Mycobacterium kansasii causing carpal tunnel syndrome with concomitant pulmonary mycobacterium tuberculosis infection.

ABSTRACT

Mycobacterium kansasii is an uncommon cause of infection of the hand. Other atypical mycobacteria that cause hand infections are M marinium, M avium, M intracellularis, and M chelonei. Such infections usually occur around aquatic areas, though sometimes the source of infection is elusive. Inoculation of the atypical mycobacterium into the host occurs usually from a traumatic break in the skin. Patients commonly report a history of fish tank cleaning, oyster shucking, swimming, or other aquatic activities. Several drug regimens have been suggested and used successfully. Surgical intervention is occasionally required for unresponsive or symptomatic cases. Concomitant hand infection and pulmonary tuberculosis is extremely rare. We present a case report of M kansasii infection of the hand and forearm, with carpal tunnel syndrome complicated by concomitant pulmonary M tuberculosis.

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ATYPICAL mycobacterial infections of the hand are uncommon in most healthy persons. Mycobacterium marinum and Mycobacterium kansasii are the atypical mycobacteria that most commonly cause hand infections. (1) Various conservative treatment methods have been used effectively in some patients, but there appears to be no consensus on the antibiotic of choice, duration of therapy, or timing of surgical intervention. We present a patient who had carpal tunnel syndrome due to a forearm mass, a history of hand trauma in an aquatic environment, and concomitant pulmonary tuberculosis. This dual infection is rarely described in the literature.

CASE REPORT

A 60-year-old white man presented a 12-month history of increasing swelling in the distal right forearm. The patient works as a commercial fisherman and has frequent minor traumatic punctures and lacerations to the hands. One month before presentation, the patient began to have symptoms of median nerve compression with paresthesias of the thumb and the index and middle fingers. Physical examination revealed a large soft, fixed mass in the distal forearm (Fig 1). A positive Tinel sign was easily elicited over the area of the mass. Carpal tunnel decompression was done, with isolation of the median nerve (Fig 2). The mass, which consisted of flexor tendon synovium and multiple 1- to 2-cm "nodules" of inflammatory synovium, was excised (Fig 3). The patient was treated with rifampin immediately after operation. Stains for acid-fast bacilli as well as routine Gram stains and culture were negative. Lowenstein-Jensen media cultures at 7 weeks revealed M kansasii. After operation, the patient had a positive PPD test, and a lung nodule was found on chest radiograph. The lung nodule was biopsied and was positive for M tuberculosis. Treatment with ethambutol and isoniazid was started after the diagnosis of pulmonary tuberculosis was made. The nerve compression symptoms were relieved, and the patient regained full function of hand and wrist (Figs 4 and 5).

DISCUSSION

As reported by Hurst et al, (2) Aronson was the first to isolate an atypical mycobacterium in 1926. Atypical mycobacterium was first found to cause human disease in 1954 by Norden and Linell when it was isolated from skin lesions associated with a contaminated swimming pool in Sweden. (2) Today, atypical mycobacterial hand infections are more frequently reported than those caused by Mycobacterium tuberculosis. (1)

The key to diagnosis is a high index of suspicion and a thorough patient history. Contact activities in or around aquatics, both seawater and freshwater, can usually be elicited from the patient. Trauma to the hand, including minor puncture wounds and lacerations or more significant injuries, are a common predisposing factor, though occasionally there may be no history of trauma. (3) Signs and symptoms include soft, tender or nontender masses of the flexor or extensor tendons representing tenosynovitis. Limitations of flexion or extension due to a mass effect or pain may be present. Localized swelling and erythema may also be noted. (4,5) Chronic open wounds are also sometimes present. Wound or draining sinus tracts may sometimes be noted. When present in adjacent areas, enlarging masses may cause nerve compression with resulting sensory or motor deficits. (1,6) Pain and erythema frequently accompany the enlarging mass. (1,3,6)

Differential diagnoses include sarcoidosis, foreign bodies, Crohn's disease, brucellosis, fungal infection, and M tuberculosis infection. (7) The patient's history should prompt suspicion for atypical mycobacterial infections. Biopsy and culture is the only way to make a definitive diagnosis. (8) Biopsies taken from nonulcerated areas adjacent to cutaneous lesions (if present) or excised specimens from surgical debridement are submitted for diagnostic laboratory tests and histologic examination. (8)

Mycobacterium kansasii and its subgroups are classified as group I atypical mycobacteria. They grow best at or around 32[degrees]C. Higher temperatures (34[degrees]C and higher) do not allow incubation of the bacillus, partially explaining their propensity to localization in skin and joints (lower temperatures) and rarity of systemic involvement. (9,10) Known sources of M kansasii and subgroups include contaminated swimming pools, (11,12) fishing tanks, (13,14) piers, boats, brackish water, and seawater, (15-17) fish bites or puncture injuries, (18-21) and even laboratory accidents. (22)

Atypical mycobacteria can be demonstrated with some difficulty at times with staining for acid-fast bacilli. (6) The absence of acid-fast bacteria on staining does not rule out M kansasii or various subgroups, and frequently the organisms can be identified only in culture. (7,23) Cultures on Lowenstein-Jensen media at 28[degrees] to 32[degrees]C are required for at least 2 to 3 weeks and sometimes for longer periods of time. (7,8) The acid-fast bacterium reveals itself as a long, slender, curved or beaded organism on Ziehl-Neelson staining. It forms cream-colored colonies that turn yellow on exposure to light, hence the term photochromogens or group I atypical mycobacteria according to Runyon's scheme. (24)

