Paper Title
Atypical Temporal Evolution of Disseminated Nocardiosis in an Immunocompetent Host: A Diagnostic Challenge

Abstract
This paper presents the case of an immunocompetent male in his late forties with cerebral and pulmonary nocardiosis. Nocardiosis is an uncommon but serious bacterial infection caused by nocardia species, which are aerobic, gram positive, partially acid-fast, filamentous bacteria found in soil, decomposing vegetation, and other organic matter. The pathogen is generally considered opportunistic, causing infections mostly in immunocompromised people, although cases in immunocompetent hosts are not uncommon. The clinical forms of nocardiosis include pulmonary, central nervous system, cutaneous, and disseminated infections. We describe the case ofa48-year-old male, working in a meat factory, presented to us with complaints of headachefor 20 days which was followed byleftsided facial weakness, leftsided hemiparesis, ataxia, and cognitive dysfunction for last 15 days. His initial workup revealed anaemia, elevated ESR, normal CXR and an MRI brain showing a space-occupying lesion (SOL) in the left posterior parietal region with imaging suggestive of either infection or neoplasm. In spite of initial treatment with piperacillin-tazobactam, steroids, and mannitol in an outside hospitalover 2 weeks, there was only partial relief in the initial symptoms, and thereforerepeat brain imaging was donewhich revealed no change in the size of the lesion. Hence a PET-CT was done which showed FDG-avid lesions in the brain with no FDG avid lesion elsewhere. Later patient started having pulmonary symptoms and complained of gradually progressing cough for 7 days following which a repeat chest imaging was done which showed nodular mass in the right lower lobe. CT guided lung biopsy of the lesion was performed, histopathological examination and culture from the tissue biopsy revealed it to be nocardia. Patient was started on trimethoprim-sulfamethoxazole, Injection Meropenem and Injection Amikacin and there was prompt clinical improvement along with radiological resolution of the pulmonary lesion. This case highlights an unusual presentation of nocardiosis with primary CNS involvement in an immunocompetent individual followed by delayed pulmonary manifestation. The absence of initial pulmonary findings and the radiological resemblance to neoplastic lesions contributed to diagnostic delay. Early consideration of nocardiosis in atypical brain lesions, even in immunocompetent hosts is essential to avoid misdiagnosis and initiate timely therapy.