Clinical Cases of Vitamins

Case Scenario 1:

A 5-year-old child from a rural area is brought to the ophthalmology clinic with complaints of difficulty seeing at night for the past few months. On examination, the child has dry, rough conjunctiva, Bitot’s spots, and dry, scaly skin.

OR

Case Scenario 2:

A 14-year-old boy had a problem with vision at night. However, his vision was quite normal during the day time except when he entered a dimly lit room (such as a movie hall). On investigation, his plasma retinol levels were found to be low.

a) What is the most likely nutritional deficiency in this child? Name two dietary sources of this nutrient.
b) Explain the biochemical and physiological roles of this vitamin in vision and epithelial integrity.
c) What are the consequences of excess intake of this vitamin?

Answer:

a) The child is suffering from Vitamin A deficiency.

Dietary sources:
— Animal sources: liver, egg yolk, butter, cod liver oil.
— Plant sources: carrots, papaya, mango, dark green leafy vegetables.

b) Role in vision (visual cycle):

In rod cells of the retina, 11-cis-retinal (a derivative of vitamin A) combines with opsin to form rhodopsin.

Rhodopsin is essential for scotopic (dim-light) vision.

Light converts rhodopsin to all-trans-retinal, triggering nerve impulses.

Other Functions of Vitamin A:

• • • Maintains cell health (epithelial cells): maintenance of proper immune system.
    • Cell growth & differentiation.
    • Cardiovascular disease prevention: carotene prevents heart attacks.
    • Cancer (by free radicals &oxidants) prevention as Carotenoids act as antioxidants.
    • Synthesis of Transferrin, Glycoproteins

c) Hypervitaminosis A (excess intake):

Symptoms: headache, nausea, vomiting, irritability, skin desquamation, hepatotoxicity, bone pain, and pseudotumor cerebri.

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Case Scenario 3:

A 2-year-old child is brought to the pediatric clinic with bowing of the legs and delayed walking. On examination, the child has widened wrists, prominent costochondral junctions (rachitic rosary), and frontal bossing. X-ray of the wrist shows cupping and fraying of the metaphyses.

OR

Case Scenario 4:

A 10-year-old girl child presents to her primary care physician with complaints of generalized fatigue, muscle weakness, and bone pain. She reports that she spends most of her time indoors due to her office job. She also mentions that she follows a vegetarian diet and does not consume dairy products.

a) What is the most probable diagnosis? Name two dietary sources of the deficient nutrient.
b) Explain the biochemical role of vitamin D in calcium and phosphate homeostasis.
c) What are the manifestations of vitamin D toxicity?

Answer:

a) The child has rickets due to vitamin D deficiency.

• • Dietary sources:
    — Animal sources: fish liver oils, egg yolk, butter, liver.
    — Fortified foods and sunlight (skin synthesis of cholecalciferol).

b) Biochemical role of vitamin D:

• • Active form of vitamin D (1,25-dihydroxycholecalciferol or calcitriol) is synthesized in the kidney.
  • It increases intestinal absorption of calcium and phosphate by inducing synthesis of calcium-binding proteins in the gut.
  • Promotes bone mineralization by maintaining adequate serum calcium and phosphate levels.
  • Stimulates osteoblasts to secrete factors that activate osteoclasts when calcium is very low.

c) Vitamin D toxicity (hypervitaminosis D):

• • Excess intake can cause hypercalcemia, leading to:
    — Nausea, vomiting, constipation.
    — Calcification of soft tissues (kidneys, heart, lungs).
    — Polyuria, polydipsia, and renal damage.

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Case Scenario 5:

A 25-year-old bachelor, consuming mainly bread, cheese, boiled eggs, milk, and canned food (lacking fresh fruits and vegetables) for several months, develops small red spots (petechiae) on his legs, swollen and bleeding gums, tender swollen joints, melena (blood in stools), and is found to be anemic.

a) Interpret the case and name the deficient vitamin.
b) Write the functions, daily requirement, absorption, and deficiency manifestations of this vitamin.
c) Explain the specific role of this vitamin in collagen synthesis.

Answer:

a) The case is scurvy, due to deficiency of vitamin C (ascorbic acid).

b) –

✅ Functions of vitamin C:

• • Hydroxylation of proline and lysine in collagen synthesis.
  • Antioxidant and free radical scavenger.
  • Enhances absorption of non-heme iron.
  • Required for synthesis of certain neurotransmitters and carnitine.
  • Immune system support.

