Is Failure to Thrive a Diagnosis?
Failure to thrive (FTT) is not a final diagnosis—it is a clinical descriptor of inadequate growth that requires investigation to identify the underlying cause. FTT represents a symptom or presentation rather than a disease entity itself, and should prompt a systematic search for the actual etiology 1, 2, 3.
Understanding FTT as a Clinical Presentation
- FTT is defined as growth retardation without a known cause in infants and young children, making it a clinical presentation rather than a definitive diagnosis 2
- The preferred updated terminology is "growth faltering," which more accurately reflects that this is a descriptive finding rather than a diagnosis 2
- FTT should be conceptualized as a sign that triggers diagnostic evaluation, similar to how fever or anemia prompts investigation for underlying causes 1, 3
Why FTT Requires Further Diagnosis
- The American College of Medical Genetics explicitly lists "failure to thrive" as a reason to consider genetic consultation to rule out chromosomal, metabolic, or syndromic diagnoses—not as a final diagnosis itself 4
- Inadequate caloric intake is the most common underlying cause (61.4% of cases), followed by psychiatric/behavioral disorders (17.2%), endocrinologic disorders (9%), recurrent infections (6.4%), gastrointestinal diseases (1.9%), and cardiac disorders 5
- Only 1.3% of extensive diagnostic workup leads to identifying specific organic causes, but this does not negate the need to identify the actual etiology 5
The Diagnostic Approach
When FTT is identified, the following systematic evaluation is required:
Initial Assessment
- Document growth trajectory using standardized WHO growth charts for weight, height, and head circumference to confirm the growth faltering pattern 1
- Obtain detailed feeding history including difficulties with feeding, swallowing issues, vomiting, or gastroesophageal reflux 1
- Evaluate for physical signs including muscle wasting, decreased subcutaneous fat, and hair/skin/nail changes suggesting nutritional deficiencies 1
Laboratory Evaluation
- Complete blood count to assess for anemia or infection 1
- Comprehensive metabolic panel including electrolytes, renal function, and acid-base status 1
- Thyroid function tests to evaluate for hypothyroidism 1
- Urinalysis to assess for renal tubular disorders 1
Red Flags Requiring Specialized Evaluation
- Chronic respiratory symptoms (tachypnea, hypoxemia, increased work of breathing) suggest organic etiology 6
- Vomiting, diarrhea, or signs of malabsorption indicate gastrointestinal causes 6
- Hepatomegaly with metabolic derangements suggests metabolic disorders 6
- Dysmorphic features warrant genetic evaluation 6
Common Pitfalls to Avoid
- Do not stop at labeling a child with "FTT"—this provides no actionable information for treatment 3
- Avoid extensive diagnostic workup in all cases; clinical evaluation and anthropometry are most important, as only 1.1% of laboratory tests and 0.4% of imaging studies lead to specific diagnoses 5
- Do not overlook psychosocial causes: inadequate nutrition due to food insecurity, neglect, or behavioral feeding disorders accounts for the majority of cases 5, 3
- Recognize that multiple organ systems often interact—for example, pulmonary disease causing cardiac dysfunction, which then causes renal fluid retention, all contributing to poor growth 6
Treatment Implications
- Most children can be effectively treated in primary care with proper nutrition and family support once the underlying cause is identified 3
- Subspecialist consultation or hospitalization is rarely indicated unless specific organic pathology is identified 3
- Regular follow-up to monitor growth response to interventions is critical after identifying and addressing the underlying cause 1