A 6-year-old boy (new patient) presents to your clinic with wheezing. Per parents, he is on Fluticasone Propionate/Salmeterol (Advair® HFA), 2 puffs twice daily (total 460 mcg fluticasone/day) and montelukast. He also uses albuterol as needed. In the past 12 months, he has been to the ER 10 times for wheezing and given inhalers and oral medications. Three of the ER visits resulted in prolonged hospital stays for a “lung infection,” and he is “always sick”. Other than asthma, he has no medical problems that they are aware of. Parents also state that he is UTD on all his vaccines except for his 4-year vaccines. Parents have been hearing more about Tetanus and want to ensure that he is immune.

On physical examination, he exhibits diffuse wheezing, which improves with albuterol and oral steroids in the office. He is sent home with an oral steroid burst, albuterol, and continuation of Advair. The rest of the ROS and physical exam are negative, and he has a normal height and weight.

Initial labs and imaging are completed CBC with Diff: elevated eosinophils at 300 cells/μL Reassuring CMP Immunoglobulins: normal IgE and IgM, lower IgG (<2 standard deviations below the norm), low IgA Tetanus non-immune Chest x ray: normal

Two months later, the family returns and wants to discuss labs and additional medications for his symptoms. What labs should be drawn at this visit? Please include both visit specific labs and any follow-up labs needed from the last appointment. Based on the patient’s history, presenting symptoms, and available lab work, what is the most likely diagnosis? What is the most appropriate medication to start immediately, and what other medications and treatments should be considered? Information should be based on the latest peer-reviewed medical literature as of May 2025.