Unusual Presentation of Cow's Milk Protein Allergy

Cow's milk protein allergy (CMPA) is an abnormal immunologic response to bovine protein that can result in various gastrointestinal and cutaneous manifestations including diarrhea, failure to thrive, malabsorption, and even protein-losing enteropathy. We describe a case of a 7-month-old breastfed male who presented with severe atopic dermatitis, emesis, oily diarrhea, failure to thrive, electrolyte disturbance, and hemodynamic instability. Following stabilization, additional evaluation revealed concern for abetalipoproteinemia. Ultimately, the patient's symptoms resolved with introduction of an elemental formula and returned with reinitiation of cow's milk protein, confirming the diagnosis of severe CMPA. It is important for the general practitioner to be aware of the various presentations and have a high index of suspicion for CMPA as no symptom or diagnostic test is pathognomonic for diagnosis. Even though it can mimic other causes of malabsorption, a trial with extensively hydrolyzed or elemental formula should be attempted before undertaking invasive testing.