Drug desensitization in 17-year-old male with Mast Cell Activation Syndrome, pneumonia, and antibiotic hypersensitivities.

Rapid desensitization (RD) is utilized in order to provide necessary medications to patients with drug hypersensitivity. RD is performed in a closely monitored setting to protect patients from severe anaphylactic or anaphylactoid reactions. A recently classified syndrome, mast cell activation syndrome (MCAS), has been defined by episodic symptoms caused by mast cell mediators and is associated with specific laboratory markers. Patient with MCAS and history of systemic reactions to ceftriaxone and azithromycin presented with pneumonia requiring treatment with ceftriaxone and azithromycin, both provided via desensitization protocols. Desensitization for drug hypersensitivities in the setting of MCAS presents several controversial issues as mechanism of hypersensitivity may not be related to IgE-mediated but rather non-specific mast-cell degranulation. The controversies of diagnosis and management of antibiotic hypersensitivity in patients with MCAS discussed. Our case demonstrates that desensitization protocols can be used in MCAS patients with noted hypersensitivities. The intricacies of desensitization in the setting of MCAS are not fully understood and will require further research and characterization.