Acute courses of CLE clinically present with plane redness in sun-exposed skin areas, particularly in the face, décolleté, and extensor sides of the arms. The most characteristic clinical sign is the butterfly rash, a symmetric, circumscribed, aliform erythema on both cheeks. This CLE subset shows a close association to SLE in younger female patients and may be accompanied by fever, myalgia, fatigue, and involvement of internal organ systems. In the peripheral blood, often high-titer antinuclear antibodies with SLE-typical specificity (e.g., anti-dsDNA, anti-Sm) are detectable. In contrast to the impressive clinical picture, the histological changes may be discrete. The slides show a mild edema with only minor mucin deposits. However, some neutrophils may accompany the dermal and junctional inflammatory infiltrate. These are rarely found in other CLE subsets and may be indicative for ACLE [5].

The BLE is a very rare subset of ACLE which presents clinically with confluating small vesicles on erythematous skin in sun-exposed skin areas. Circulating anti-collagen VII antibodies, which target structures in the basement membrane, are typically found in the peripheral blood of the patients affected. Histologically, skin lesions show a subepidermal blister (effect of the anti-collagen VII antibodies) and a neutrophil-rich inflammatory infiltrate (close association to ACLE/SLE).

The SCLE presents clinically with widespread annular, gyrated, and/or plaque-like erythrosquamous lesions in sun-exposed skin areas including décolleté and extensor sides of the arms, while the face typically is not involved. The majority of SCLE patients are ANA-positive. Among the ANA, anti-SSA/Ro and anti-SSB/La antibodies are the most characteristic antibodies for this CLE subset. These antibodies not only are important diagnostic markers but also have a functional impact, since newborn babies of anti-SSA/Ro-positive mothers have an increased risk to develop SCLE-like skin lesions which diminish with the decline of the maternal postpartal immunoglobulin protection. From a histological point of view, SCLE shows a cell-poor interface dermatitis with vacuolar degeneration of the basal epidermal layer, colloid bodies, immigration of skin-homing lymphocytes, and dermal mucin deposits [6, 7].

LET clinically presents with infiltrated erythematous maculae and plaques without epidermal scaling which primarily appear in sun-exposed skin areas including the face. LET shows a dynamic which is between subacute CLE and chronic CLE and therefore was classified as “intermediate CLE type” in the Düsseldorf classification of CLE [1]. Histologically, the lesions are characterized by an extensive dermal spot-like perivascular and perifollicular inflammatory lymphoid infiltrate without any epidermal component. This inflammation is dominated by CD123-positive plasmacytoid dendritic cells, which form clusters of more than ten cells together. This inflammation is accompanied by strong dermal mucin deposits. Most of the patients are ANA-negative, and SLE-typical organ manifestations are uncommon in LET. Particularly, anti-SSA/Ro and SSB/La, which are frequently found in other photosensitive CLE subsets, are almost completely lacking [8, 9].

The most common CLE subset is the chronic discoid LE (CDLE). It presents clinically with chronic, discoid, scarring, erythrosquamous plaques particularly affecting the capillitium and face. Most manifestations remain localized to one body region, but extensive courses with widespread scarring lesions appear in up to 10 % of the cases. In contrast to the extensive lesional skin damage, CDLE patients have only a minor risk to develop SLE, and the ANA titers are usually low. The most typical clinical sign of CDLE is the so-called tin-tack sign: a painful hyperkeratosis with follicular plugging due to the follicular hyperkeratosis of CDLE. Histologically, the lesions show a dense periadnexal and perivascular lymphoid inflammation, accompanied by a cell-rich interface dermatitis with a broadened basement membrane. Older lesions are characterized by fibrosis, due to the scarring character of this CLE subset [5].

In early stages, patients suffering from LEP show subcutaneous nodules and pad-like indurations of the dermis and subcutis. During the course of the disease, the patients develop lipoatrophy with retractions of the skin. The gluteal region is the predilection site of the disease, but the thighs, upper arms, and the face may also be involved. Histologically, LEP (also called “lupus panniculitis”) shows a lobular panniculitis with several CD8-positive cytotoxic T cells, accompanied by CD123-positive plasmacytoid dendritic cells and lesional expression of type I IFN-regulated cytokines. CLE-typical changes may also be seen in the dermis (e.g., mucin depositions) and at the dermoepidermal junction (interface dermatitis) in individual cases [10–12].