Case Presentation: A 54-year-old Hispanic male with a history of type II diabetes with A1C of 6.7% presented with a nonhealing upper extremity skin lesion. Nine months prior to presentation the patient injured the fourth digit of his left hand after being speared by the back fin of a fish while fishing in Galveston. The patient experienced swelling and pain at the site, along with ulceration and verrucous lesions. Also, a similar appearing lesion developed on his left elbow. Despite a course of vancomycin and clindamycin for empiric treatment of cellulitis 5 months after the injury, he saw no improvement. Punch biopsy prior to initiation of antibiotics was unrevealing. At the time of presentation, the patient complained of pain and swelling of the third and fourth digits of his left hand, causing him difficulty in flexion of his fingers. He was afebrile with elevated ESR and CRP but without leukocytosis. MRI of the hand revealed possible osteomyelitis of the distal fourth finger and patient underwent deep tissue biopsy, with performance of MTB PCR and acid-fast bacilli (AFB) stain and culture grown at 30 °C given concern for atypical mycobacterium. Stain was positive for AFB, and rifampin and isoniazid were started for presumed mycobacterium marinum. Culture and PCR were positive for mycobacterium tuberculosis and therapy was expanded to rifampin, isoniazid, pyrazinamide, ethambutol, with improvement in his lesions over the next month.
Discussion: Cutaneous tuberculosis accounts for 1-2% of all tuberculosis cases, with those who are immunocompromised and from developing countries most likely to develop cutaneous TB. Regarding our immunocompetent patient, while diabetes has been shown to be a risk factor for the development of pulmonary TB, there is a paucity of epidemiologic data regarding the coexistence of diabetes and cutaneous TB. Additionally, atypical mycobacteria are more likely to cause skin infection than M. tuberculosis.
This case highlights the importance of obtaining a thorough history and examination when evaluating a chronic nonhealing wound, as well as considering a mycobacterial etiology in those who are immunocompetent. In cases where there is suspicion for atypical infection, deep tissue biopsy with AFB culture and PCR of the specimen should be performed for diagnosis, keeping in mind the specific growth requirements for slowly growing mycobacteria. For suspected infectious wounds, biopsies should be obtained in the center of the lesion for the best yield.
Conclusions: Chronic wounds are a common healthcare problem with multiple potential etiologies. Timely biopsy of nonhealing wounds is important, with appropriate stains sent for potential causative organisms, including mycobacteria.