Indolent nonendemic central nervous system histoplasmosis presenting as an isolated intramedullary enhancing spinal cord lesion

Abstract

Background: Histoplasma capsulatum infection is largely seen in endemic regions; it results in symptomatic disease in <5% of those infected and is most often a self-limiting respiratory disease. Disseminated histoplasmosis is considered rare in the immunocompetent host. Central nervous system (CNS) dissemination can result in meningitis, encephalitis, and focal lesions in the brain and spinal cord, stroke, and hydrocephalus. An intramedullary spinal cord lesion as the only manifestation of CNS histoplasmosis has been rarely described.

Case description: We present an atypical case of a 44-year-old man from a nonendemic region, on adalimumab therapy for ulcerative colitis who developed an isolated intramedullary spinal cord lesion in the setting of disseminated histoplasmosis. His course was initially indolent with vague systemic symptoms that led to consideration of several other diagnoses including sarcoidosis and lymphoma. Biopsies of several positron emission tomography positive lymph nodes revealed granulomatous inflammation, but no firm diagnosis was achieved. He was ultimately diagnosed with histoplasmosis after an acute respiratory infection in the setting of anti-tumor necrosis factor therapy. With appropriate antifungal therapy, the spinal cord lesion regressed. The previous systemic biopsies were re-reviewed, and rare fungal elements consistent with H. capsulatum were identified. A presumptive diagnosis of CNS histoplasmosis was made in the absence of direct laboratory confirmation in the setting of rapid and complete resolution on antifungal therapy.

Conclusion: Disseminated histoplasmosis should be considered in granulomatous disease, even if the patient resides in a nonendemic region. Furthermore, clinicians should be mindful that CNS histoplasmosis may present in an atypical fashion.

Keywords: Abscess; Central nervous system; Histoplasmosis; Intramedullary; Spinal cord.

Figure 1:

Fluorodeoxyglucose-positron emission tomography imaging demonstrates areas of hypermetabolism in the right subaxillary lymph nodes (a), left lingual tonsil (b), and T3 region of the spinal cord (c).

Figure 2:

Initial magnetic resonance imaging of the thoracic spine demonstrates a 9-mm homogeneously-enhancing intramedullary spinal cord lesion with significant edema within the spinal cord above and below the lesion. Sagittal T2-weighted image (a), sagittal T1-weighted image without contrast (b), and sagittal T1-weighted image without contrast (c) are shown.

Figure 3:

Follow up serial sagittal T1-weighted magnetic resonance imaging of the thoracic spine with contrast – 3 months (a), 6 months (b), and 10 months (c) from initial imaging [Figure 2c] – demonstrate interval regression and ultimate resolution of the enhancing intramedullary spinal cord lesion.

Figure 4:

Follow-up sagittal T2-weighted MRI of the thoracic spine at 10 months. Significant improvement in spinal cord edema compared to initial imaging [Figure 2a].

Figure 5:

Hematoxylin and eosin (H&E) (a) and Grocott methenamine silver (GMS) special stain (b) (×400) of the necrotizing granuloma in the left tonsil. H&E (c) and GMS special stain (d) (×400) of the non-necrotizing granuloma in the abdominal wall. A few GMS-positive fungal microorganisms are identified that are morphologically consistent with histoplasma.