✅ Daily requirement:

• • Adults: ~75–90 mg/day (higher in smokers, pregnant or lactating women).

✅ Absorption:

• • Absorbed in the small intestine (jejunum) by active transport when intake is low, and passive diffusion at high doses.

✅ Deficiency manifestations:

• • Scurvy: bleeding gums, petechiae, poor wound healing, joint pain, bone fragility, anemia.

c)

• • In collagen synthesis, vitamin C is a cofactor for prolyl and lysyl hydroxylases, which hydroxylate proline and lysine residues in collagen.
  • Hydroxylation is essential for cross-linking collagen fibrils, providing strength and stability to connective tissue.

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Case Scenario 6:

A 25-year-old woman presents with breathlessness, palpitations, generalized edema, muscle weakness, difficulty walking, and inability to stand from a squatting position. Examination reveals a rapid, bounding pulse, elevated systolic BP, and low diastolic BP. She has been consuming only ultra-refined, polished rice for 2 years and avoiding pulses, nuts, and oilseeds for weight loss.

a) Interpret the case and name the deficient vitamin.
b) Mention the features which supports this diagnosis.

c) Mention the functions, daily requirement, and deficiency manifestations of this vitamin.

Answer:

a) The woman has Wet beriberi due to deficiency of vitamin B1 (thiamine).

b) Symptoms suggestive of cardiac involvement:

• • Breathlessness
  • Palpitations
  • Generalized edema
  • Rapid, bounding pulse
  • Wide pulse pressure (↑ systolic, ↓ diastolic BP)

c)✅ Functions of thiamine:

• • Coenzyme as thiamine pyrophosphate (TPP) for:
    • Pyruvate dehydrogenase (pyruvate → acetyl-CoA)
    • α-ketoglutarate dehydrogenase (TCA cycle)
    • Transketolase (HMP shunt)
    • Branched-chain ketoacid dehydrogenase

✅ Daily requirement:

• • Adults: ~1–1.5 mg/day (higher in pregnancy, lactation, high carbohydrate diet).

✅ Deficiency manifestations:

• • Wet beriberi: cardiac failure, edema, high-output heart failure (explains rapid pulse, BP findings).
  • Dry beriberi: peripheral neuropathy, muscle weakness, difficulty walking, foot/wrist drop.
  • Wernicke-Korsakoff syndrome (in alcoholics): confusion, ataxia, ophthalmoplegia, memory loss.

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Case Scenario 7:

A 50-year-old male with a history of chronic alcohol consumption was hospitalized with clinical features including anxiety, confusion, memory loss, and impaired coordination. Laboratory evaluation revealed reduced serum thiamine levels and low RBC transketolase activity.

1. What is the most probable diagnosis?
2. Name the biochemical investigations useful in confirming this diagnosis
3. Describe the dietary sources, recommended dietary allowance (RDA), and biochemical functions of the deficient vitamin.

Answer:

a) Probable Diagnosis:
The most likely diagnosis is Wernicke’s Encephalopathy, a neurological condition caused by a deficiency of thiamine (vitamin B1).

b) Biochemical Investigations for Diagnosis:

1. 1. Serum Thiamine Level – Often decreased in deficiency states.
   2. Erythrocyte Transketolase Activity – A functional test; reduced activity indicates thiamine deficiency.

c)Dietary Sources:

1. 1. Whole grains (brown rice, oats, wheat germ)
   2. Legumes
   3. Nuts and seeds
   4. Pork
   5. Fortified cereals and breads

• • Recommended Dietary Allowance (RDA):

1. 1. Adult males: 1.2 mg/day
   2. Adult females: 1.1 mg/day
   3. Increased requirements during pregnancy, lactation, and in alcoholics.

• • Biochemical Functions:
    Thiamine is converted to its active form, thiamine pyrophosphate (TPP), which serves as a coenzyme in several key metabolic reactions:

1. 1. 1. Carbohydrate metabolism:
         • Pyruvate dehydrogenase (links glycolysis to TCA cycle)
         • α-Ketoglutarate dehydrogenase (TCA cycle)
         • Branched-chain α-keto acid dehydrogenase
      2. Pentose Phosphate Pathway:
         • Transketolase (important for nucleotide synthesis and reducing equivalents in the form of NADPH)
      3. Nervous System Function:
         • Thiamine plays a vital role in nerve impulse conduction and neurotransmitter synthesis.

