Vitamin A and Vision — MCQs
During the dark phase of visual cycle, which form of vitamin A combines with opsin to make Rhodopsin:
Thiamine deficiency is best diagnosed by?
At what age does a child typically know their full name?
Pseudo tumor cerebri is caused by?
A child of 8 kg has Bitot's spots in both eyes. Which of the following is the most appropriate schedule to prescribe vitamin A to this child?
A patient complained of gradual diminution of vision. On examination, the patient had dry eyes and a rough corneal surface. What deficiency is most likely causing these manifestations?
Match the following: A) Caplan syndrome- 1) Found first in coal worker B) Asbestosis- 2) Upper lobe predominance C) Mesothelioma- 3) Involves lower lobe D) Sarcoidosis- 4) Pleural effusion is seen
Name the enzyme involved in this cycle:
All of the following are water-soluble antioxidants except?
A patient presents with recurrent oral lesions and eye redness as shown in the images below. The patient also complains of chronic diarrhea and abdominal discomfort. Which test is recommended for this patient?
Vitamin A and Vision Indian Medical PG Practice Questions and MCQs
Question 1: During the dark phase of visual cycle, which form of vitamin A combines with opsin to make Rhodopsin:
- A. 11-cis-Retinaldehyde (Correct Answer)
- B. 11-cis-Retinol
- C. All trans-Retinol
- D. All trans-Retinaldehyde
Explanation: ***11-cis-Retinaldehyde*** - In the **dark phase** of the visual cycle, **11-cis-retinaldehyde** (retinal) is regenerated and combines with **opsin** to form **rhodopsin**. - This molecule is crucial for initiating the visual transduction pathway in **rod cells** when light is detected. *11-cis-Retinol* - **11-cis-Retinol** is an intermediate in the regeneration of 11-cis-retinaldehyde from all-trans-retinol, but it does not directly bind to opsin to form rhodopsin. - It is converted to 11-cis-retinaldehyde by the enzyme **11-cis-retinol dehydrogenase**. *all trans-Retinol* - **All-trans-retinol** is the form of vitamin A transported to the eye and is also an intermediate in the visual cycle, but it does not combine directly with opsin. - It is converted to all-trans-retinaldehyde after the absorption of light and then subsequently isomerized to 11-cis-retinol. *All trans-Retinaldehyde* - **All-trans-retinaldehyde** is formed when **rhodopsin** absorbs light, causing the isomerization of 11-cis-retinaldehyde. - This molecule is then released from opsin and subsequently reduced to all-trans-retinol before being recycled back to 11-cis-retinaldehyde in the pigment epithelium.
Question 2: Thiamine deficiency is best diagnosed by?
- A. Blood thiamine level
- B. Transketolase activity in blood (Correct Answer)
- C. Aldolase activity in blood
- D. Urinary thiamine level
Explanation: ***Transketolase activity in blood*** - **Transketolase** is a thiamine pyrophosphate (TPP)-dependent enzyme, and its activity in red blood cells is considered the **gold standard** for assessing thiamine status. - A **decrease in transketolase activity** that improves after the addition of TPP in vitro (TPP effect) is highly indicative of thiamine deficiency. *Blood thiamine level* - While a direct measure, **blood thiamine levels** can be influenced by recent dietary intake and may not accurately reflect the body's overall thiamine stores or functional deficiency. - Furthermore, measuring total blood thiamine doesn't always correlate well with the **functional status** of thiamine-dependent enzymes. *Aldolase activity in blood* - **Aldolase** is an enzyme involved in glycolysis, but its activity is **not dependent on thiamine**. - Therefore, measuring aldolase activity provides no information regarding thiamine status. *Urinary thiamine level* - **Urinary thiamine levels** primarily reflect recent thiamine intake and renal excretion rather than the body's total thiamine stores or a functional deficiency. - Low urinary thiamine can suggest deficiency, but it's **less reliable** than functional assays.
Question 3: At what age does a child typically know their full name?
