This conference revisits prior pulmonary cases, including a young patient with cavitary lung lesions growing mucoid Klebsiella pneumoniae with a strongly positive serum cryptococcal antigen, and another young patient with a new cavitary lung lesion and low-positive Coccidioides complement fixation after travel and housing exposures. These updates emphasize how follow-up imaging, incomplete outpatient follow-up, and low-titer fungal serologies complicate diagnostic closure.
The new case focuses on an immunocompromised patient with untreated T-cell large granular lymphocytic leukemia and steroid exposure who presented with altered mental status, hypoxia, hyponatremia, viral respiratory PCR positives, a positive urine Legionella antigen, and a cavitary pulmonary lesion with a halo sign. The teaching portion uses this case to review Legionella beyond “atypical pneumonia,” including hyponatremia, renal tubular/Fanconi-like abnormalities, coinfections, and when a positive urine antigen may or may not explain the full radiographic syndrome.