Fishing-Injury-Related Flexor Tenosynovitis of the Hand: A Case Report and Review

Hand infections occurring after fishing and other marine-related activities may involve uncommon bacteria that are not susceptible to the conventional or empiric antibiotic therapy used to treat soft tissue infections. Therefore appropriate treatment is often delayed and could lead to severe hand damage. An illustrative case of fishing-related injury leading to complicated tenosynovitis and horseshoe abscess caused by Mycobacterium marinum and its treatment course is outlined. Laceration of the skin during boating is fairly common. Because of the rarity of some of the bacteria, referrals to the appropriate specialist including hand surgeons and infectious disease specialists should occur in early stages. M. marinum infections should always be considered in injuries related to seawater and fishing as this may lead to early appropriate treatment and prevent severe damage.


Introduction
An otherwise healthy 65-year-old right-hand-dominant man was referred with numbness in the median nerve distribution and tenosynovitis of the le small �nger and thumb.
e patient recalled a penetrating injury with a barnacle in the �exor crease of his nondominant le-hand small �nger 2 months prior to presentation. e initial laceration healed without any problems. e erythema persisted and the swelling did not resolve, limiting the range of motion in the small �nger at the proximal interphalangeal joint level. He was concerned about a foreign body and went to an emergency room 1 month prior to presentation at our hand surgery service. X-rays at that time demonstrated no evidence of phalangeal fracture, bony involvement, or presence of a foreign body. He was treated empirically with two courses of amoxicillin/clavulanic acid for ten days. His symptoms failed to resolve on this regime and his antibiotic therapy was changed to doxycycline for ten days. He continued to experience swelling and erythema involving the small �nger. Two months aer the initial injury, the patient presented to the ER again. is time with swelling and erythema involving the small �nger and the thumb and a painful wrist �Figures 1, 2, and 3). e pulses were palpable; the capillary re�ll was within normal ranges. His wrist and thumb were also swollen and painful on passive and active ranges of motion. He had no fever and his white blood cell count was 7.3 K/cmm. e magnetic resonance imaging taken in the emergency department demonstrated in�ammation extending around the small �nger �exor tendon proximally to the region of the carpal tunnel and also to the volar aspect of the hand and into the thumb. e �ndings were reminiscent of a horseshoe abscess of the hand. e patient was then admitted, and the horseshoe abscess with associated tenosynovitis was treated with surgical drainage under general anesthesia.
Brunner incisions were used to drain the small �nger; an oblique incision was made for thenar and hypothenar spaces and a carpal tunnel release incision was done. No evidence of pus was revealed; however, a marked clear �uid was evident throughout the hand. ere was marked proliferation of synovial sheaths in the carpal tunnel. Cultures  for aerobic, anaerobic, acid fast bacilli, and fungus were taken along with a synovial sheath biopsy ( Figure 4). e wound was copiously irrigated with saline and an irrigation system consisting of a pediatric feeding tube size number 5 Fr was inserted into the synovial sheath with open-tube drainage. e skin was loosely sutured to allow drainage ( Figure 5). e Infectious Diseases Service was consulted and an empiric therapy was commenced with vancomycin, piperacillin/tazobactam, ethambutol, and Rifampin. M. marinum was strongly suspected due to the chronicity of the hand infection and the history of injury with seawater exposure.
Signi�cant improvement in the in�ammation was observed aer surgery. Erythema and swelling in the wound decreased and the irrigation system was removed on the 3rd day. At the same day, active and passive ranges of motion exercises were started, and the patient demonstrated increased mobility and good response to therapy throughout treatment.
e bacterial smear and culture did not demonstrate or isolate any bacterial pathogen, respectively. e pathology specimen demonstrated granulomatous tenosynovitis with acid fast bacilli ( Figure 6). Two and a half weeks aer his surgical procedure, M. marinum was isolated from mycobacterial tissue cultures (Figure 7). His antibiotic regime was subsequently changed to clarithromycin 500 mg twice daily, as he was adamant about minimizing his medication burden. He continued with clarithromycin as an outpatient. His  horseshoe abscess and tenosynovitis healed without evidence of recurrence aer 3 consecutive months.

