A 7-day-old male infant presents to the pediatrician for weight loss. There is no history of excessive crying, irritability, lethargy, or feeding difficulty. The parents deny any history of fast breathing, bluish discoloration of lips/nails, fever, vomiting, diarrhea, or seizures. He was born at full term by vaginal delivery without any perinatal complications and his birth weight was 3.6 kg (8 lb). Since birth he has been exclusively breastfed and passes urine six to eight times a day. His physical examination, including vital signs, is completely normal. His weight is 3.3 kg (7.3 lb); length and head circumference are normal for his age and sex. Which of the following is the next best step in the management of the infant?

Evaluation of the mother for malnutrition

Admission of the infant in the NICU to treat with empiric intravenous antibiotics

Emphasize the need to clothe the infant warmly to prevent hypothermia

Supplementation of breastfeeding with an appropriate infant formula

A two-year-old female presents to the pediatrician with her mother for a routine well-child visit. Her mother is concerned that the patient is a picky eater and refuses to eat vegetables. She drinks milk with meals and has juice sparingly. She goes to sleep easily at night and usually sleeps for 11-12 hours. The patient has trouble falling asleep for naps but does nap for 1-2 hours a few times per week. She is doing well in daycare and enjoys parallel play with the other children. Her mother reports that she can walk down stairs with both feet on each step. She has a vocabulary of 10-25 words that she uses in the form of one-word commands. She is in the 42nd percentile for height and 48th percentile for weight, which is consistent with her growth curves. On physical exam, she appears well nourished. She can copy a line and throw a ball. She can follow the command to “give me the ball and then close the door.” This child is meeting her developmental milestones in all but which of the following categories?

Social and receptive language skills

This child is developmentally normal

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 4-year-old girl is brought to the physician by her parents because she is severely underweight. She is easily fatigued and has difficulty keeping up with other children at her daycare. She has a good appetite and eats 3 full meals a day. She has 4 to 5 bowel movements daily with bulky, foul-smelling stools that float. She has had recurrent episodes of sinusitis since infancy. Her parents report that she recently started to snore during her sleep. She is at the 15th percentile for height and 3rd percentile for weight. Her vital signs are within normal limits. Examination shows pale conjunctivae. A few scattered expiratory crackles are heard in the thorax. There is abdominal distention. Which of the following is the most likely underlying cause of this patient's failure to thrive?

Exocrine pancreatic insufficiency

T. whippelii infiltration of intestinal villi

Impaired intestinal amino acid transport

Small intestine bacterial overgrowth

Intestinal inflammatory reaction to gluten

A 4-day-old male newborn is brought to the physician for a well-child examination. His mother is concerned that he is losing weight. He was born at 40 weeks' gestation and weighed 2980g (6-lb 9-oz); he currently weighs 2830g (6-lb 4-oz). Pregnancy was uncomplicated. He passed stool and urine 8 and 10 hours after delivery. He has been exclusively breast fed since birth and feeds 11–12 times daily. His mother says she changes 5–6 heavy diapers daily. Examination shows an open and firm anterior fontanelle. Mucous membranes are moist. Capillary refill time is less than 2 seconds. Cardiopulmonary examination shows no abnormalities. Which of the following is the most appropriate next best step in management?

Serum creatinine and urea nitrogen

A 6-month-old girl is brought to the physician because of drooling and excessive crying for 3 days. She calms down when cuddled or with a pacifier in her mouth. She feeds well and has no vomiting or diarrhea. She was breastfed exclusively for 5 months. She is given no medications and was born at 39 weeks gestation via spontaneous vaginal delivery. She is up to date on all vaccines and is meeting all developmental milestones. At the clinic, her weight is 7.3 kg (16 lb 1 oz) and her height is 65.8 cm (25.9 in) in length. She appears irritable. Her pulse is 124/min, the respirations are 32/min, the blood pressure is 92/63 mm Hg, and the temperature is 36.8°C (98.2°F). On physical examination, she has no conjunctivitis, cervical lymphadenopathy, or pharyngeal erythema. Which element of the physical examination is most likely to be present in this patient?

Eruption of mandibular incisors

Crying on frontal sinus palpation

Closure of the anterior fontanel

Erythema and fluctuance of the submandibular area

Failure to thrive evaluation for USMLE Step 2 CK: High-Yield Pediatrics Lessons

FTT Definition - Sizing Up The Problem

Definition: FTT is inadequate weight gain. Key indicators:
- Weight-for-age < 3rd or 5th percentile.
- Weight-for-length/height < 3rd or 5th percentile.
- Weight drop crossing two major centile lines (e.g., 90th → 50th).
Growth Charts:
- Use WHO charts for children < 2 years.
- Use IAP (Indian Academy of Pediatrics) charts for > 2 years.

⭐ Most FTT is non-organic, often due to inadequate caloric intake or psychosocial factors, rather than an underlying medical condition.

Weight-for-age growth chart showing faltering growth

FTT Etiology - The 'Why' Behind It

Primary Division: FTT is broadly classified into Organic (underlying medical condition) and Non-Organic (psychosocial) causes, often with significant overlap.

Weight-for-age growth chart showing failure to thrive

⭐ The most common cause of FTT is non-organic/psychosocial, accounting for over 75% of cases. It's often a diagnosis of exclusion after ruling out organic pathology.

Evaluation Pathway - The FTT Workup

Initial Steps: Thorough history (including 72-hr diet recall), observed feeding, and meticulous growth chart plotting are paramount.
Screening Labs (Tier 1): If no cause is evident after initial assessment and dietary counseling:
- Complete Blood Count (CBC)
- Urinalysis & culture
- Basic Metabolic Panel (BMP)
- Stool for occult blood, pH, reducing substances

Weight-for-age growth chart showing improved growth

⭐ In >85% of cases, a cause for FTT is found through a detailed history and physical exam alone, making extensive, unfocused lab testing low-yield.

Management Strategy - The Recovery Plan

Nutritional Rehabilitation: The cornerstone of management.
- Goal: Achieve catch-up growth with high-calorie diet (1.5-2x RDA).
- Caloric Requirement Calculation:
  - $Required,Kcal/kg = \frac{Ideal,weight,for,height \times 120}{Actual,weight}$
- Use high-density feeds (e.g., 1 kcal/mL).
Multidisciplinary Team: Involve pediatrician, dietitian, social worker, and psychologist for comprehensive care.
Monitoring:
- Initial daily weight checks.
- Weekly length and head circumference measurements.

⭐ High-Yield: Expect a weight gain of >20-30 g/day in a hospitalized child during initial recovery.

Weight and Height Catch-up Growth in Infants

High‑Yield Points - ⚡ Biggest Takeaways

Most common cause of FTT is non-organic (e.g., psychosocial deprivation).

Weight is the first parameter to fall, followed by height, and lastly head circumference.

Wasting (↓ weight-for-height) indicates acute malnutrition; Stunting (↓ height-for-age) suggests chronic malnutrition.

A detailed dietary history and observation of feeding are the most crucial diagnostic tools.

Hospitalization showing catch-up growth strongly suggests a non-organic cause.

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