Mycobacterium kansasii is relatively drug-resistant on in vitro sensitivity studies. These studies are often misleading as a pattern of drug resistance, since clinical application of these drugs reveals in vivo susceptibility and excellent clinical results. (1,4) Mycobacterium kansasii is usually susceptible to streptomycin, rifampin, ethambutol, erythromycin, cycloserine, aminosalicylic acid, and isoniazid. (1-4) The duration of treatment is uncertain, (1-6) but recommended time schemes are 6 to 12 months. Duration of the chemotherapy is related to complete resolution of the lesions. (1-6) There is no consensus on chemotherapy regimen, but all the aforementioned drugs have been proven effective. These agents, though effective, have significant side effects that are well documented. Ethambutol is known to cause ocular toxicity. Rifampin causes rashes, abdominal distress, jaundice, liver dysfunction, tinnitus and vertigo, and flu-like immunologic reactions. Therefore, these patients need to be closely monitore d for complications when using these agents as primary or adjuvant therapy.

Surgical intervention is usually indicated when conservative treatment has failed. Unsuccessful conservative treatment is likely if there is persistent pain or a discharging sinus. A history of previous locally injected steroids also tends to make it more likely that surgical intervention will be necessary. (1,14) Symptoms of a mass effect such as diminished wrist and finger range of motion or nerve entrapment are indications for early surgical excision. (1) Early aggressive operative debridement may obviate the need for arthrodesis or amputation because of the aggressive nature of the organism and failure of conservative therapy to eradicate the infection. (8)

Dual infections involving atypical mycobacteria and M tuberculosis are rare. (25) No predisposing risk factor is apparent for dual infections because of the different modes of transmission and infection vectors, with the possible exception of immune compromise leading to increased susceptibility. These dual infections are most commonly reported to be due to concomitantly cultured M avium-intracellulare and M tuberculosis. Dual infection with an atypical mycobacterium and M tuberculosis has previously been reported only in lymphadenopathy specimens. (25)

Our patient had an enlarging distal volar forearm mass and symptoms of carpal tunnel syndrome. Treatment before referral had been observation and a wrist splint. After exploration of the median nerve, decompression, and synovectomy (Figs 1, 2, and 3), oral rifampin therapy was begun. Tissue pathology revealed the absence of granulomas, and stains for acid-fast bacilli were negative. Histology showed fibrosis, fibrin deposition, and acute inflammation with chronic synovitis. Cultures at 49 days showed M kansasii. Pulmonary tuberculosis was subsequently diagnosed, and the patient was treated with ethambutol and isoniazid. After 9 months, follow-up showed absence of median nerve compression symptoms and fully regained function (Figs 4 and 5). Dual infection with atypical mycobacterium, and M tuberculosis is rare and may be resistant to standard antituberculous drugs. (25)

CONCLUSION

Mycobacterium kansasii is an uncommon but persistent infection that requires a high index of suspicion to be diagnosed. The lesion must be biopsied and cultured immediately, with the understanding that a negative culture does not rule out an infection. It must be aggressively treated with usually months of oral antituberculous and antimicrobial agents if there is not persistent pain, a draining sinus, or history of steroid use. If conservative management fails or if the patient becomes symptomatic, early exploration, excision, and debridement are indicated. Patients with atypical bacterial infections may also have a concomitant M tuberculosis infection and should be appropriately evaluated.

References

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(3.) Sanger JR, Stampfl DA, Franson TR Recurrent granulomatous synovitis due to Mycobacterium kansasii in renal transplant recipient. J Hand Surg Am 1987; 12:436-441

(4.) Gunther SF, Ellioptt RC: Mycobacterium kansasii infection in the deep structures of the hand. J Bone Joint Surg Am 1976; 58:140-142

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(6.) Kozin SH, Bishop AT: Atypical Mycobacterium infections of the upper extremity. J Hand Surg Am 1994; 19:480-487

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(10.) Cortez LM: Mycobacterium marinum infections of the hand. J Bone Joint Surg Am 1973; 55:363-370

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(12.) Enabaek HC, Thormann J, Vergmann B: Aquarium borne Mycobacterium marinum granuloma. Scand J Infect Dis 1980; 12:74-88

(13.) Black H, Rush-Muro FM, Woods G: Mycobacterium infections acquired from tropical fish tanks. Aust J Dermatol 1971; 12:155-164

(14.) Chow SP, Stroebel AB, Lau JHF, et al: Mycobacterium marinum infection of the hand involving bony structures. J Hand Surg Br 1983; 8:568-572

(15.) Dickey RF: Sporotrichoid mycobacteriosis caused by Mycobacterium marinum (balnei). Arch Dermatol 1968; 98:385-391

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RELATED ARTICLE: KEY POINTS

* Mycobacterium kansasii is an uncommon infection of the hand.

* Dual infections of M kansasii and Mycobacterium tuberculosis are rare.

* Atypical mycobacterial infections are difficult to diagnose and require special stains and cultures.

* Multidrug treatment is indicated as first-line therapy in atypical mycobacterial hand infections, but surgical intervention is indicated in symptomatic or complicated cases.

From the Institute for Tissue Repair, Regeneration, and Rehabilitation, Department of Veterans Affairs Medical Center, Bay Pines, Fla; and the Department of Surgery, University of South Florida, Tampa.

Reprint requests to Wyatt G. Payne, MD, Bay Pines VA Medical Center, Plastic Surgery Section, Surgical Service (112), 10,000 Bay Pines Blvd, Bay Pines, FL, 33744.