Food protein-induced enterocolitis syndrome (FPIES) is a delayed, non-IgE-mediated food allergy. Its major feature is delayed emesis one to four hours after consumption of the triggering food. It is often associated with lethargy, pallor, and diarrhea. It can be difficult to recognize a reaction as FPIES due to the delay of symptoms in association with the triggering food.
FPIES was first described as a delayed enterocolitis illness by Powell in 1976 in two infants that developed a recurring syndrome of vomiting, bloody diarrhea, abdominal distension, septic appearance, and hypothermia after consumption of cow’s milk and soy-based formulas (1).
Since then, a limited number of epidemiologic studies have been conducted, with an incidence range between 0.015% and 0.7% (2, 3, 4, 5). In the United States, the prevalence rate has been estimated at 0.5% of all children (6). These data give further support that FPIES may not be as rare as once thought, and evolving literature indicate rising incidence rates with more foods being implicated (7). Furthermore, with the introduction of guidelines on early peanut introduction, peanut-induced FPIES seems to be increasing in Australia and USA (8, 9). However, given challenges in diagnosis, the true incidence and prevalence of FPIES remain difficult to characterize, and is likely underdiagnosed. These challenges can be partly attributed to unfamiliarity with FPIES due to its relatively new recognition as a syndrome, varying diagnostic criteria and clinical presentations, and geographical differences in FPIES food triggers.
The diagnostic criteria for acute FPIES as defined by Nowak-Wegrzyn et al. in the international consensus guidelines is presented below (Table 1) (10). The gold standard for diagnosis is with an oral food challenge (OFC) with the suspected food. Diagnosis is made clinically, as there are no confirmatory laboratory or imaging tests. Part of the diagnostic challenge with FPIES is that it can present with different phenotypes (10). These include early versus late, acute versus chronic, mild-to-moderate versus severe, solid food FPIES, and atypical FPIES. In atypical FPIES, patients have positive serum IgE, which is associated with a more prolonged course of reactivity (11, 12).
Table 1
Diagnostic criteria for acute FPIES
Major criterion:
|
Minor criteria:
|
Repetitive emesis 1–4 hours after consuming the suspected food, in the absence of classic IgE-mediated allergic skin or respiratory symptoms.
|
1. Repeated episodes of repetitive emesis after eating the same suspected food.
|
|
2. Repetitive emesis 1–4 hours after consuming a different food.
|
|
3. Extreme lethargy.
|
|
4. Pallor.
|
|
5. Need for emergency department visit.
|
|
6. Need for intravenous fluid support.
|
|
7. Diarrhea within 24 hours.
|
|
8. Hypotension.
|
|
9. Hypothermia.
|
To diagnose FPIES, patients must meet the major criterion and ≥ 3 minor criteria.
|
Early versus late FPIES is defined based on age of onset, with the former being younger than 9 months old (10). In acute FPIES, there is intermittent exposure to the food trigger, with resolution of symptoms within 24 hours after eliminating the specific food. Chronic FPIES occurs during daily consumption of the food trigger, and is associated with chronic diarrhea, intermittent emesis, and poor weight gain. Once the food trigger is eliminated, symptoms resolve within 3–10 days. In mild-to-moderate FPIES, symptoms of emesis, diarrhea, pallor, and mild lethargy can be present. In severe cases, hospitalization may be required due to hypothermia, methemoglobinemia, acidemia, and hemodynamic instability. Although FPIES is generally first recognized in infancy once common triggers such as cow’s milk or soy products are introduced, FPIES secondary to solid foods are also seen. While cow’s milk and soy remain the most common food triggers, others such as grains, rice, meats, and fruits are some previously reported solid food triggers for FPIES (13).
There is limited literature on food triggers particularly to solid foods, and on patients diagnosed beyond infancy. We present a case report on acute FPIES in a 12 year old patient, with a late onset of symptoms at age 3, and to a previously unreported FPIES trigger - walnut.