A Cyanotic Infant: Infrequent Presentation of Cow's Milk Protein Allergy.

We report the case of a three-month-old boy who presented with poor weight gain, loose stools, and poor oral intake for three weeks. Physical examination revealed a pale infant with abdominal distension and cyanosis. Oxygen saturation was normal, but the laboratory showed important methemoglobinemia. The diagnosis of FPIES (food protein-induced enterocolitis syndrome) in the context of cow's milk protein allergy (CMPA) was suspected. Although CMPA is a common condition encountered in small children, chronic forms of FPIES can be difficult to diagnose. Maintaining clinical suspicion about the potential association between methemoglobinemia and gastrointestinal symptoms can lead to prompt recognition and intervention.