What is the diagnosis for a 10-month-old infant with irritability during feeding and multiple vomiting, weighing less than the 3rd percentile, with height and head circumference at the 25th percentile, and having two healthy older brothers?

Organic Failure to Thrive

This 10-month-old infant has organic failure to thrive (Option C), as evidenced by the combination of specific gastrointestinal symptoms (irritability during feeding and multiple vomiting episodes) with disproportionate growth failure affecting weight only. 1

Key Diagnostic Features Supporting Organic Etiology

The growth pattern is pathognomonic for organic failure to thrive: weight below the 3rd percentile while height and head circumference remain at the 25th percentile indicates acute malnutrition affecting weight first, which is the critical distinguishing feature of organic rather than nonorganic failure to thrive. 1 This disproportionate growth failure, with only weight being affected rather than global growth delay, strongly points to an organic cause. 1

The presence of specific gastrointestinal symptoms is decisive:

• Irritability during feeding combined with multiple vomiting episodes points to specific organic pathology such as gastroesophageal reflux disease (GERD), feeding/swallowing dysfunction, or other gastrointestinal pathology. 1
• These are not simply decreased intake without symptoms, which would be more consistent with nonorganic failure to thrive. 1

Why Other Options Are Incorrect

Normal development (Option A) is excluded because weight below the 3rd percentile represents significant growth failure requiring intervention. 1

Nonorganic failure to thrive (Option B) is unlikely for several critical reasons:

• The absence of psychosocial deprivation and the presence of specific GI symptoms (vomiting and feeding irritability) rather than simple decreased intake suggest an organic etiology. 1
• Nonorganic failure to thrive typically presents with food refusal, food fixation, abnormal parental feeding practices, onset after a specific trigger, and anticipatory gagging—none of which are described in this case. 2
• The presence of two healthy older brothers makes environmental or psychosocial factors less likely. 1

Chromosomal abnormalities (Option D) are unlikely because normal birth history with two healthy siblings makes chromosomal abnormalities improbable. 1 Additionally, chromosomal abnormalities typically present with proportionate growth failure affecting weight, height, and head circumference equally, not the isolated weight faltering seen here. 1

Immediate Clinical Approach Required

Gastroenterology referral is mandatory for evaluation of GERD, swallowing dysfunction, or other GI pathology given the vomiting and feeding irritability. 1

Initial diagnostic workup should include:

• Video swallow study to assess for swallowing dysfunction and aspiration risk 1
• Extended 24-hour esophageal pH monitoring, barium swallow, and gastric scintiscan to evaluate for GERD 1
• Complete blood count, comprehensive metabolic panel, and thyroid function tests to exclude systemic disease 1
• Sweat chloride test for cystic fibrosis screening (sensitivity 90%, specificity 99%) 1

Critical pitfall to avoid: Do not delay gastroenterology evaluation while pursuing extensive laboratory testing, as the clinical presentation clearly indicates a gastrointestinal organic cause requiring specialized assessment. 1