Dermoscopy of leprosy

What is leprosy?

Leprosy is a chronic granulomatous disorder of the skin and nerves usually associated with Mycobacterium leprae infection.

What are the clinical features of leprosy?

Leprosy presents as a spectrum of disease ranging from multibacillary to paucibacillary forms. The cardinal clinical features of leprosy are hypopigmented anaesthetic patches on the skin and thickened, tender peripheral nerves.

What are the dermoscopic features of leprosy?

Dermoscopic patterns in leprosy vary with the skin site/location, part of the lesion examined, and the type of lesion eg, flat versus raised.

General dermoscopy features of leprosy

• Focal white areas
• Distorted pigment network
• Reduced density of white dots indicating eccrine and follicular openings
• Hair changes — circle hairs, short or broken hairs, V-like hairs, decreased hair density
• Widened skin cleavage lines
• Occasional scale only seen in infiltrated lesions
• Vascular changes — short, linear, dotted, and branching blood vessels in granulomatous and facial lesions; not seen in extra-facial flat hypopigmented lesions
• Yellow and/or yellow-brown globules — in granulomatous facial lesions and infiltrated extra-facial lesions.

Specific dermoscopy features of leprosy

Tuberculoid leprosy

Yellow-orange and brown-orange globules with linear and branching blood vessels which may be poorly focused. Vessels are very difficult to appreciate in flat hypopigmented extra-facial lesions.

Well-defined erythematous plaque on the cheek in skin of colour 

 

Borderline tuberculoid leprosy

Focal white areas and distorted pigment network with white structureless areas. Yellow-orange and/or brown-yellow globular structures with linear vessels are seen in facial lesions and raised extra-facial lesions.

 

 

 

Borderline-borderline leprosy

Focal white areas, distorted pigment network, ill-defined focal red areas with decreased white dots of eccrine and follicular openings. It is difficult to appreciate brown-yellow globules in extra-facial sites in dark skin. A pinkish background can be observed.

Red lesions of variable size. Characteristic 'Swiss cheese' appearance (black arrows) 

 

Borderline lepromatous leprosy

Distorted pigment network with reduction in white dots of eccrine and follicular openings. Focal white areas with white chrysalis strands are usually seen. Brown-yellow globules are not easily appreciated. White rosettes have been described in facial lesions and are non-specific, being seen in many other conditions.

Asymmetrical distribution of erythematous infiltrated plaques in skin of colour 

 

Lepromatous leprosy

Distorted pigment network with chrysalis strands and prominent linear and branching vessels are seen in nodular lesions. Vascular elements are not obvious in patches. Globules are difficult to find.

 

Leonine facies with loss of eyebrows and infiltrated facial skin 

 

Histoid leprosy

White structureless areas with linear and branching vessels running towards the centre of the lesion, so-called crown vessels. White chrysalis strands and peripheral brownish pigment are typically seen.

Dome-shaped papules and nodules in skin of colour 

 

Pure neural leprosy

Prominent skin lines with white scale and changes in the pigment network.

 

 

What is the dermoscopic differential diagnosis for leprosy?

• Pityriasis versicolor dermoscopy: diffuse white structureless areas with faint pigment network and fine white scale. No changes seen in hair and vascular elements.
• Hypopigmented mycosis fungoides dermoscopy: short linear spermatozoan-like vessels, focal white scales, brown-yellow structures, and a whitish background.
• Lupus vulgaris dermoscopy: brown-yellow globules, linear and branching vessels, and white chrysalis strands. Follicular plugs and prominent white scale are conspicuous in lupus vulgaris but not in leprosy.
• Sarcoidosis dermoscopy: well-focused linear vessels with orange-yellow globules, scale, and follicular plugs.

What is the histological explanation of the dermoscopic features of leprosy?

Focal white areas and broken pigment networks correspond with decreased basal layer melanin and flattening of rete ridges respectively. The decrease in white dots is due to a reduced number of follicular and eccrine structures. Granulomas are seen particularly on skin biopsy of the tuberculoid forms of leprosy, and are responsible for the brown-yellow globules. Linear and branching vessels are dilated capillaries. White chrysalis strands correlate with dermal collagen [see Leprosy pathology].