A 61-year-old woman presents for a routine health visit. She complains of generalized fatigue and lethargy on most days of the week for the past 4 months. She has no significant past medical history and is not taking any medications. She denies any history of smoking or recreational drug use but states that she drinks "socially" approx. 6 nights a week. She says she also enjoys a "nightcap," which is 1–2 glasses of wine before bed every night. The patient is afebrile, and her vital signs are within normal limits. On physical examination, there is significant pallor of the mucous membranes. Laboratory findings are significant for a mean corpuscular volume (MCV) of 72 fL, leukocyte count of 4,800/mL, hemoglobin of 11.0 g/dL, and platelet count of 611,000/mL. Stool guaiac test is negative. She is started on oral ferrous sulfate supplements. On follow-up, her laboratory parameters show no interval change in her MCV or platelet level, and she reports good compliance with the medication. Which of the following is the best next step in the management of this patient?

Transfuse the patient with whole blood

Continue oral ferrous sulfate and supplement with omeprazole

Continue oral ferrous sulfate and supplement with ascorbic acid

A 67-year-old male presents to his primary care physician complaining of left hip pain for the past six months. He denies any trauma or recent falls. He is accompanied by his wife who reports that he has experienced progressive hearing loss over the same time period. The patient has also noticed that he is no longer able to fit into his favorite hat even though it previously fit well. A radiograph of the patient’s pelvis is shown. Which of the following laboratory abnormalities is most likely to be found in this patient?

Elevated serum alkaline phosphatase

Decreased serum alkaline phosphatase

Elevated serum parathyroid hormone

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

A 67-year-old male presents with left hip pain. Examination reveals mild effusions in both knees, with crepitus in both patellofemoral joints. He states his hearing has worsened recently and that he feels like his hats don't fit anymore. Bone scan reveals diffuse uptake in the calvarium, right proximal femur, and left ilium. Which of the following laboratory abnormalities would be expected in this patient?

Increased serum alkaline phosphatase

Decreased serum alkaline phosphatase

Increased serum parathyroid hormone

Decreased serum parathyroid hormone

A 5-month-old male presents to the pediatrician with his mother for a well visit. The patient was born at 35 weeks gestation to a 30-year-old gravida 2 via vaginal delivery. The pregnancy and labor were uncomplicated. The patient required no resuscitation after delivery and was discharged from the hospital on day two of life. His mother now reports that the patient has been exclusively breastfed since birth, and she says that feedings have been going well, and that the patient appears satisfied afterwards. The patient feeds for 30 minutes every two hours and urinates 8-10 times per day. The patient’s mother reports that she eats a varied diet that includes animal products, but she worries that the patient is not meeting his nutritional needs with breastmilk alone. The patient’s height and weight at birth were in the 15th and 20th percentile, respectively. His height and weight are now in the 20th and 25th percentile, respectively. His temperature is 98.1°F (36.7°C), blood pressure is 58/46 mmHg, pulse is 128/min, and respirations are 34/min. On physical exam, the patient appears well-developed and well-nourished. He has mild conjunctival pallor. Which of the following is the most appropriate guidance regarding this patient’s nutritional needs?

Supplement his diet with iron and vitamin D

Supplement his diet with formula

No changes are necessary to his diet

Micronutrient deficiencies for USMLE Step 2 CK: High-Yield Pediatrics Lessons

Iron Deficiency - The Pale Story

Etiology: Most common nutritional anemia worldwide.
- Causes: Inadequate intake, prematurity, exclusive breastfeeding >6mo, malabsorption (celiac disease), chronic blood loss (hookworm).
Clinical Features:
- Pallor, fatigue, irritability.
- Pica (pagophagia: ice), koilonychia (spoon nails), glossitis.
- Plummer-Vinson syndrome: triad of dysphagia, esophageal webs, and IDA.
Labs & Diagnosis:
- Microcytic hypochromic anemia (↓ MCV, ↓ MCH).
- ↓ Serum Ferritin (<15 ng/mL), ↓ Serum Iron, ↑ TIBC.
Treatment: Oral elemental iron (3-6 mg/kg/day).