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Case Scenario 8:

A 35-year-old male from a low-income background presents to the outpatient department with complaints of progressive weakness in his legs, tingling and numbness in the feet, and difficulty walking without support. He has a history of consuming only polished white rice as his staple food and reports chronic alcohol consumption. On clinical examination, there is muscle wasting and loss of reflexes in the lower limbs, but no evidence of edema.

1. What is the most probable diagnosis?
2. Explain the underlying biochemical basis and clinical features of this condition.
3. What is the significance of low RBC transketolase activity?

Answer:

a) Probable Diagnosis:
The most likely diagnosis is Dry Beriberi, which results from thiamine (vitamin B1) deficiency affecting the nervous system.

b) Biochemical Basis and Clinical Features:

• • Biochemical Basis:
    • Thiamine is required for energy metabolism as it acts as a coenzyme (in the form of Thiamine Pyrophosphate, TPP) in:
      • Pyruvate dehydrogenase (linking glycolysis to the TCA cycle)
      • α-Ketoglutarate dehydrogenase (TCA cycle)
      • Transketolase (Pentose phosphate pathway)
    • Deficiency impairs ATP production, especially affecting neurons due to their high energy demand.
  • Clinical Features of Dry Beriberi:
    • Symmetrical peripheral neuropathy (tingling, numbness)
    • Muscle weakness and wasting, especially in lower limbs
    • Difficulty in walking, foot drop
    • Hyporeflexia or areflexia
    • No edema (differentiates it from wet beriberi)

c)

• • Low RBC transketolase activity indicates reduced thiamine-dependent enzyme activity, confirming thiamine deficiency.
  • Transketolase (HMP pathway) uses TPP as a cofactor

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Case Scenario 9:

A 30-year-old man who follows a strict vegan diet (excluding even dairy products) presents with complaints of generalized weakness, pallor, loss of sensation in the limbs, and mental confusion. Laboratory findings show hemoglobin level of 7 g/dL and peripheral blood smear reveals large, immature, and abnormal red blood cells. Urine examination detects increased levels of methylmalonic acid.

1. Identify the deficient vitamin.
2. Mention its functions, absorption, daily requirement, and manifestations of its deficiency.

Answer:

a) Deficient Vitamin: The deficient vitamin is Vitamin B₁₂ (Cobalamin).

b) Functions of Vitamin B₁₂:

1. 1. Coenzyme functions:
      • Methylcobalamin: Coenzyme for methionine synthase, which converts homocysteine to methionine (involved in DNA synthesis and methylation).
      • Adenosylcobalamin: Coenzyme for methylmalonyl-CoA mutase, which converts methylmalonyl-CoA to succinyl-CoA in fatty acid metabolism.
   2. Essential for:
      • DNA synthesis (especially in rapidly dividing cells like RBC precursors)
      • Myelin sheath maintenance in the nervous system

Absorption: Requires intrinsic factor (secreted by gastric parietal cells) for absorption in the terminal ileum

Daily Requirement (RDA): Adults: 2.4 μg/day

Deficiency Manifestations:

1. 1. Hematological:
      • Megaloblastic anemia (large, immature RBCs)
      • Fatigue, pallor, weakness
   2. Neurological:
      • Peripheral neuropathy (tingling, numbness)
      • Loss of proprioception and vibration sense
      • Mental confusion and cognitive decline
   3. Biochemical:
      • Elevated methylmalonic acid and homocysteine in serum/urine

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Case Scenario 10:

A 39-year-old male presents with complaints of oral mucosal ulcers and extreme fatigue for the past two weeks. He has a history of receiving methotrexate treatment for testicular cancer. Investigations reveal decreased hemoglobin levels, low serum folate, and a peripheral blood smear showing megaloblastic cells.

a) What is the most probable diagnosis?
b) Mention the dietary sources, RDA, and biochemical functions of the deficient vitamin.
c) Explain the role of methotrexate in contributing to this condition.

