Red and Orange Colors as Dermoscopic Clues for Fish-Tank Granuloma

Dermoscopy in Mycobacterium marinum infection and its correlation with clinical and histopathological features: a prospective observational study

BACKGROUND

Mycobacterium marinum is a nontuberculous mycobacterium and a conditional pathogen to humans, which can be inoculated directly and cause chronic skin granulomas. Dermoscopy has been applied to other granulomatous skin diseases, but not to M. marinum infection.

AIM

To explore the dermoscopic features of M. marinum infection, and its correlation with clinical and histopathological features.

METHODS

In total, 27 lesions from 27 patients (19 women, 8 men, age range 28-71 years) diagnosed with M. marinum infection were identified by clinical examination, histopathological results, PCR sequencing and mycobacterial culture in the dermatology outpatient department of our hospital from March 2020 to February 2022. The dermoscopy images and pathological characteristics were analysed.

RESULTS

Lesions were located on the hands, forearms and upper arms. The following dermoscopic features were observed: yellowish-orange structureless areas (85·2%), white striped structures (59·3%), follicular plugs (29·6%), yellowish oval clods (14·8%) and reddish or pinkish areas (14·8%). Vessel structures were visible in all cases: long hairpin vessels (81·5%), corkscrew vessels (25·9%), comma-shaped vessels (22·2%) and linear vessels (22·2%).

CONCLUSION

Yellowish-orange structureless areas, white striped structures and long hairpin vessels are the most common dermoscopic features of M. marinum infection. Thus, dermoscopy could be used as a noninvasive auxiliary diagnostic method to provide a diagnostic basis for this disease.

Dermatoscopy of Cutaneous Granulomatous Disorders

Cutaneous granulomatous disorders represent diseases with underlying granulomas on histology and are broadly divided into infectious and noninfectious disorders. Although histology is sine qua non in diagnosis of granulomatous disorders, lately dermoscopy has come up as a useful tool assisting in diagnosis of granulomatous disorder. Dermoscopy of granulomatous disorder is characterized by localized or diffuse, structureless yellowish-orange areas, along with vessels. Dermoscopic features of granulomatous disorders can be overlapping among various disorders, but detailed accurate assessment of various findings and their pattern may be useful in differentiating among them. In addition to this, peculiar dermatoscopic findings seen can also prove useful in distinguishing between various disorders. Hereby, we discuss dermatoscopic findings of various granulomatous disorders.