, inherited genetic disorder** characterized by greasy, crusted papules primarily in **seborrheic areas** such as the scalp, forehead, chest, and groin. - It results from a mutation in the **ATP2A2 gene**, affecting calcium signaling in keratinocytes, and is not a nutritional deficiency condition. *Folliculitis* - **Folliculitis** is the inflammation of one or more **hair follicles**, often caused by **bacterial** (e.g., *Staphylococcus aureus*) or **fungal infections**. - It presents as small, red, sometimes pus-filled bumps around hair follicles, distinct from the dry, rough texture of follicular hyperkeratosis seen in phrynoderma.
Pathology
1 questionsThe diagrammatic representation of the karyotype of an individual indicates a specific genetic abnormality. What is the diagnosis?
NEET-PG 2024 - Pathology NEET-PG Practice Questions and MCQs
Question 151: The diagrammatic representation of the karyotype of an individual indicates a specific genetic abnormality. What is the diagnosis?
- A. Angelman syndrome
- B. Cri du Chat syndrome
- C. DiGeorge syndrome
- D. Prader-Willi syndrome (Correct Answer)
Explanation: ***Prader-Willi syndrome*** - The karyotype shows an abnormality on **chromosome 15**, which is consistent with Prader-Willi syndrome caused by **deletion of 15q11-q13** inherited from the **paternal** chromosome or **maternal uniparental disomy**. - While PWS deletions are typically **submicroscopic**, larger deletions can occasionally be visible on standard karyotyping, particularly when they represent **class I deletions** that are more extensive and involve additional chromosomal material beyond the typical PWS critical region. *Angelman syndrome* - Although Angelman syndrome also involves **chromosome 15q11-q13 deletion**, it results from **maternal** deletion or **paternal uniparental disomy**, and presents with distinctly different clinical features. - Clinical presentation includes **severe intellectual disability**, **ataxia**, **seizures**, **absent speech**, and **inappropriate laughter** (happy demeanor), which differs significantly from the PWS phenotype. *DiGeorge syndrome* - DiGeorge syndrome is caused by **deletion of chromosome 22q11.2**, not chromosome 15 as shown in the karyotype. - Clinical features include **cardiac defects** (conotruncal abnormalities), **thymic hypoplasia**, **parathyroid hypoplasia** (hypocalcemia), **cleft palate**, and characteristic facial features (CATCH-22 syndrome). *Cri du Chat syndrome* - This syndrome results from **deletion of chromosome 5p** (short arm of chromosome 5), not chromosome 15 as indicated in the karyotype. - Characteristic features include **high-pitched cry** resembling a cat's meow in infancy, **intellectual disability**, **microcephaly**, and **distinctive facial features**.
Pediatrics
1 questionsA 13-year-old boy presents with jaundice, fatigue, muscle stiffness, tremors, and behavioral changes. Examination reveals an enlarged liver and spleen. A Kayser-Fleischer ring was noted. What is the definitive diagnostic test?
NEET-PG 2024 - Pediatrics NEET-PG Practice Questions and MCQs
Question 151: A 13-year-old boy presents with jaundice, fatigue, muscle stiffness, tremors, and behavioral changes. Examination reveals an enlarged liver and spleen. A Kayser-Fleischer ring was noted. What is the definitive diagnostic test?
- A. Urinary copper
- B. Serum ceruloplasmin
- C. Hepatic parenchymal copper concentration (Correct Answer)
- D. Slit lamp examination
- E. Genetic testing for ATP7B mutation
Explanation: ***Hepatic parenchymal copper concentration*** - This is considered the **gold standard** for diagnosing **Wilson's disease**, as it directly measures the accumulation of copper in the liver, which is the hallmark of the condition. - A concentration of **>250 mcg/g of dry liver weight** is diagnostic of Wilson's disease, irrespective of other laboratory findings. *Urinary copper* - While **elevated 24-hour urinary copper excretion** is a common finding in Wilson's disease, it can also be influenced by other conditions and may not always be definitively diagnostic on its own. - It is a **screening tool** and part of the diagnostic workup, but not the definitive diagnostic test as it's an indirect measure of copper overload. *Serum ceruloplasmin* - **Low serum ceruloplasmin levels** are characteristic of Wilson's disease because ceruloplasmin is the primary copper-carrying protein in the blood. - However, ceruloplasmin levels can be **normal in some Wilson's patients**, especially those presenting with hepatic manifestations, and can be low in other conditions like severe liver failure or malabsorption. *Slit lamp examination* - A **slit lamp examination** is used to identify **Kayser-Fleischer rings**, which are corneal copper deposits. - While their presence is highly suggestive of Wilson's disease, especially with neurological symptoms, they **may be absent in up to 30-50% of patients** with hepatic-only presentations, and their absence does not rule out the disease. *Genetic testing for ATP7B mutation* - **Molecular genetic testing** can identify mutations in the ATP7B gene, which encodes the copper-transporting ATPase. - While highly specific for confirming Wilson's disease and useful for family screening, it is a **confirmatory test** rather than the definitive diagnostic test, as over 500 different mutations exist and not all are identified in routine testing. - Hepatic copper measurement remains the diagnostic standard as it directly demonstrates the pathophysiologic defect.
