Coccidiomycosis presenting as a popliteal cyst

Case Report

Coccidiomycosis Presenting as a Popliteal Cyst Daniel C. Wascher, M.D., Gregg P. Hartman, M.D., Carl Salka, M.D., and Gregory J. Mertz, M.D.

Summary: Coccidiomycosis is a fungal infection that primarily causes pulmonary disease. Extrapulmonary dissemination can occur to the musculoskeletal system with the knee joint most frequently involved. This case report describes a patient with coccidiomycosis whose initial presentation was of a popliteal cyst. The need for aggressive surgical and antibiotic treatment to eradicate this infection is discussed. Coccidiomycosis should be considered in a differential diagnosis of patients with popliteal cysts without other obvious etiologies. Key Words: Coccidiomycosis—Popliteal cyst—Septic arthritis.

C

occidiomycosis is an infection caused by the fungus Cocccidioides immitis, a dimorphic fungus endemic to the southwestern United States, Central America, and parts of South America. Infection with C. immitis primarily causes pulmonary disease with extrapulmonary dissemination occurring in fewer than 1% of patients.1 When extrapulmonary dissemination occurs, the most common sites of infection are the skin, meninges, and the skeletal system.2,3 However, dissemination can occur in almost any organ system. Septic arthritis usually occurs secondary to direct extension from infected adjacent bone,4 but primary synovial coccidiomycosis can also occur.5 The knee is the most frequently involved joint.1 Most patients with orthopaedic manifestation have known pre-existing pulmonary coccidiomycosis or symptoms such as cough, dyspnea, and chest pain.6 We report on an unusual presentation of a 31-year-old man whose initial presentation of coccidiomycosis was a popliteal cyst.

From the Division of Sports Medicine, Department of Orthopaedics (D.C.W., G.P.H.), and the Division of Infectious Diseases, Department of Internal Medicine (C.S., G.J.M.), the University of New Mexico, Albuquerque, New Mexico, U.S.A. Address correspondence and reprint requests to Daniel C. Wascher, M.D., 2211 Lomas Blvd, NE, Albuquerque, NM 871315296, U.S.A. r 1998 by the Arthroscopy Association of North America 0749-8063/98/1401-1754$3.00/0

CASE REPORT A 31-year-old Caucasian man presented with a chief complaint of increased stiffness in his left knee and a mass behind the knee for the previous 4 months. He denied any history of trauma or previous knee swelling. The patient had no fever, cough or shortness of breath. He had no significant medical or surgical history. The patient was not immunocompromised. His only travel outside of New Mexico in the past 10 years had been to Arizona 1 year earlier. Physical examination of the left knee showed a range of motion from 0° to 130°. There was no knee effusion and the joint was not tender. There was no ligamentous instability. A large cystic mass (6 ⫻ 8 cm) was palpable in the patient’s popliteal fossa. Neurovascular examination was unremarkable. Knee radiographs showed normal osseous structures. To search for an intra-articular cause for the popliteal cyst, a magnetic resonance image was obtained that showed a large popliteal cyst without any additional extraarticular or intra-articular pathology (Fig 1). A preoperative chest radiograph was not obtained. The patient underwent left knee diagnostic arthroscopy, which showed a normal appearing synovium. A small indentation in the capsule was noted in the posterior-lateral joint. The patient was turned prone and a 8 ⫻ 6 ⫻ 4 cm cyst was excised through a direct posterior approach. The stalk of the cyst communi-

Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 14, No 1 (January-February), 1998: pp 99–102

99

100

D. C. WASCHER ET AL. cated with the posterior-lateral capsule. Routine pathology was performed on the surgical specimen. Histological examination revealed fungal elements diagnostic for coccidiomycoses (Fig 2). Further evaluation included a computed tomographic scan of the head, chest radiograph, and a lumbar puncture, all of which were normal. A bone scan showed uptake only in areas of previous trauma in the left proximal ulna and right elbow. The patient was not tested for the human immunodeficiency virus, but a complete blood count was normal. At 10 days after the operation, the left knee had a 3⫹ effustion that was aspirated and sent for fungal cultures. These cultures were positive for C. immitis. Serum IgG antibodies to C. immitis were detected by complement fixation at a dilution of 1:8.7 The patient was initially treated with oral fluconazole, 400 mg daily, and was later enrolled into a blinded, randomized study for treatment of nonmeningeal disseminated coccidiomycoses. He was treated for 12 months with either oral fluconozole (400 mg daily) or itraconozole (200 mg twice daily). The blinding had not been revealed at the time of this writing. Cultures of the left knee joint after completing treatment were negative for fungal growth. Serum antibody titers were negative at a 1:1 dilution 4 months after initiating treatment and remained normal over the course of of 1 year. When last seen, the patient has no complaints of left knee pain or swelling. DISCUSSION

FIGURE 1. (A) Sagittal and (B) axial T2 weighted magnetic resonance images of the knee showing a large popliteal cyst with communication to the posterior-lateral joint capsule. Note the small effusion in the knee joint and the lack of any osseous changes.

