Suppurative thyroiditis: Coinfection by Nocardia spp. and Mycobacterium Tuberculosis in an immunocompromised patient

Abstract

Abstract Suppurative thyroiditis (ST) is a rare entity with an incidence of 0.1–0.7% of thyroid diseases. The resistance to infection of the thyroid gland is explained by its encapsulated position, high blood flow, bactericidal action of iodine and extensive lymphatic network. Clinically, ST manifests with pain, fever, erythema, and dysphonia, usually with preserved thyroid function. Fine-needle aspiration is preferred for diagnosis because it not only allows microbiological sampling, but also therapeutic drainage and differentiation with subacute thyroiditis in cases of thyrotoxic. Regarding its etiology, it is most caused by Gram-positive bacteria, mainly Streptococcus and Staphylococcus. Among the Gram-negative, Salmonella is the most isolated. Regarding opportunistic microorganisms, Mycobacterium tuberculosis has a prevalence between 9.3–16%, while Nocardia represents 4%. Nocardia can spread hematogenously to any organ with tropism to the central nervous system and infrequently to the thyroid. It is characterized by abscess formation and chronic progression with relapses despite adequate treatment. Diagnosis requires clinical suspicion and microbiological isolation with an incubation time of up to 14 days, imaging studies are nonspecific and may show abscesses, thyroid scintigraphy is usually abnormal, with evidence of cold nodules. Infections in the thyroid gland are infrequent due to Mycobacterium tuberculosis even in areas where it is endemic; it presents a frequency of 0.1–0.4% of all cases of tuberculosis with a varied range of presentation as solitary nodule, diffuse or multinodular goiter. We present the first report in the literature of an immunocompromised patient with suppurative thyroiditis in coinfection by Nocardia and Mycobacterium tuberculosis.