⭐ High-Yield: The earliest biochemical marker to decrease in iron deficiency is serum ferritin, reflecting depleted iron stores before anemia is apparent.

Vitamin A - See The Light

Function: Essential for vision (retinal pigment), immune function, and epithelial cell integrity.
Ocular Manifestations (Xerophthalmia):
- XN: Night blindness (earliest symptom).
- X1A/B: Conjunctival xerosis & Bitot’s spots.
- X2/X3: Corneal xerosis, ulceration & keratomalacia.
- XS/XF: Corneal scarring & xerophthalmic fundus.
Systemic: Follicular hyperkeratosis (phrynoderma), impaired immunity.
Diagnosis: Serum retinol < 20 µg/dL.
Treatment (WHO Schedule): Oral Vitamin A on days 0, 1, and 14.
- <6 mo: 50,000 IU
- 6-12 mo: 100,000 IU
- 1 yr: 200,000 IU

⭐ Bitot's Spots (X1B): Pathognomonic. Triangular, pearly-white/yellowish, foamy plaques of keratinized epithelium, classically on the temporal bulbar conjunctiva.

Bitot's spots on conjunctiva due to Vitamin A deficiency

Vitamin D & Calcium - Rickets Rules

Biochemistry: ↓ Ca²⁺, ↓ PO₄³⁻, ↑ Alkaline Phosphatase (ALP), ↑ PTH.
- ALP is the earliest marker to ↑.
Clinical Features:
- Early: Craniotabes, wrist widening.
- Late: Rachitic rosary, Harrison's sulcus, delayed fontanelle closure, genu varum/valgum.
X-Ray Findings (Metaphysis): Cupping, fraying, splaying.
- Looser's zones (pseudofractures) in osteomalacia.

X-ray findings of rickets in wrist and knee

Treatment (Nutritional Rickets):
- Stoss Therapy: 600,000 IU Vitamin D₃ single dose.
- Daily: 3000-5000 IU for 6 weeks, then 400 IU prophylaxis.
- Always supplement with Calcium.

⭐ First radiological sign of healing is the appearance of the line of provisional calcification (usually within 2-4 weeks).

VDDR-II: Features rickets + alopecia + very high 1,25(OH)₂D levels due to receptor defect.

Iodine & Zinc - The Essential Trace

Iodine Deficiency Disorders (IDD)
- Manifestations: Goiter, hypothyroidism, and cretinism (neurologic/myxedematous).
- Pathophysiology: ↓ Thyroid hormone synthesis → ↑ TSH.
- Diagnosis: Median urinary iodine < 100 µg/L.
- Prevention: Iodized salt (>15 ppm at consumer level).
Zinc Deficiency
- Classic Triad: Acrodermatitis enteropathica (periorificial/acral rash), alopecia, diarrhea.
- Other signs: Growth retardation, immune dysfunction.
⭐ High-Yield: Zinc supplementation (10-20 mg/day for 10-14 days) is crucial in acute diarrhea, reducing duration and severity.

High‑Yield Points - ⚡ Biggest Takeaways

Vitamin A deficiency presents with Bitot's spots and keratomalacia; the first dose is given at 9 months with the measles vaccine.

Rickets (Vitamin D deficiency) shows cupping, fraying, and splaying of metaphysis on X-ray, with rachitic rosary clinically.

Scurvy (Vitamin C deficiency) is marked by bleeding gums, corkscrew hair, and subperiosteal hemorrhages.

Iron deficiency, the most common nutritional disorder, causes microcytic hypochromic anemia; serum ferritin is the best screening test.

Iodine deficiency is the most common preventable cause of intellectual disability (cretinism).

Zinc deficiency classically presents as acrodermatitis enteropathica with periorificial dermatitis.

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