Sporotrichoid Cutaneous Infection Caused by Mycobacterium Marinum

Mycobacterium marinum commonly produce lymphocutaneous infections.1 Failure to suspect mycobacterial disease can delay diagnosis and initiation of adequate therapy. Case report. A healthy 3-year-old Caucasian girl was brought for consultation because of a nodular lesion on the back of her right hand that had appeared 3 months previously. The patient, whose parents owned a tropical fish tank, had been treated with a course of oral amoxicillin but had shown no improvement. On physical examination a non-tender, violaceous, crusted papulonodular lesion was found on the back of her right hand. There were two additional, noncontiguous nodules on the back of the same hand and the right elbow, mimicking cutaneous sporotrichosis. Simultaneously, there was an inflammatory, slightly erythematous, linear area between the initial lesion and the subcutaneous nodule located on the back of the right hand (Fig. 1). All routine laboratory studies were normal, as was the radiography of the chest and hand. Mantoux skin testing revealed 10 mm of induration. Fungal and bacteriologic cultures were negative. Histologic studies disclosed a granulomatous inflammatory infiltrate with scattered giant cells within the dermis, without caseation. Ziehl-Nielssen and rhodamine-auramine stains were negative. Culture performed in Löwenstein-Jensen medium incubated at 30°C yielded M. marinum. This result was confirmed by a reference laboratory (Instituto Carlos III, Madrid, Spain) and treatment with rifampin and ethambutol was started. Antibiotic susceptibility tests were not performed. All lesions disappeared in 2 months, although therapy was continued for a further 3 months.Fig. 1: Subcutaneous lesions and lymphangitis on the back of the right hand following the regional lymphatic pathway from the affected finger.Comment.M. marinum was first described in 1926 by Aronson2 and was found to be responsible for infectious cutaneous disease in 1954 by Linell and Norden,3 who preferred the name Mycobacterium balnei (Latin for "from the bath"). In 1962 Swift and Cohen4 reported the first case of M. marinum infection acquired from a tropical fish tank in an adult patient with chronic eczema of the hand. M. marinum is an acid-fast, photochromogenic mycobacterium belonging to the Runyon Group I. It grows at 30-32°C. In humans it is responsible for the cutaneous lesions known as "swimming pool granulomas" or "fish tank granulomas," which appear after infection of the skin with contaminated water at previous points of trauma. Consequently the most common locations are the exposed areas of the body such as the extremities,5-7 although some cases of facial involvement have also been described in children.8, 9 To our knowledge the youngest child with cutaneous, nondisseminated infection by M. marinum reported to date was a 14-month-old.5 Most children have a history of exposure to water while swimming,7 feeding fish or playing with aquaria.6, 9 The incubation period after inoculation is relatively long, ranging from 2 to 6 weeks.10 The classic picture consists of a violaceous to reddish, painless papule developing at the inoculation site, which later becomes verrucose or ulcerated and crusty. In 20% of cases secondary nodular lesions are found along the regional lymphatic vessels, resembling those seen in cutaneous sporotrichosis.11 On histologic grounds the lesions show a granulomatous inflammatory infiltrate without caseation, with occasional Langhans giant cells.12 Acid-fast smears are negative in up to 90% of cases, and according to the report of Lotti and Hautmann13 bacilli are especially rare in granulomatous infiltrates but more numerous in suppurative lesions. Culture is positive in most cases, although it must be performed in Löwenstein-Jensen medium incubated at 30-32°C for 2 weeks.11 Tuberculin skin tests are usually positive because of cross-reaction with Mycobacterium tuberculosis. Unlike other nontuberculous mycobacteria, photochromogens may induce a skin induration as large as those found in M. tuberculosis lesions, and hence this test is not helpful in distinguishing M. marinum from M. tuberculosis.14 Recently the diagnosis of M. marinum by PCR-based DNA analysis has been proposed.6, 15 Epidemiologic investigation is essential to achieve an accurate diagnosis and should address such aspects as recent travel history, hobbies, recreational activities, the existence of household pets, eating habits, traumas, etc., to exclude other causes of cutaneous sporotrichoid infection (Table 1).1, 16 Nodular lymphangitis develops most commonly after cutaneous inoculation with Sporothrix schenckii, Nocardia brasiliensis, Leishmania braziliensis and Francisella tularensis. Sporotrichosis and leishmaniasis can have longer incubation periods than do the other causes of nodular lymphangitis. A painful ulcer at the site of the initial lesion suggests tularemia; severe purulent drainage often accompanies infections with Francisella and Nocardia species. Ulcerated or suppurating lymphangitic nodules occur commonly with Nocardia infections.1TABLE 1: Characteristics of different sporotrichoid cutaneous infections Currently there is no proven best treatment for M. marinum infection. Traditionally the combination of rifampin (300 mg/day) and ethambutol (600 mg/day) has been used, but therapy with minocycline, doxycycline,9 trimethoprim-sulfamethoxazole17 and levofloxacin18 has also been used, either alone or in association, with good results. Clarithromycin is also active against M. marinum19 and has been shown to be effective in children, in association with rifampin.6, 8, 9 Response to treatment is slow and therapy should be continued for several months. Finally the surgical approach is also possible, especially in isolated lesions. However, controversy exists as to whether surgery might enhance the extension of M. marinum to deeper structures such as joints and tendons.11 Angela Hernández-Martín, M.D. Eduardo Fonseca, M.D. A. González, M.D. Carmen Peña, M.D. Jesús del Pozo, M.D. Jesús García-Silva, M.D. Fundación Hospital Verín; Verín, Ourense, Spain (AHM)