A 27-year-old female presents to general medical clinic for a routine checkup. She has a genetic disease marked by a mutation in a chloride transporter. She has a history of chronic bronchitis. She has a brother with a similar history of infections as well as infertility. Which of the following is most likely true regarding a potential vitamin deficiency complication secondary to this patient's chronic illness?

It may manifest itself as a prolonged PT

It may result in connective tissue defects

It may result in corneal vascularization

It may result in the triad of confusion, ophthalmoplegia, and ataxia

It may be exacerbated by excessive ingestion of raw eggs

A 7-year-old girl presents to her primary care physician for a routine check-up. The physician allows the medical student to perform a physical examination. The medical student notes hearing impairment as well as the findings show in Figures A and B. Radiographs show indications of multiple old fractures of the humerus that have healed. After questioning the girl’s parents, the medical student learns that in addition, the patient is extremely picky with her food and eats a diet consisting mainly of cereal and pasta. What is the most likely etiology of the patient’s disease?

Dietary deficiency of ascorbic acid

Defective mineralization of cartilage

A 21-year-old woman is admitted to the hospital for severe malnutrition with a BMI of 15 kg/m2. Past medical history is significant for chronic anorexia nervosa. During the course of her stay, she is treated with parenteral fluids and nutrition management. On the 4th day, her status changes. Her blood pressure is 110/75 mm Hg, heart rate is 120/min, respiratory rate is 25/min, and temperature is 37.0°C (98.6°F). On physical exam, her heart is tachycardic with a regular rhythm and her lungs are clear to auscultation bilaterally. She appears confused, disoriented, and agitated. Strength in her lower extremities is 4/5. What is the next step in management?

Arrange for outpatient counseling

Doppler ultrasound on lower extremities

A 17-year-old girl is brought in by her mother due to rapid weight loss over the past month. The patient says she has been having episodes of diarrhea, which she attributes to laxatives she takes regularly to keep her weight down. She also says she has not had her period yet. The patient’s mother adds that the patient has been underperforming at school and acting very strangely at home. Her current BMI is 16.8 kg/m2. On physical examination, the skin on her limbs and around her neck is inflamed and erythematous. Her tongue is bright red and smooth. She states that over the last 2 weeks, she has been eating nothing but small portions of fruit. She is diagnosed with a vitamin deficiency. Which of the following statements is true about the vitamin most likely deficient in this patient?

Synthesis requires vitamin B2 and B6

It increases the GI absorption of iron

Synthesis requires vitamin B1 and B6

It is used to treat hypertension

Nutritional diseases for USMLE Step 2 CK: High-Yield Pathology Lessons

Protein-Energy Malnutrition - Empty Plate Problems

A spectrum of diseases from inadequate protein and calorie intake, primarily affecting somatic (skeletal muscle) and visceral (organ) protein compartments.
Marasmus (Total Calorie Deficiency)
- Adaptation to starvation; "to waste away."
- Clinical: Severe muscle wasting (emaciation), loss of subcutaneous fat, prominent bones, "old man" face.
- Labs: Serum albumin is near-normal.
- Somatic protein compartment depleted.
Kwashiorkor (Protein Deficiency > Calorie Deficiency)
- Maladaptive response; "sickness of the weaned child."
- Clinical: Pitting edema, ascites, hepatomegaly (fatty liver), "flaky-paint" dermatosis, alternating hair color (flag sign).
- Labs: Markedly ↓ serum albumin.
- Visceral protein compartment depleted.

⭐ High-Yield: The fatty liver in Kwashiorkor is due to decreased apolipoprotein synthesis, which impairs the export of VLDL from the liver.

Fat-Soluble Vitamins - ADEK's Fat Stash

Absorbed with lipids; deficiencies seen in malabsorption (celiac, cystic fibrosis) and with mineral oil intake. 📌 All Dogs Eat Kibble.

Vitamin	Core Function(s)	Deficiency Manifestations	Excess Manifestations
A (Retinol)	Vision, antioxidant, epithelial cell differentiation	Night blindness, xerophthalmia, Bitot spots	Teratogenic, hepatotoxicity, alopecia
D (Calciferol)	↑ Ca²⁺ & PO₄³⁻ absorption	Rickets (kids), osteomalacia (adults)	Hypercalcemia, confusion
E (Tocopherol)	Antioxidant (protects RBCs)	Hemolytic anemia, spinocerebellar tract demyelination	↑ Warfarin effect, bleeding
K (Phytonadione)	Coagulation factors (II, VII, IX, X, C, S)	Hemorrhage, ↑ PT/PTT	Hemolytic anemia (high doses)

Vitamin A absorption, metabolism, and transport

Water-Soluble Vitamins - B & C's Washout

General: Absorbed in the small intestine; excess excreted in urine. Not stored in the body (except B12, B9), requiring consistent dietary intake. Act as crucial coenzymes in metabolic pathways.
Vitamin C (Ascorbic Acid)
- Function: Antioxidant; essential for collagen synthesis (hydroxylation of proline/lysine).
- Deficiency (Scurvy): Impaired wound healing, bleeding gums, perifollicular hemorrhage.
B-Complex Vitamins
- Function: Coenzymes in energy metabolism (e.g., Thiamine in PDH complex).
- 📌 Mnemonic: B vitamins are coenzymes for "Burning" fuel.

⭐ Thiamine (B1) Deficiency: In alcoholics, can lead to Wernicke-Korsakoff syndrome. Always give thiamine before glucose to prevent precipitating encephalopathy.

Essential Minerals - Tiny But Mighty

Iron (Fe): O₂ transport (Hb, myoglobin); cytochrome function.
- Deficiency: Microcytic, hypochromic anemia; koilonychia.
- Excess: Hemochromatosis (organ damage from iron deposition).
Iodine (I): Synthesis of thyroid hormones ($T_3, T_4$).
- Deficiency: Goiter, hypothyroidism, cretinism.
Copper (Cu): Cofactor for lysyl oxidase, tyrosinase, cytochrome c oxidase.
- Deficiency (Menkes): Brittle, "kinky" hair, growth retardation.
- Excess (Wilson's): Kayser-Fleischer rings, liver disease.
Zinc (Zn): Cofactor for >100 enzymes (e.g., carbonic anhydrase).
- Deficiency: Delayed wound healing, hypogonadism, dysgeusia.

⭐ Acrodermatitis enteropathica, a rash around body orifices, is a classic sign of severe Zinc deficiency, often tested alongside delayed wound healing and anosmia/dysgeusia.

High‑Yield Points - ⚡ Biggest Takeaways

Marasmus results from total calorie malnutrition, leading to severe muscle wasting and loss of subcutaneous fat.

Kwashiorkor is primarily a protein deficiency, characterized by pitting edema, fatty liver, and skin lesions.

Vitamin A deficiency classically presents with night blindness (nyctalopia) and Bitot's spots on the conjunctiva.

Vitamin C deficiency impairs collagen synthesis, causing scurvy (bleeding gums, poor wound healing).

Vitamin D deficiency leads to Rickets in children and Osteomalacia in adults.

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