Answer:

a) Probable Diagnosis: Folate deficiency–induced megaloblastic anemia

b) Dietary Sources, RDA, and Biochemical Functions of Folate (Vitamin B₉):

• • Dietary Sources:
    • Green leafy vegetables (spinach, lettuce)
    • Legumes (lentils, beans)
    • Citrus fruits
    • Whole grains
    • Liver and fortified cereals
  • Recommended Dietary Allowance (RDA):
    • Adult men: 400 µg/day
    • Pregnant women: 600 µg/day
  • Biochemical Functions:
    • Folate is converted to tetrahydrofolate (THF), which acts as a coenzyme in:
      • One-carbon metabolism (important for DNA and RNA synthesis)
      • Purine and thymidylate synthesis
      • Conversion of homocysteine to methionine (via interaction with vitamin B₁₂)
    • Essential for cell division, especially in rapidly dividing cells like bone marrow precursors

c) Role of Methotrexate in Folate Deficiency:

• • Methotrexate is a folate antagonist.
  • It inhibits dihydrofolate reductase (DHFR), the enzyme that converts dihydrofolate (DHF) to tetrahydrofolate (THF).
  • This inhibition blocks folate metabolism, impairing DNA synthesis, and leads to megaloblastic anemia and symptoms like oral ulcers and fatigue.

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Case Scenario 11:

A newborn baby, still in the hospital, presents with signs of subcutaneous hemorrhage, pale (whitish) stools, and steatorrhea. Laboratory investigations reveal low prothrombin levels and prolonged clotting time.

a) Identify the deficient vitamin.
b) Mention its various forms.
c) Describe its physiological functions and dietary sources.

Answer:

a) Deficient Vitamin: The deficient vitamin is Vitamin K.

b) Forms of Vitamin K:

• • Vitamin K₁ (Phylloquinone): Found in plant sources
  • Vitamin K₂ (Menaquinone): Synthesized by intestinal bacteria
  • Vitamin K₃ (Menadione): A synthetic, water-soluble form (not used routinely due to toxicity concerns in neonates)

c) Physiological Functions of Vitamin K:

• • Acts as a coenzyme for γ-glutamyl carboxylase, which activates clotting factors by enabling γ-carboxylation of glutamate residues
  • Essential for activation of clotting factors II (prothrombin), VII, IX, X and proteins C and S (natural anticoagulants)
  • Plays a role in bone metabolism by helping in the activation of osteocalcin

Dietary Sources of Vitamin K:

• • • Vitamin K₁:
      • Green leafy vegetables (spinach, kale, broccoli)
      • Cabbage, lettuce, and plant oils
    • Vitamin K₂:
      • Synthesized by gut microbiota
      • Also found in fermented foods (e.g. natto)

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Case Scenario 12:

A 45-year-old male agricultural worker from a low-income rural area presents with complaints of persistent diarrhea, dark, scaly skin lesions on sun-exposed areas, and irritability and confusion. On dietary assessment, it is noted that his diet mainly consists of maize (corn) and lacks adequate protein.

a) What is the most probable diagnosis?
b) Mention the vitamin deficiency responsible, its biochemical functions, and daily requirements.
c) Describe the classical clinical features and dietary sources of the deficient vitamin.

Answer:

a) Probable Diagnosis: The patient is most likely suffering from Pellagra

b) Deficient Vitamin – Niacin (Vitamin B₃):

• • Biochemical Functions:
  • Niacin is the precursor of coenzymes NAD⁺ (nicotinamide adenine dinucleotide) and NADP⁺, which are essential for:
  • Redox reactions in glycolysis, TCA cycle, and oxidative phosphorylation
  • Fatty acid and cholesterol synthesis
  • DNA repair and cell signaling
  • Daily Requirement (RDA):
  • Men: 16 mg/day
  • Women: 14 mg/day

c) Clinical Features and Dietary Sources:

Classical Clinical Features – The 3 Ds of Pellagra:

1. 1. 1. Dermatitis – Symmetrical, pigmented, scaly rash on sun-exposed areas (Casal’s necklace around neck)
      2. Diarrhea – Due to mucosal atrophy in the GI tract
      3. Dementia – Neurological symptoms like confusion, irritability, memory loss

(If untreated, a 4th D: Death can occur)

• • Dietary Sources:

• • • Meat (especially liver)
    • Fish
    • Whole grains
    • Legumes
    • Peanuts
    • Fortified cereals

• • Risk Factors:

• • • Diets high in maize (corn) that is not nixtamalized (alkali-treated)
    • Chronic alcoholism
    • Hartnup disease or carcinoid syndrome (tryptophan diversion or malabsorption

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Case Scenario 13:

A 22-year-old college student from a hostel reports to the outpatient department with complaints of sore throat, cracks and fissures at the corners of the mouth, burning sensation in the eyes, and a purplish-red tongue. Clinical examination reveals angular stomatitis, cheilitis, glossitis, and seborrheic dermatitis around the nose and ears. His diet mainly consists of polished rice and lacks milk and green vegetables.

a) What is the most probable diagnosis?
b) Mention the functions, daily requirement, and coenzyme forms of the deficient vitamin.
c) List the clinical manifestations and dietary sources of this vitamin.

Answer:

a) Probable Diagnosis: The most likely diagnosis is Vitamin B₂ (Riboflavin) deficiency.

b) Functions, RDA, and Coenzyme Forms:

• • Functions:
    • Riboflavin is the precursor of two major coenzymes:
      • FMN (Flavin Mononucleotide)
      • FAD (Flavin Adenine Dinucleotide)
    • These coenzymes participate in oxidation-reduction reactions in:
      • Electron transport chain
      • TCA cycle (succinate dehydrogenase)
      • Fatty acid oxidation
    • Important for energy metabolism and maintenance of mucous membranes and skin
  • Recommended Dietary Allowance (RDA):
    • Adult men: 1.3 mg/day
    • Adult women: 1.1 mg/day

c) Clinical Manifestations and Dietary Sources:

• • Clinical Manifestations of Riboflavin Deficiency:
    • Angular stomatitis – cracks at the corners of the mouth
    • Cheilitis – inflammation of the lips
    • Glossitis – magenta-colored tongue
    • Seborrheic dermatitis – especially around nose, ears, and eyelids
    • Photophobia and burning eyes
    • Normocytic anemia
  • Dietary Sources of Riboflavin:
    • Milk and dairy products (best sources)
    • Eggs
    • Green leafy vegetables
    • Whole grains
    • Meat, liver

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Case Scenario 14:

A 28-year-old female presents with complaints of irritability, peripheral neuropathy (tingling and numbness in her hands and feet), and seborrheic dermatitis around her face and neck. She has a history of prolonged treatment with isoniazid for tuberculosis. Laboratory tests reveal microcytic hypochromic anemia.

a) What is the most probable diagnosis?
b) Describe the biochemical functions, daily requirements, and absorption of the deficient vitamin.
c) Outline the clinical manifestations and dietary sources of this vitamin. Also, mention how isoniazid contributes to this deficiency.

Answer:

a) Probable Diagnosis: Vitamin B6 (Pyridoxine) deficiency.

b) Biochemical Functions, Daily Requirements, and Absorption:

• • Biochemical Functions:
    • Vitamin B6 is converted into pyridoxal phosphate (PLP), an active coenzyme.
    • PLP acts as a coenzyme in:
      • Amino acid metabolism (transamination, decarboxylation)
      • Neurotransmitter synthesis (serotonin, dopamine, GABA)
      • Heme synthesis (important for hemoglobin production)
      • Glycogen phosphorylase activity
  • Daily Requirement (RDA):
    • Adults: 1.3–1.7 mg/day

c) Clinical Manifestations, Dietary Sources, and Role of Isoniazid:

• • Clinical Manifestations:
    • Peripheral neuropathy (tingling, numbness, burning sensation)
    • Seborrheic dermatitis (especially around face and neck)
    • Irritability, depression, confusion
    • Microcytic hypochromic anemia due to impaired heme synthesis
    • Glossitis and cheilitis may also occur
  • Dietary Sources:
    • Poultry, fish, and meat
    • Whole grains and fortified cereals
    • Bananas, potatoes, and nuts
  • Role of Isoniazid:
    • Isoniazid forms complexes with pyridoxal phosphate, inactivating vitamin B6, leading to functional deficiency.
    • Hence, pyridoxine supplementation is often given with isoniazid therapy to prevent neuropathy.