Pharmacology
2 questionsA patient with a history of binge alcohol intake presented to the emergency department with convulsions, altered sensorium, and a plasma glucose level of $45 \mathrm{mg} / \mathrm{dL}$. Which of the following treatments is needed?
Methotrexate use causes reduced synthesis of which of the following?
NEET-PG 2024 - Pharmacology NEET-PG Practice Questions and MCQs
Question 151: A patient with a history of binge alcohol intake presented to the emergency department with convulsions, altered sensorium, and a plasma glucose level of $45 \mathrm{mg} / \mathrm{dL}$. Which of the following treatments is needed?
- A. Thiamine
- B. $25 \% $ Dextrose
- C. Thiamine followed by Dextrose (Correct Answer)
- D. Fomepizole
- E. Glucagon
Explanation: ***Thiamine followed by Dextrose*** - In patients with **alcoholism** and suspected **hypoglycemia**, thiamine should always be administered before or concurrently with dextrose to prevent **Wernicke encephalopathy**. - Dextrose alone can precipitate or worsen Wernicke encephalopathy in **thiamine-deficient** individuals by increasing carbohydrate metabolism, thereby depleting residual thiamine. *Thiamine* - While **thiamine** is crucial for patients with chronic alcohol intake, administering it alone will not immediately resolve the **hypoglycemia** and associated neurological symptoms like convulsions and altered sensorium. - Thiamine is essential to prevent complications like **Wernicke-Korsakoff syndrome**, but the immediate life-threatening issue is the low blood glucose. *25% Dextrose* - Administering **dextrose** alone to an **alcohol-dependent** patient is risky because it can precipitate or worsen **Wernicke's encephalopathy** by increasing glucose metabolism without adequate thiamine. - While dextrose will correct the **hypoglycemia**, its administration without prior thiamine is contraindicated in this patient population. *Glucagon* - **Glucagon** works by mobilizing hepatic glycogen stores to raise blood glucose levels. - In patients with **chronic alcohol intake**, hepatic glycogen stores are often **depleted**, making glucagon ineffective. - Additionally, glucagon has a **slower onset** compared to intravenous dextrose, making it unsuitable for this emergency situation with convulsions and altered sensorium. *Fomepizole* - **Fomepizole** is an antidote used in cases of **methanol** or **ethylene glycol poisoning** to inhibit alcohol dehydrogenase. - It is not indicated for treating **alcohol withdrawal**, **hypoglycemia**, or related complications in patients with binge alcohol intake.
Question 152: Methotrexate use causes reduced synthesis of which of the following?
- A. TMP (Correct Answer)
- B. CMP
- C. GMP
- D. AMP
- E. UMP
Explanation: ***TMP (Thymidylate)*** - Methotrexate is a **folate analog** that inhibits **dihydrofolate reductase (DHFR)**, preventing the regeneration of tetrahydrofolate (THF) from dihydrofolate. - **Tetrahydrofolate** is essential for **thymidylate synthase**, which converts dUMP to **TMP (thymidylate)** - this is the **most directly and significantly affected** nucleotide synthesis pathway. - Reduced TMP synthesis leads to impaired DNA synthesis and is the **primary mechanism** of methotrexate's cytotoxic effects. *CMP (Cytidine monophosphate)* - CMP synthesis occurs via the **de novo pyrimidine pathway** starting from carbamoyl phosphate and aspartate, forming UMP, which is then converted to CMP. - This pathway **does not require tetrahydrofolate** cofactors, so methotrexate does not significantly affect CMP synthesis directly. *GMP (Guanosine monophosphate)* - GMP is a purine nucleotide whose synthesis **does require tetrahydrofolate** derivatives (N10-formyl-THF) at two steps in the de novo purine pathway. - However, the effect on GMP is **less direct and less pronounced** than on TMP synthesis, and cells can partially compensate through salvage pathways. *AMP (Adenosine monophosphate)* - AMP is also a purine nucleotide that requires **N10-formyl-THF** cofactors during de novo synthesis (same pathway branch point as GMP). - Like GMP, it is affected but **less directly than TMP**, and salvage pathways provide alternative synthesis routes. *UMP (Uridine monophosphate)* - UMP is synthesized through the **de novo pyrimidine pathway** which does not require folate cofactors. - Methotrexate does not inhibit the enzymes (carbamoyl phosphate synthetase II, aspartate transcarbamoylase, dihydroorotase, etc.) involved in UMP synthesis.