Surgery for Blastomycosis of the Spine

Blastomycosis is a rare fungal infection that primarily produces acute lung infections but may on occasion disseminate to multiple sites, including the skin, bone, central nervous system (CNS), and oropharynx.^1-30 In the case of a primary infection of the lung, if there is a high index of suspicion and a thorough diagnostic workup, the diagnosis can be made from sputum or bronchoscopy.²⁴ Patients present with acute pneumonia that either resolves spontaneously or proceeds to chronic pneumonia with extrapulmonary spread to multiple organs, including the spine. Once vertebral involvement occurs, an untreated infection may result in vertebral body destruction and paraspinal and epidural abscess formation followed by neurologic injury and loss of structural integrity of the spine.^{11,13,17,23,27,29}

In this article, we present a case of blastomycosis of the vertebral body and provide a detailed review of the literature concerning this extremely rare infection of the spine. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 30-year-old African American man with known pulmonary blastomycosis, for which he had been treated with oral itraconazole 200 mg twice daily for 6 months, was admitted to the hospital with a 2-month history of mild thoracolumbar back pain. He reported transient numbness and tingling in the lower extremities but no weakness. He denied weight loss, fatigue, appetite loss, and significant night pain. On physical examination, he was alert and oriented, well nourished, and in no acute distress. Percussion revealed limited range of motion and pain. Further examination of the spine demonstrated no spasm, swelling, erythema, or drainage. The lower extremities had intact sensation, motor strength, reflexes, and pulses, and clonus was absent. White blood cell count was 8100 cells/μL (normal), erythrocyte sedimentation rate was 77 mm/h (normal range, 0-20 mm/h), and C-reactive protein level was 57.2 mg/L (normal, ≤ 10 mg/L). The patient was HIV-negative. Chest radiographs were normal except for a small pleural effusion. Radiographs showed a destructive lesion of T11 with an extensive paravertebral and retropleural abscess tracking a spinal level above and below with extension into the spinal canal (Figure 1).

As the patient had signs of spinal cord compression, he was taken to surgery for incision and drainage and culture procurement and corpectomy of T11 with autogenous rib graft. One week later, he was stabilized with posterior fusion and instrumentation (Figure 2). Gram stain of the specimen demonstrated broad-based budding yeast forms 15 to 20 micrometers in size, consistent with blastomycosis. Cultures were positive for Blastomyces dermatitidis. Histopathologic slides (Figure 3) of the surgical pathology specimen showed granulomatous inflammation. Oral itraconazole 200 mg twice daily was continued, as it has been found to be efficacious in treating immunocompetent patients with blastomycosis¹⁷ and is considered the medication of choice for non–life-threatening, non-CNS blastomycosis. (Intravenous amphotericin B was ruled out because of its known serious side effects, such as bone marrow suppression and renal function impairment¹⁰; itraconazole was the better alternative.) The patient was placed in a thoracolumbar orthosis and discharged. As the effect of presence of instrumentation in the setting of a fungal infection is unknown, it was deemed prudent to maintain the patient on chronic antifungal suppression. One year after surgery, computed tomography (CT) showed solid osseous bridging through the cage crossing the T11 vertebral body, from the inferior endplate of T10 through the superior endplate of T12 (Figure 4). In addition, there had been no recurrence of the spinal infection, and the patient was neurologically intact and doing well.

Discussion

North American blastomycosis (B dermatitidis) is a ubiquitous dimorphic fungus that occurs worldwide and on occasion causes serious infections in humans.^9,23,26,29 It was first characterized in 1894 by Gilchrist and Stokes (Gilchrist disease) when they recovered the fungus from the lung tissue of a patient.³ In North America, blastomycosis infections occur from central Canada to the Gulf Coast to east of the Mississippi River.^{2,5,7,8,13,14,17,21,22,24,27,29} Additional cases of the disease have been reported in Africa,^9,16,23,28 Asia,^12,19 and South America^7,8 (Table [on pages E270-E271]). Recent epidemiologic studies have linked transmission of the disease to bodies of water and have questioned previous reports of male predominance and racial preference for African Americans (Table).

Blastomycosis is acquired when inhaled fungus (airborne conidia spores) causes a primary pulmonary infection or, rarely, when there is direct inoculation through the skin. The differential diagnosis includes neoplasm, tuberculosis, actinomycosis, bacterial infections, cryptococcosis, and coccidioidomycosis.^{3,9,12,20,25,31} Blastomycosis occurs in adults and children.^1-30 The rate of mortality is much higher in immunocompromised patients. Initial symptoms include fever, chills, fatigue, malaise, myalgia, arthalgia, weight loss, and stigmata of chronic disease.^1-30 Acute pulmonary infection with blastomycosis generally resolves spontaneously but may progress to acute respiratory distress syndrome, which has a mortality rate of 50% to 89%.¹⁹ With systemic dissemination, the infection may spread to other organs¹¹—there is a particular predilection for the skin^9,20,29—and to the long bones^7,16 and the oropharynx.^16,26,28