Food Protein-Induced Enterocolitis Syndrome (FPIES) Characteristics and Diagnosis
Clinical Features
- FPIES is a non-IgE-mediated food allergy that causes severe, delayed gastrointestinal reactions characterized by profuse, repetitive vomiting starting 1-4 hours after eating a trigger food, often accompanied by lethargy, pallor, and potentially life-threatening dehydration or shock 1, 2
- Vomiting onset begins 1-4 hours after ingestion, with a character of profuse, projectile, repetitive vomiting, often bilious with dry heaving 1, 3, 4
- Associated symptoms include marked pallor, lethargy progressing to extreme lethargy, decreased activity level, and diarrhea developing in many cases within 5-10 hours 1, 3, 4
- Severe presentations can include dehydration requiring IV fluids 1, hypothermia 6, metabolic acidosis 6, methemoglobinemia 5, and abdominal distention 5
Pathophysiology and Trigger Foods
- FPIES is classified as a non-IgE-mediated food allergy, involving antigen-specific T cells, cytokines, and intestinal inflammation affecting the colon and ileum 6, 7, 8
- Common trigger foods include cow's milk, soy, rice, and oat, with geographic and age-related patterns existing 1, 3
- Infants under 6 months are more likely to react to cow's milk and soy formula, while infants 6-12 months are more likely to react to solid foods like rice and oat 1, 3
Diagnosis and Laboratory Findings
- Diagnosis is primarily clinical, based on characteristic history, with major and minor criteria, including vomiting 1-4 hours after suspect food ingestion without classic IgE-mediated allergic skin or respiratory symptoms 3, 4, 5
- Laboratory findings are supportive, not diagnostic, and include increased white blood cell count with neutrophilia, thrombocytosis, stool positive for leukocytes or increased carbohydrate content, and metabolic acidosis in severe cases 1, 3, 5
- IgE testing is typically negative, though atypical cases exist 6, 7
Epidemiology and Natural History
- FPIES is not rare, with a cumulative incidence in infants of 0.34% and a population prevalence in US infants of 0.51% 2
- Typical onset is 2-7 months of age when formula or solid foods are introduced 1, 3
- Most infantile FPIES resolves over time, with a generally favorable prognosis for cow's milk, soy, and grain triggers 7