Milk-related food-dependent exercise-induced anaphylaxis with suspected pork-cat syndrome in an 11-year-old boy

Pork-cat syndrome (PCS) is caused by cross-reactivity between cat serum albumin (Fel d 2) and pork serum albumin (Sus s 1). Although bovine serum albumin (Bos d 6) is also homologous to Fel d 2, milk-related symptoms have rarely been described in patients with PCS. We report an 11-year-old boy with food-dependent exercise-induced anaphylaxis (FDEIA) in whom milk was identified as the trigger and serum albumin cross-reactivity was suspected as a possible mechanism. He had experienced two episodes of anaphylaxis after eating pork sausage for breakfast and school lunch containing milk and pork, followed by exercise. He had lived with a cat since birth. Serum testing showed high levels of specific IgE to Fel d 2, Sus s 1, Bos d 6, cat dander, pork, beef, and milk, whereas casein-specific and alpha-gal-specific IgE levels were low. Skin prick testing was positive for raw pork, raw beef, pork sausage, and unheated milk, but negative for heated pork, heated beef, and heated milk. In an oral food challenge, symptoms were reproduced after exercise following ingestion of 300 mL of unheated milk, leading to a diagnosis of milk-related FDEIA. Inhibition enzyme–linked immunosorbent assay demonstrated partial inhibition of IgE reactivity to Bos d 6 by pork, cat hair, and milk extracts at the tested concentration. These findings suggested serum albumin cross-reactivity involving PCS. This case highlights the clinical utility of component-resolved diagnosis, particularly low casein-specific IgE with high Bos d 6–specific IgE, in raising suspicion of serum albumin-related mechanisms in patients with milk-related FDEIA.