- A. 15 months
- B. 24 months
- C. 36 months (Correct Answer)
- D. 48 months
Explanation: ***36 months*** - By **36 months old** (3 years), most children can clearly state their **full name** (first and last name) when asked. - This milestone indicates developing **self-awareness** and **language skills**. - This is a standard developmental milestone tested in CDC and AAP guidelines. *15 months* - At **15 months**, children typically know their **first name** and respond to it, but cannot state their full name. - Their language at this age often includes only a few single words with primarily receptive understanding. *24 months* - By **24 months** (2 years), children often use two-to-four-word sentences and can identify familiar objects and people. - While they know their first name and may start recognizing it, they usually cannot articulate their full name yet. *48 months* - At **48 months** (4 years), a child's language skills are much more advanced, and they can typically tell stories and engage in complex conversations. - Knowing their full name is an expected milestone that should have been achieved earlier, typically by 36 months.
Question 4: Pseudo tumor cerebri is caused by?
- A. Vitamin B1 excess
- B. Vitamin D excess
- C. Vitamin E excess
- D. Vitamin A excess (Correct Answer)
Explanation: ***Vitamin A excess*** - **Hypervitaminosis A**, or excess vitamin A, is a known cause of **pseudotumor cerebri** (also called **idiopathic intracranial hypertension**). - This condition involves increased **intracranial pressure**, often without an obvious structural cause. *Vitamin B1 excess* - Excess intake of **vitamin B1 (thiamine)** is generally considered benign and is not known to cause pseudotumor cerebri. - Thiamine is a **water-soluble vitamin**, and excess amounts are typically excreted in urine. *Vitamin D excess* - **Vitamin D toxicity** primarily leads to **hypercalcemia**, which can cause kidney stones, bone pain, and gastrointestinal symptoms. - While it can have neurological effects due to hypercalcemia, it typically does not directly cause pseudotumor cerebri. *Vitamin E excess* - **Vitamin E excess** can interfere with **blood clotting** and may increase the risk of bleeding, especially in individuals taking anticoagulants. - There is no established link between hypervitaminosis E and the development of pseudotumor cerebri.
Question 5: A child of 8 kg has Bitot's spots in both eyes. Which of the following is the most appropriate schedule to prescribe vitamin A to this child?
- A. 2 lakh units orally on day 0, 14
- B. 2 lakh units orally on day 0, 1, 14 (Correct Answer)
- C. 1 lakh units orally on day 0, 14
- D. 1 lakh units orally on day 0, 1, 14
Explanation: ***2 lakh units orally on day 0, 1, 14*** - For a child weighing **8 kg** with **Bitot's spots (WHO classification X1B)**, the therapeutic dose is **200,000 IU** (2 lakh units) of vitamin A. - The standard WHO/IAP schedule for treating **vitamin A deficiency with ocular signs** is administration on **Day 0, Day 1, and Day 14** to rapidly replete stores and prevent progression. - The **oral route** is preferred for **Bitot's spots without corneal ulceration**, as it is effective, safe, and well-tolerated. - **IM route** is reserved for severe xerophthalmia (X2/X3 with corneal ulceration), persistent vomiting, or inability to take oral medications. *2 lakh units orally on day 0, 14* - Although the individual dose of **200,000 IU** is correct for this 8 kg child with **Bitot's spots**, this schedule misses the critical **Day 1 dose**. - The missing dose on Day 1 delays rapid **vitamin A replenishment**, which is crucial for preventing progression of **ocular damage** and achieving adequate tissue stores. *1 lakh units orally on day 0, 14* - This dose of **100,000 IU** is inadequate for a child weighing **8 kg or more** with clinical **vitamin A deficiency**. - WHO guidelines recommend **100,000 IU for children <8 kg** and **200,000 IU for children ≥8 kg**, making this dosage insufficient. - Additionally, the schedule is incomplete as it misses the **Day 1 dose**. *1 lakh units orally on day 0, 1, 14* - While the schedule of Day 0, Day 1, and Day 14 is appropriate, the **dose of 100,000 IU is inadequate** for a child weighing **8 kg**. - This lower dose may not provide sufficient **vitamin A replenishment** to reverse **Bitot's spots** and prevent progression to more severe xerophthalmia.
