According to the CCS, a patient with grade 2 or higher CIMDL with no history of drug snorting should undergo a complete workup to search for autoimmune, infection, or tumoral lesions using serology (ESR, ANA, C-ANCA—with immunofluorescence for NPO and PR3 if positive—IgG4, and rheumatoid factor), rheumatology/internal medicine and infectious disease consultation, and nasal biopsy. This evidence concerns the gene PRTN3 and infectious disease.