MON-235 Mycobacterium Fortuitum Infection Mimicking Sellar Chondrosarcoma in a Non-Immunosuppressed Patient: An Unusual Cause of Hypopituitarism and Oculomotor Nerve Palsy

Abstract

A 32-year old male patient of central African origin presented with diplopia and left eyelid ptosis. He described a 2-month history of fatigue, weight loss (8 Kg), headaches, diffuse myalgia and night sweats. Clinical examination revealed cavernous sinus syndrome with left eyelid ptosis and weakness of eye adduction. Magnetic resonance imaging of the brain demonstrated a 36 mm mass centered on the left petroclival suture, infiltrating the sella and the pituitary gland, the ipsilateral orbital apex as well as the cavernous sinus bilaterally. The mass showed heterogenous enhancement after gadolinium injection, with elements of central necrosis and was associated with an extensive bone destruction. These radiologic features raised the hypothesis of chondrosarcoma. Chest computed tomography demonstrated multiple lung micro-nodules suspect of metastasis. Laboratory testing of the anterior pituitary function revealed low free-T4 (11 pmol/l, n = 12-22) with normal TSH (0.4 mUI/l, n=0.3-4.2), low total testosterone (1.5 ugr/l, n = 3.3-8.1) with normal LH and FSH and slight hyperprolactinemia (27 ugr/l, n = 4-15). IGF-1, 24-h urinary free cortisol, as well as morning serum cortisol and cortisol after 250 mcg ACTH stimulation test were normal. There was no evidence of diabetes insipidus. Levothyroxine was prescribed. Craniotomy was performed, for left optic nerve decompression and biopsy of the mass. Pathologic examination revealed granulomatous, giganto-cellular and necrotizing inflammation, but no evidence of malignancy. PCR for Mycobacterium tuberculosis complex was negative but Mycobacterium fortuitum was detected in sputum and also confirmed in cerebral biopsy latter. Other causes of granuloma were excluded (brucellosis, cat scratch disease, histoplasmosis, syphilis, coccidioidomycosis, tropical germs etc.). Different causes of immunosuppression (including HIV) were excluded. The patient was treated with amikacin, isoniazid and ciprofloxacin for several months and improved gradually. MRI performed one year later demonstrated significant decrease on the size of the sellar mass (more than 50% of its initial size). Central hypogonadism regressed spontaneously with decrease in tumor size, and normal testosterone levels were achieved at one-year follow-up (7 ugr/l, n = 3.3-8.1). Mycobacterium fortuitum infections of the sella turcica are poorly described in literature in non-immunosuppressed individuals. Although usually not pathogenic, histopathological examination, identification in the CNS lesion and the lungs and response to treatment are convincing evidence of a causal relationship. Differential diagnosis from malignant lesions is challenging and biopsy is necessary in order to establish the cause and offer adequate treatment.