Question 6: A patient complained of gradual diminution of vision. On examination, the patient had dry eyes and a rough corneal surface. What deficiency is most likely causing these manifestations?
- A. Iron
- B. Protein
- C. Niacin
- D. Vitamin A (Correct Answer)
Explanation: ***Vitamin A*** - **Vitamin A deficiency** is a common cause of **xerophthalmia**, characterized by **dry eyes** (**xerosis conjunctivae**) and roughening of the **cornea** due to impaired mucin production [1]. In vitamin A deficiency, mucus-secreting cells are replaced by keratin-producing cells [2]. - Progression of ocular epithelial keratinization can lead to **Bitot's spots**, corneal ulceration, and ultimately **blindness** [1], [2]. *Iron* - **Iron deficiency** primarily leads to **iron-deficiency anemia**, causing fatigue, pallor, and weakness, but not directly ocular manifestations like dry eyes or rough cornea. - While severe anemia can cause some visual disturbances, it does not typically present with the specific **xerophthalmic** changes seen here. *Protein* - **Protein deficiency** can lead to conditions like **kwashiorkor** (edema, muscle wasting) or **marasmus** (severe wasting), which broadly impair health and immunity. - However, it does not directly cause the specific ocular signs of **dryness** and **corneal roughening** as a primary deficiency, though it can exacerbate other nutritional deficiencies. *Niacin* - **Niacin (Vitamin B3) deficiency** causes **pellagra**, characterized by the "3 Ds": **dermatitis**, **diarrhea**, and **dementia**. - Ocular symptoms are not a common or primary feature of niacin deficiency; it does not cause **dry eyes** or **corneal roughening**.
Question 7: Match the following: A) Caplan syndrome- 1) Found first in coal worker B) Asbestosis- 2) Upper lobe predominance C) Mesothelioma- 3) Involves lower lobe D) Sarcoidosis- 4) Pleural effusion is seen
- A. A-3, B-4, C-2, D-1
- B. A-1, B-4, C-3, D-2 (Correct Answer)
- C. A-4, B-2, C-3, D-1
- D. A-2, B-4, C-3, D-1
Explanation: **A-1, B-4, C-3, D-2** - **Caplan syndrome** was first described in **coal workers** with **rheumatoid arthritis** and progressive massive fibrosis. - **Asbestosis** is often associated with **pleural effusion**, which can be benign or malignant. - **Mesothelioma** typically involves the **lower lobes** of the lungs, specifically the pleura, and is strongly linked to asbestos exposure. - **Sarcoidosis** is characterized by **non-caseating granulomas**, which have a predilection for the **upper lobes** of the lungs. *A-3, B-4, C-2, D-1* - This option incorrectly states that Caplan syndrome involves the lower lobe; **Caplan syndrome** is defined by the presence of large nodules in the lungs of coal workers with rheumatoid arthritis, and their specific lobar distribution is not a defining characteristic. - This option incorrectly states that Mesothelioma has an upper lobe predominance; **Mesothelioma** is a pleural malignancy and typically involves the **lower lobes**, extending along the pleura. *A-4, B-2, C-3, D-1* - This option incorrectly associates Caplan syndrome with pleural effusion; **Caplan syndrome** manifests as rheumatoid nodules in the lungs, not primarily pleural effusion. - This option incorrectly states that Asbestosis has an upper lobe predominance; **Asbestosis** predominantly affects the **lower lobes** of the lungs, causing interstitial fibrosis. *A-2, B-4, C-3, D-1* - This option incorrectly states that Caplan syndrome has an upper lobe predominance; the defining feature of **Caplan syndrome** is the combination of rheumatoid arthritis and pneumoconiosis, not specific lobar involvement. - This option correctly identifies pleural effusion with asbestosis and lower lobe involvement with mesothelioma, but **Caplan syndrome** is not characterized by upper lobe predominance.