This case is an unusual presentation of coccidiomycosis for several reasons. First, our patient had no previous or current pulmonary manifestations and a normal chest radiograph. Most patients who develop coccidial bone or joint infections have known pulmonary disease, although it has been previously noted that patients with normal pulmonary findings can have extrapulmonary dissemination.1 Secondly, our patient had no evidence of being immunocompromised. In a recent series of 24 patients with orthopaedic C. immitis infection, 11 were immunocompromised.1 As more patients are rendered immunocompromised by disease and medical treatment, the incidence of disseminated coccidiomycosis may increase. Finally, our patient had primary coccidioidal synovitis occurring within a popliteal cyst. Most joint infections involving C. immitis occur by direct invasion from contiguous bone involvement. When primary synovitis occurs, the mechanism is thought to be hematogenous seeding.5 A literature search found only two other cases of

COCCIDIOMYCOSIS PRESENTING AS POPLITEAL CYST

101

FIGURE 2. Photomicrographs of the excised popliteal cyst wall at high magnification (⫻450). (A) H&E stain showing coccidiodes spherules with endospores in a granuloma. (B) Gamori methenamine silver stain shows uptake of the stain in the cell wall that confirms the fungal organism.

coccidomycosis causing a popliteal cyst. In one case,8 the patient’s initial presentation was for a mass in the posterior knee region. This patient also was noted to have a large knee effusion and radiographic changes of the tibia. The authors theorized that the knee joint was seeded by a fungal abscess in the lateral tibial plateau with subsequent formation of a popliteal cyst. The second case9 was similar to ours in that the patient presented with a large synovial cyst without a knee effusion and with normal radiographs. However, 6 months later that patient did develop a knee effusion and was found to have acute synovitis on arthrotomy performed at the time of cyst removal. Popliteal cysts can occur from a variety of conditions. Most commonly, popliteal cysts occur in patients with intra-articular lesions such as rheumatoid arthritis, osteoarthritis, or meniscal tears. It is thought that synovitis and increased joint fluid production causes joint fluid to leak into the gastrocnemiussemimembranosus bursa.10 Any condition that can cause synovitis has been associated with popliteal cysts. Baker, whose name has become associated with popliteal cysts, noted in 1877 that most cases of popliteal cysts were caused by tuberculosis.10 Although coccidiomycosis is certainly an unusual cause of a popliteal cyst, an index of suspicion is prudent in a patient with a large cyst with no obvious intra-articular pathology. In such instances aspiration of the cyst for synovial fluid analysis and culture can aid in planning treatment. The treatment of muskuloskeletal coccidioidomycosis is evolving. Traditionally it was believed that joint arthrodesis or amputation was often necessary to eradicate the infection.11 With the advent of antifungal antimicrobials, joint infections were often successfully

treated with synovectomy and systemic or intraarticular amphotericin B.5,12 However, amphotericin B was associated with severe side effects that often limited its usefulness. The imadazoles are a new class of antifungal agents that are effective against C. immitis. Despite these new pharmacological agents, patients treated with combined surgical and medical treatment have a better chance of cure than treatment with medical therapy alone.1,13,14 Several cases have been reported with recurrence of the disease many years after apparent cure.7,13 Serological testing to follow complement fixation titers is useful to monitor response to treatment and to identify recurrence. Thus, the current recommended treatment for muskuloskeletal coccidioidomycosis remains early surgical debridement, long-term antifungal therapy, and serological monitoring. Our patient has had an excellent response to excision of the popliteal cyst, arthroscopic lavage and antifungal therapy. His serological test results are currently normal, but he has been cautioned that the disease may recur. This case illustrates several important points. First, coccidiomycosis should be considered as a cause of a popliteal cyst without obvious intra-articular pathology. Orthopaedic C. immitis infection can occur without obvious pulmonary involvement. Successful treatment of joint involvement requires a combination of surgical synovectomy and long-term antifungal therapy. Response to treatment can be monitored by serological complement fixation titers. REFERENCES 1. Bried JM, Galiani JN. Coccidiodes immitis infections in bones and joints. Clin Orthop 1986;211:235-243.

102

D. C. WASCHER ET AL.

2. Drutz DJ, Cantanzaro A. Coccidioidomycosis: Part 1. Am Rev Respir Dis 1978;117:559-585. 3. Drutz DJ, Cantanzaro A. Coccidioidomycosis: Part 2. Am Rev Respir Dis 1978;117:727-741. 4. Dalinka MK, Dinnenberg S, Greendyke WH, et al. Roentgenographic features of osseous coccioidomycosis and differential diagnosis. J Bone Joint Surg Am 1971;53:1157-1164. 5. Rettig AC, Evanski PM, Waugh TR, et al. Primary coccidioidal synovitis of the knee. A report of four cases and review of the literature. Clin Orthop 1978;132:187-192. 6. Worrell RV. Infectious diseases of bone. In Bronner F, Worrell RV, eds. A Basic science primer in orthopaedics. Baltimore: Williams & Wilkins, 1991;227-235. 7. Wieden MA, Galgani JN, Pappagianis D. Comparison of immunodiffusion techniques with standard complement fixation assay for quantitation of coccidioidal antibodies. J Clin Microbiol 1983;18:529-534.

8. Bried JM, Benjamin JB, Galiani JN. Coccidiodes immitis: An unusual presentation. Orthopedics 1990;13:345-347. 9. Aidem HP. Intra-Articular amphotericin B in the treatment of coccidiodal synovitis of the knee. J Bone Joint Surg Am 1968;50:1663-1668. 10. Wigley RD. Popliteal cysts: Variation on a theme of Baker. Semin Arthritis Rheum 1982;12:1-10. 11. Winter WG, Larson RK, Honeggar MM, et al. Coccidioidal arthritis and its treatment. J Bone Joint Surg Am 1975;57:11521157. 12. Pollock SF, Morris JM. Coccidioidal synovitis of the knee. J Bone Joint Surg Am 1967;49:1397-1407. 13. Lantz B, Selakovich WG, Collins DN, et al. Coccidioidomycosis of the knee with a 26-year follow-up examination. Clin Orthop 1988;234:183-187. 14. Smith JW, Alder L, Goodrich D. Successful therapy of coccidioidomycosis of the knee with fluconazole. Orthopedics 1995;18:191-192.