4. Atypical Mycobacterial Skin Infections
This fourth chapter in the section on sports-related skin infections discusses atypical mycobacterial infections in the athlete, specifically Mycobacterium marinum. This infection is unusual but has occurred in epidemic proportions.
A swimmer’s skin is ideal for infection with atypical mycobacteria. First, supersaturation of the stratum corneum (the first layer of protection of the skin) as a result of water immersion permits easy passage of microorganisms through the epidermis. Second, swimmers experience abrasions and cuts from the pool deck, diving boards, and pool walls. These breaks in the epidermis allow additional entrance of atypical mycobacteria into the deeper layers of the skin.
Swimming Pool Granuloma Epidemiology
Mycobacterium marinum, an acid-fast atypical mycobacterium, causes swimming pool granuloma. In rare cases, Mycobacterium scrofulaceum is the cause (Sowers, 1972). The organism typically lives in fresh water or seawater. Affected athletes include boaters, jet skiers, lifeguards, sailors, swimmers, snorkelers, scuba divers, high divers, surfers, rafters, wind surfers, water skiers, and water polo players. After injury to the skin of the aquatic athlete, the organism gains entry into the dermis. Several epidemics of swimming pool granuloma have occurred around the world.
Eighty people (73 children) in England developed M. marinum infection from one pool. Investigators were able to culture the organism from cracks in the pool tile (Galbraith, 1980). One pool in Colorado yielded 290 cases of M. marinum.
The pool had very rough surfaces, and inoculating traumas occurred to most of the swimmers while they were getting in and out of the pool (Philpott et al., 1963).
In Spain a retrospective review of an 8-year period detected 45 cases of M. marinum infection. Eighteen percent of the infections were related to swimming pools (the majority was related to fish tanks). Eighty percent of all patients had a history of local trauma (Casal et al., 2001). Three fourths of all M. marinum infections occur in individuals younger than 30 years.
Clinical Presentation
An erythematous papule occurs at the site of skin injury. After 1 to 2 months, the papule evolves into a verrucous nodule that may ulcerate (Figure 4-1).
During epidemics, the most common locations have been the elbow (85% in many studies) and the hand (82% in some studies). The organism may migrate along the lymphatics and cause multiple linear nodules. Low-grade fevers and extension to the lungs may occur. Cutaneous complications include scarring and pigmentary changes.
Diagnosis
Biopsy reveals a granulomatous infiltrate in the mid-dermis. Cultures grow the organism in 1 to 2 weeks, most optimally at 32°C. Eighty percent of affected individuals have a positive Tb test. The differential diagnosis includes sporotri- chosis (which also produces a pattern of lymphatic spread of red nodules), furun- culosis, gout, leishmaniasis, sarcoidosis, and verruca vulgaris.
Verrucous squamous cell carcinoma mimics swimming pool granuloma and must be considered. This delay in diagnosis occurred in a 37-year-old scuba diver who was incorrectly diagnosed with an infectious process after receiving an injury from a coral formation (Sinnott et al., 1988).
82 Sports Dermatology
Figure 4-1. Well-defined, brown to red, minimally scaling, somewhat lobulated nodule typical of swimming pool granuloma located on an extremity.
Treatment
Warm-water soaks should be applied for 5 to 10 minutes three or four times per day. Typical useful oral antibiotic regimens include minocycline 100 mg twice per day or clarithromycin 500 mg twice per day for at least 6 weeks (most require 2– 4 four months for total healing). Others have used rifampin 600 mg per day in conjunction with ethambutol 15 mg/kg per day (Fisher, 1988). Doxy- cycline, tetracycline, ciprofloxacin, and trimethoprim-sulfamethoxazole are other options (Johnston and Izumi, 1987). In a large retrospective study, 99% of M. marinum infections cleared within 2 to 4 months. Surgical excision also has been suggested. Many believe that 80% of lesions will resolve spontaneously within 3 years.
Prevention
Chlorine has little influence on M. marinum.
Bibliography
Casal M, del Mar Casal M. Multicenter study of incidence of Mycobacterium marinum in humans in Spain. Int J Tuberc Lung Dis 2001;5:197–199.
Fisher AA. Swimming pool granulomas due to Mycobacterium marinum: an occupational hazard of lifeguards. Cutis 1988;41:397–398.
Galbraith NS. Infections associated with swimming pools. Environ Health 1980;Feb:31–33.
Johnston JM, Izumi AK. Cutaneous Mycobacterium marinum infection. Clin Dermatol 1987;5:68–75.
Philpott JA, Woodburne AR, Philpott OS, et al. Swimming pool granuloma. Arch Dermatol 1963;83:158–162.
Sinnott JT, Trout T, Berger L. The swimming-pool granuloma that wouldn’t heal. Hosp Pract 1988;23:82–84.
Sowers WF. Swimming pool granuloma due to Mycobacterium scrofulaceum. Arch Dermatol 1972;105:760–761.
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