Discussion
e course of the disease is insidious in M. marinum tenosynovitis as it is oen misdiagnosed upon initial presentation. Most patients present with atypical symptoms including pain, swelling, and lack of movement. In later stages, tendon thinning and tendon rupture can occur.
Horseshoe abscess is a complication of a �exor tenosynovitis occurring aer progression of the infection following the synovial communication between the radial and ulnar bursae at the wrist level. As is seen in this case, involvement of the small �nger tendon sheath extends to the ulnar bursa. e ulnar bursa communicates with the radial bursa in the wrist level at the potential Parona's space. By this route, the infection extends to the thumb �exor sheath. e horseshoe abscess can be drained by a combination of small �ngerulnar bursae and �exor pollicis radial bursa incisions [1]. e patient also had decreased sensation in the median nerve distribution. Pus in the thumb �exor sheath can also lead to infection in carpal tunnel causing the carpal tunnel syndrome symptoms [1][2][3].  M. marinum is a nontuberculous mycobacteria found in aquatic environments, fresh and seawater, �sh tanks, and nonchlorinated swimming pools. Among the vectors of infection are marine organisms such as fresh or saltwater �sh and shell�sh. e estimated incidence of M. marinum so tissue infection is 0.27 per 100,000 [4]. It typically causes a chronic granulomatous so tissue infection. e incubation period ranges from 2 to 6 weeks. Aer trauma and contact with Mycobacterium marinum, usually a solitary papule appears on the extremity enlarging to a nodule or plaque progressing at times to ulceration-"Swimming pool granuloma. " Rarely involvement of the proximal lymph nodes may progress to scrofuloderma [4,5].
Physician's awareness of Mycobacterium marinum is necessary to treat this slow infection early [6]. Delay in treatment can cause direct extension of the cutaneous infection to the deep structures causing in�ltration of the tendon sheath, bursae, joints, and bones in 29% of reported M. marinum infections [7]. Tenosynovitis is the most common infection involving deeper tissues [5]. e disseminated disease is rare and occurs in immunosuppressive therapy as in transplant recipients and rheumatoid patients [8,9]. e diagnosis is based on the clinicohistological features and response to treatment [6]. Diagnosis involves both biopsy of the involved tissue for histopathological evaluation and culture. Synovial lesions may resemble a rheumatoid disease. e treatment is debridement and pharmacological therapy [1]. Aer debridement, large defects can be le open or vacuum-assisted closure could be used [10]. In our patient, although there was no pus, synovial tissue proliferation and clear �uid was evident through the small �nger and �exor sheath and �exor pollicis longus tendon sheath involving the tendons in the carpal tunnel. Although the disease is indolent, rapid progression of the disease leading to index �nger amputation is also reported [11]. Deep infections can cause signi�cant damage with marked proliferation if in the synovial tissue, erosion of the joints, involvement of the �exor and extensor tendons. Pus may be evident tracking into the forearm or to the potential spaces in hand [12].
M. marinum may be isolated from cultures in two to three weeks. is mycobacterium species grows optimally at lower temperatures of between 28 and 33 ∘ C. It is, therefore, important to notify the microbiology laboratory of the possibility of this species so that cultures are incubated at the appropriate temperature.
Susceptibility testing of M. marinum isolates demonstrates susceptibility to rifampin, rifabutin, ethambutol, clarithromycin and sulfonamides, and trimethoprim/sulfamethoxazole. It may demonstrate full or intermediate susceptibility to doxycycline and minocycline and intermediate susceptibility to streptomycin. It is resistant to isoniazid and pyrazinamide [13,14]. e natural course for M. marinum infections is slow spontaneous resolution in 1-6 years. e aim of the treatment of super�cial lesions is to prevent the rare progression to deep infection [12]. e localized or super�cial disease may be treated with a single agent by some specialists.
Good outcomes have been reported for combinations with clarithromycin and ethambutol or ethambutol and rifampin. A rifampin-based regime is recommended for cases with osteomyelitis [14]. ere have been no published randomized controlled trials comparing the various treatment regimes for so tissue infection caused by M. marinum. For super�cial infections, the antibiotic therapy is given for 6 weeks to 6 months. e optimal treatment period is determined by clinical response [9]. For deep infections, the duration of the therapy is for 6 to 18 months [12]. e patient should be controlled for reactivation of the disease aer the discontinuation of the medication. e American oracic Society/Infectious Disease Society of America recommends treatment with two active agents for one to two months aer resolution of lesions, approximately three to four months of total therapy [14].
Although rare, hand infections caused by injuries related to �shing can result in serious complications. Waterborne infections can be acutely fulminant, such as necrotizing fasciitis that results from "Vibrio" infections or chronic in nature that include atypical "mycobacteria. " Chronic infections are oen underdiagnosed and there is oen a delay in treatment. M. marinum infection should be considered early when patients present with a �shing-related injury such as a cut with a hook, exposure to �sh, and small lacerations with shells that are problematic to heal. Early recognition and treatment of �shing-related hand infections could prevent severe damage to vital structures in the hand.

�on�ict of �nterests
All named authors hereby declare that they have no con�ict of interests to disclose.
Funding is research received no speci�c grant from any funding agency in the public, commercial, or not-for-pro�t sectors.