Heiner Syndrome (HS) is a rare non-IgE mediated hypersensitivity reaction to cow’s milk resulting in chronic respiratory disease due to pulmonary hemorrhage. Heiner et al. first described this entity in 1962 after identifying cow’s milk precipitins (immunoglobulin G to milk antigens) in the sera of seven children with chronic respiratory symptoms and infiltrates on chest radiograph 2. Associated findings include gastrointestinal symptoms, anemia, recurrent fever, and growth faltering. Removal of milk protein from the diet leads to symptom resolution and reversal of chest radiograph findings. Children with HS often experience delays in diagnosis given its rarity, chest imaging that can mimic infectious pneumonia, and variable clinical and laboratory features 3. Milk precipitin testing, for example, is not positive in all cases 4. Special attention should be paid to chest radiography as a recent review of HS cases found that pulmonary infiltrates were universal in this condition (with the exception of one study that did not include radiography data) 5. The rapid evolution of the patient’s symptoms and imaging, despite negative testing, highlight the importance of expanding the differential diagnosis for patients with pulmonary infiltrates that do not respond to typical treatments to include HS.