What are the organic causes of failure to thrive (FTT) in children?

Organic Causes of Failure to Thrive in Children

Organic failure to thrive results from identifiable medical conditions affecting caloric intake, absorption, utilization, or increased metabolic demands, with gastrointestinal, cardiac, and pulmonary disorders representing the most common etiologies. 1

Major Organ System Categories

Gastrointestinal Disorders (Most Common Organic Cause)

Gastrointestinal diseases account for approximately 29% of organic FTT cases and should be the primary focus of evaluation. 1

Structural Malformations

• Esophageal atresia and tracheoesophageal fistula cause feeding difficulties and aspiration risk 2
• Intestinal malrotation, intestinal atresia, anal atresia/stenosis, and imperforate anus 2
• Hirschsprung disease leading to chronic constipation and feeding intolerance 2
• Diaphragmatic, umbilical, and inguinal hernias 2

Functional GI Disorders

• Gastroesophageal reflux disease (GERD) with nasopharyngeal reflux, particularly in infants with structural palate abnormalities 2
• Esophageal dysmotility and gastroparesis 2
• Severe constipation from intestinal dysmotility 2
• Swallowing dysfunction from oromotor coordination problems 2

Malabsorption Syndromes

• Celiac disease and inflammatory bowel disease 2
• Autoimmune enteritis 2
• Pancreatic insufficiency requiring enzyme replacement 3

Cardiac Disorders (Second Most Common)

Cardiac conditions represent 23.4% of organic FTT cases, with heart failure directly causing inadequate growth through multiple mechanisms. 1, 2

• Congenital heart disease with increased metabolic demands 1
• Left ventricular dysfunction causing pulmonary edema and increased work of breathing 2
• Pulmonary hypertension from chronic hypoxemia 2

Pulmonary/Respiratory Disorders

Chronic lung disease accounts for 23.4% of organic FTT, with hypoxemia and increased work of breathing diverting calories from growth. 1, 2

• Chronic lung disease of infancy/bronchopulmonary dysplasia 2
• Chronic hypoxemia increasing metabolic demands 2
• Increased work of breathing and decreased breathing efficiency 2
• Tracheomalacia and laryngeal anomalies 2
• Aspiration pneumonia from swallowing dysfunction 2

Endocrine/Metabolic Disorders

Thyroid Dysfunction

• Hypothyroidism affecting growth velocity 2
• Autoimmune thyroiditis 2

Metabolic Disorders

• Glycogen storage disease type I causing recurrent hypoglycemia, lactic acidosis, and hepatomegaly 2
• Inborn errors of metabolism should be suspected when FTT occurs with specific metabolic derangements 4
• Growth hormone deficiency (rare but responsive to treatment) 2

Electrolyte Disorders

• Hypocalcemia causing feeding difficulties and irritability 2

Renal/Genitourinary Disorders

Renal dysfunction contributes to FTT through fluid retention, electrolyte imbalances, and direct effects on growth. 2

• Hydronephrosis and obstructive uropathy 2
• Unilateral renal agenesis or multicystic dysplastic kidney 2
• Vesicoureteral reflux 2
• Renal tubular disorders detected on urinalysis 5
• Decreased renal function causing sodium/water retention 2

Neurologic Disorders

Neurologic conditions affect FTT through multiple pathways including feeding coordination, muscle tone, and metabolic regulation. 2

• Global hypotonia causing feeding difficulties and decreased oral intake 2
• Polymicrogyria and cerebellar abnormalities 2
• Swallowing dysfunction from CNS dyscoordination 2
• Chronic hypoxemia affecting neurodevelopment 2
• Developmental delay affecting feeding skills 2

Genetic/Chromosomal Disorders

Genetic syndromes frequently present with FTT as a cardinal feature, often with multiple contributing organ system abnormalities. 2

• 22q11.2 deletion syndrome with feeding difficulties, cardiac defects, and hypocalcemia 2
• Cardio-facio-cutaneous syndrome with severe feeding difficulties and gastroesophageal reflux 2
• Skeletal dysplasias requiring enteral nutrition in 50% of cases 6
• Shwachman-Bodian-Diamond syndrome with feeding difficulties in 48-73% 6

Hematologic Disorders

• Anemia reducing oxygen delivery and energy availability 5
• Chronic infection from immunodeficiency 2

Key Clinical Distinctions

Organic FTT is characterized by lower gestational age, lower birth weight, younger age at diagnosis, and more severe Z-score deficits compared to non-organic causes. 7

Red Flags for Organic Etiology

• Prematurity and low birth weight 7
• Congenital anomalies 1
• Chronic respiratory symptoms (tachypnea, hypoxemia, increased work of breathing) 2
• Vomiting, diarrhea, or signs of malabsorption 2
• Hepatomegaly with metabolic derangements 2
• Cyanosis or signs of cardiac disease 1
• Dysmorphic features suggesting genetic syndromes 2

Important Clinical Caveats

Routine laboratory screening identifies organic causes in less than 1.4% of cases when history and physical examination are unrevealing. 8 Therefore, extensive testing should be reserved for children with specific clinical indicators or those failing to respond to nutritional intervention 8, 7.

The majority of non-organic FTT cases (88%) do not require extensive blood work or specialist consultations when a systematic clinical approach is used. 7

Multiple organ systems often interact to cause FTT—for example, pulmonary disease causing cardiac dysfunction, which then causes renal fluid retention, all contributing to poor growth. 2