Nocardiosis: When the Side Effects of Therapy Mimic Symptoms.

Nocardiosis is a rare infection caused by gram-positive aerobic actinomycetes, which are common in soil. Inoculation occurs by inhaling agent fragments that cause localized or systemic suppurative lesions. The diagnosis is established based on isolation in cultural examinations. Trimethoprim-sulfamethoxazole (TMP-SMX) is the first-line treatment, and an antimicrobial susceptibility test is useful in severe cases or when there is no clinical response. The duration of treatment is determined by the affected site. However, the treatment cycles are long, and recurrence is common, which has a negative impact on the prognosis. We describe a case of an immunocompetent male with a recent diagnosis of pulmonary nocardiosis who, after starting therapy, presented with symptoms that could be explained by either disease progression or an adverse pharmacological reaction. Throughout this case, with atypical evolution, the authors review the diagnostic and therapeutic approach to infection and alert to the importance of the differential diagnosis and available therapeutic options.