Question 8: Name the enzyme involved in this cycle:
- A. Retinal isomerase (Correct Answer)
- B. Retinol isomerase
- C. Transducin
- D. Gustducin
Explanation: ***Retinal isomerase*** - This enzyme is crucial for the regeneration of **11-cis-retinal** from **all-trans-retinal** in the visual cycle. - It catalyzes the **isomerization** process, which is essential for rhodopsin to be reformed and ready to detect light again. *Retinol isomerase* - This term is a misnomer; the substrate that undergoes isomerization is retinal, not retinol. - While **retinol** is a precursor to retinal, it doesn't directly undergo the isomerization step that is vital for the visual cycle. *Transducin* - **Transducin** is a **G-protein** involved in signal transduction after light activates rhodopsin. - It binds to activated rhodopsin, triggering a cascade that ultimately leads to changes in membrane potential, but it is not an isomerase enzyme. *Gustducin* - **Gustducin** is a **G-protein** primarily involved in the **sensation of taste**, specifically bitter and sweet tastes. - It plays no role in the visual cycle or the isomerization of retinal.
Question 9: All of the following are water-soluble antioxidants except?
- A. uric acid
- B. Polyphenols
- C. Carotenes (Correct Answer)
- D. Ascorbate
Explanation: ***Carotenes*** - **Carotenes** are **lipid-soluble** antioxidants that are typically found in cell membranes and lipid components of the body. - They protect against **lipid peroxidation**, which is damage to cellular membranes caused by free radicals. *Ascorbate* - **Ascorbate** (Vitamin C) is a well-known **water-soluble** antioxidant that readily donates electrons to neutralize free radicals in aqueous environments. - It plays a crucial role in regenerating other antioxidants, such as **alpha-tocopherol (Vitamin E)**. *Uric acid* - **Uric acid** is a potent **water-soluble** antioxidant present in high concentrations in the plasma. - It scavenges various reactive oxygen species and reactive nitrogen species, especially in the **extracellular fluid**. *Polyphenols* - **Polyphenols** are a large group of **water-soluble** compounds found in plants that act as antioxidants. - They reduce oxidative stress by **scavenging free radicals**, chelating metal ions, and inhibiting enzymes involved in radical generation.
Question 10: A patient presents with recurrent oral lesions and eye redness as shown in the images below. The patient also complains of chronic diarrhea and abdominal discomfort. Which test is recommended for this patient?
- A. Anti-endothelial cell antibodies
- B. Anti-endomysial antibodies (Correct Answer)
- C. RBC glutathione reductase levels
- D. Serum methylmalonic acid levels
Explanation: ***Anti-endomysial antibodies*** - The image on the left shows **aphthous stomatitis**, and the one on the right shows **conjunctivitis** with dilated vessels. These two findings, along with other potential symptoms (e.g., GI, arthritis), could indicate **celiac disease**. - **Anti-endomysial antibodies** are highly specific for **celiac disease**, which can manifest with extraintestinal symptoms including recurrent aphthous stomatitis and, less commonly, ocular symptoms. *Anti-endothelial cell antibodies* - These antibodies are associated with **vasculitis** and other autoimmune conditions that primarily affect blood vessels. - While some vasculitides can cause ocular inflammation and oral lesions, they don't typically present with the specific combination and appearance of symptoms seen here. *RBC glutathione reductase levels* - This test measures the activity of the enzyme **glutathione reductase** in red blood cells. - It is primarily used to assess **riboflavin (vitamin B2) deficiency** and has no direct relevance to the conditions suggested by the visual findings. *Serum methylmalonic acid levels* - Elevated **serum methylmalonic acid (MMA)** levels are a sensitive indicator of **vitamin B12 deficiency**. - While vitamin B12 deficiency can cause glossitis (inflammation of the tongue), it doesn't typically cause aphthous stomatitis or conjunctivitis.
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