Granulomatous and Autoimmune Inflammatory Dermoscopy

01Granuloma annulare. The pattern is highly variable. Vessels can be dotted, short linear, or linear-arborizing, on a background that ranges from red, white, red-white, to yellow-white. Pigment structures appear in some lesions. There is no single repetitive pattern, but GA rarely shows the prominent linear-arborizing network of NL or the dense orange-yellow globules of sarcoidosis. The most consistently described background is red-orange structureless with white reticular structures (white pseudonetwork). Annular configuration with peripheral erythema and central clearing is the clinical anchor.

02Sarcoidosis (cutaneous) and lupus vulgaris. Both show orange-yellow translucent globules or structureless areas (apple jelly on diascopy, also called yellow-orange blot), combined with linear, branching, or arborizing vessels. The orange-yellow color reflects dermal granulomas seen through epidermis. Differentiating sarcoid from LV (cutaneous TB) on dermoscopy alone is unreliable; clinical context (mycobacterial exposure, systemic disease) drives the call. The combination of orange-yellow plus linear vessels is the key signal that says granulomatous.

03Necrobiosis lipoidica. The repetitive pattern is a prominent network of linear arborizing vessels on a yellow-orange background, often with central yellow-white structureless zones (necrobiosis), surface ulceration, and yellow crusts. NL has the most striking vascular network of any granulomatous dermatosis, and the prominence of the network is what separates it from sarcoid or GA in the same yellow-orange family.

04Discoid lupus erythematosus. Stage matters. Early DLE: perifollicular whitish halo, follicular keratin plugs (prominent yellow plugs filling follicular openings), white scales, dilated dotted and coiled vessels. Late or burnt-out DLE: pigmentation structures (brown or grey-brown dots and globules in a peppered pattern), linear telangiectasias, and white structureless scarring areas. Follicular red dots, described by Tosti in scalp DLE, are bright red follicular openings indicating active disease and predicting response to systemic therapy. The combination of perifollicular plugs plus telangiectasias plus scaling on the face is highly specific for DLE and separates it from rosacea, LV, and lupus pernio.

05Lupus tumidus. Less well characterized dermoscopically. Reports describe a salmon-pink to red structureless background with sparse dotted vessels, no follicular plugging (in contrast to DLE), and absent scale. The lack of follicular involvement is the distinguishing feature against DLE.

06Dermatomyositis (Gottron papules and sign). Gottron papules over MCP and PIP joints show polymorphous vessels (dotted, linear, branching) on a violaceous to red background, often with fine scale. Periungual telangiectasias and dilated capillary loops with capillary dropout are seen on nailfold capillaroscopy and are highly suggestive of dermatomyositis or scleroderma. Dilated, tortuous, sometimes hemorrhagic capillaries with adjacent avascular zones are the nailfold pattern.

07Lichen sclerosus. White-yellow structureless areas dominate, in genital and extragenital sites. Genital LS adds linear vessels and an erythematous halo around early plaques. Extragenital LS often shows comedo-like openings (keratotic plugs filling dilated follicular ostia, the hallmark for some authors) and peripheral pigmentation. Bullous and erosive variants add red structureless or hemorrhagic zones. The combination of white-yellow plus comedo-like in a vulvar or anal location has high specificity for LS in suspected cases.

08Morphea. Fibrotic white beams (intersecting white-yellow lines, correlating with dermal sclerosis) plus linear vessels are the signature. Active morphea adds an erythematous to violaceous lilac ring at the periphery (the bedside lilac ring confirmed dermoscopically). Late or burnt-out morphea shows mostly white-yellow structureless areas with sparse linear vessels. LS and morphea overlap clinically and dermoscopically; the LS feature of comedo-like openings, the morphea feature of fibrotic beams, separate the two in the Shim 2012 study.