Suspected Macrolide-Refractory Mycoplasma pneumoniae Pneumonia With Discordant Coccidioides Serology in an Immunocompromised Host: A Case Report.

Suspected macrolide-refractory Mycoplasma pneumoniae pneumonia can be a diagnostic challenge in immunocompromised hosts, particularly after allogeneic stem cell transplantation. Screening serologies may further complicate diagnosis when false-positive or discordant results divert therapy. We report a 63-year-old woman with B-cell acute lymphoblastic leukemia status postallogeneic stem cell transplantation and hypogammaglobulinemia who was transferred for persistent cough, exertional dyspnea, and right upper-lobe consolidation after limited improvement with azithromycin and broad-spectrum antibacterial therapy. Initial and repeat respiratory testing detected M. pneumoniae, while an extensive infectious evaluation was otherwise negative. Coccidioides enzyme immunoassay IgM and IgG were positive, prompting empiric fluconazole, but confirmatory immunodiffusion and complement fixation testing were negative, and the patient lacked epidemiologic risk factors. Following reassessment, fluconazole was discontinued; doxycycline and replacement intravenous immunoglobulin were initiated. Clinical improvement followed, including discontinuation of supplemental oxygen and return to baseline exercise tolerance, although the relative contributions of doxycycline and intravenous immunoglobulin cannot be determined from a single case. This case highlights the need to interpret screening fungal serologies in a clinical and epidemiologic context, confirm positive Coccidioides EIA results, and consider clinically suspected macrolide-refractory M. pneumoniae when respiratory symptoms persist despite macrolide therapy. Molecular resistance testing was not available, so macrolide resistance remained clinically suspected rather than proven.