The Brief Case: Delayed Diagnosis of Cutaneous Mycobacterial Infection in Rural Mississippi

CASE An 85-year-old Caucasian man with no significant past medical history presented to an outside dermatology clinic with a 6-month history of rash on his hands and feet. The patient worked as a farmer for 30 years in rural Mississippi and retired 30 years prior. He denied any known trauma or penetrating injury, exotic exposures, or significant travel except to South Korea 60 years ago. Skin biopsy was performed on the right dorsal hand and revealed granulomatous inflammation on hematoxylin and eosin stain (HE stain). Acid-fast bacillus (AFB) stain was positive for numerous bacilli on both histopathology and on tissue submitted to the clinical microbiology laboratory. However, mycobacterial cultures demonstrated no growth after 8 weeks of incubation. The skin lesions continued to progress despite 6 weeks of clarithromycin, which was stopped due to diarrhea, followed by 4 weeks of ciprofloxacin and minocycline. The lesions were associated with significant pain and swelling, prompting him to present to our medical center for further evaluation. On physical examination, the patient was in mild distress but afebrile, alert, and oriented. Skin examination revealed tender, erythematous plaques and diffuse edema on bilateral hands extending to the elbows (Fig. 1A) and on feet extending below the knees (Fig. 1B). C-reactive protein was 16.3 mg/dL (reference range, 0 to 0.50 mg/dL), the erythrocyte sedimentation rate was 54 mm/h (reference range, 0 to 29 mm/h), and the white blood cell count was 5.6 cells/mL (reference range, 4.0 to 10.0 cells/mL). A tuberculosis interferon gamma release assay was negative. A computed tomography scan of the chest, abdomen, and pelvis did not show any abnormalities. A repeat skin biopsy was performed on the right forearm. Histopathology showed extensive granulomatous inflammation on HE stain (Fig. 2A), with Ziehl-Neelsen stain showing clusters of acid-fast bacilli throughout the dermis (Fig. 2B). There was no neural tissue involvement. In the microbiology laboratory, the specimen was positive for AFB by auramine-rhodamine fluorochrome stain, and a subsequent Kinyoun stain demonstrated.9 AFB/high-power field (Fig. 2C and D). Biopsy material was inoculated onto various media, including broth (Middlebrook 7H9; MGIT) and a Lowenstein-Jensen (LJ) slant, both incubated at 37°C; additional LJ and chocolate slants were incubated at 30°C to optimize growth of some fastidious cutaneous mycobacteria. Differentials included Mycobacterium abscessus,Mycobacterium chelonae,Mycobacterium haemophilum, andMycobacteriummarinum as potential mycobacteria responsible for causing cutaneous infection. Curiously, no growth was seen on mycobacterial cultures after 6 weeks. Since the skin biopsy specimen showed abundant amount of organism, the formalin-fixed paraffin-embedded tissue block was sent for molecular identification to a reference laboratory (Molecular Microbiology Laboratory, Department of Laboratory Medicine and Pathology, University of Editor Carey-Ann D. Burnham, Pattern Bioscience Copyright © 2022 American Society for Microbiology. All Rights Reserved. Address correspondence to Tulip A. Jhaveri, tjhaveri@umc.edu, or Samantha Williams, swilliams25@umc.edu. The authors declare no conflict of interest. For answers to the self-assessment questions and take-home points, see https://doi.org/10 .1128/JCM.00308-22 in this issue. Published 21 December 2022