Lupus erythematosus subacute-cutaneous L93.1

Sontheimer, 1979

Independent, photosensitive (photosensitivity is to be expected in about 80% of patients - Black et al. 2002) subgroup of cutaneous lupus erythematosus with relapsing activity and occurrence of disseminated, red, mostly blurred, homogeneously disc-shaped, but also anular, saturated red plaques, which preferentially occur in light-exposed skin areas.

The light-relatedness results from the "macro-pattern", which usually (not always) omits non-UV-exposed skin areas (note: there is not always a temporal relationship between the appearance of the skin changes and the previous UV exposure; this may have taken place months before!)

There is a higher risk of systemic involvement than with the chronic discoid variant(lupus erythematosus chronicus discoides).

In older patients, SCLE can be associated with malignancies (paraneoplastic subacute cutaneous lupus erythematosus), with non-Hodgkin's lymphomas and carcinomas of the solid organs being observed most frequently (Lazar AL 2022).

Exposure to the sun. There is a varying degree of UV sensitivity.

Drugs are assumed to be the trigger in about 25-30% of cases. Possibly due to abnormalities in drug metabolism (polymorphism of hepatic acetyltransferase, slow acetylators) or drugs that have a photosensitizing effect per se. Increased susceptibility in the presence of HLA types B8, DR2, DR3, DQw2, DRw52 appears to be pathogenetically relevant.

Predominantly affects fair-skinned (Caucasian) women; initial manifestation between 30-50 years of age.

Light-exposed areas: face (leaving out the mid-face and periorbicular region rather), upper thorax, arms.

Integument: Acute, chronically active, multiple or numerous, disseminated, sharply or blurredly defined, 0.2-5.0 cm (rarely > 10.0 cm), disc-shaped, anular or gyrated, red or red-brown spots or plaques with a smooth but also crusty surface. Blistering is possible.

Erythema multiforme-like skin lesions are also possible. In these cases, clinical differentiation from Rowell's syndrome is difficult.

Characteristic are (temporarily persistent) hypopigmentation (more rarely also hyperpigmentation) after healing of the lesions.

Extracutaneous manifestations:

• renal (16%)
• hematologic pathology (8%)
• Minor visceral involvement with polyarthritis, serositis (1%)
• cerebrovascular complications are rarer.

The clinical picture of drug-induced SCLE is identical, but usually occurs in the form of a disseminated exanthema.

At 75% higher titre ANA, more rarely anti-DNA antibodies. Particularly characteristic is the detection of anti-SSA/Ro-antibody (about 50% of cases) and anti-SSB/La-antibody. Possibly leukopenia (cytopenia), hypergammaglobulinemia.

Basically as in cutaneous lupus erythematosus, but less marked hyperkeratosis. Atrophic epithelium, orthokeratosis, vacuolar degeneration of basal epithelial cells, civatte-bodies (interface dermatitis). Profuse dermal edema with mucin deposition, dense perivascularly oriented lymphocytic infiltrate.

The diagnosis of subacute cutaneous lupus erythematosus lupus erythematosus is based on the patient's history, clinical presentation, laboratory tests, and skin biopsy specimens.

External glucocorticoids (e.g. Dermatop) are only moderately successful. Light protection is important - both in the UVB and UVA range!

Initial glucocorticoids such as prednisone (e.g. Decortin) 20-40 mg/day p.o., possibly higher doses. Alternatively cloprednol (Syntestan) 10-15 mg/day. Reduce dosage depending on clinic. This treatment approach can bridge an exanthematous acute situation well.

Antimalarials should be the first choice for systemic therapy e.g. chloroquine start with 250 mg/day, after 2-4 weeks reduce to 250 mg every 2nd day).

Thalidomide and lenalidomide, systemic retinoids, dapsone, and methotrexate represent second-line options in selected cases.

Third-line therapeutic options include mycophenolate mofetil and other immunosuppressive drugs.

The monoclonal antibody belimumab, which targets soluble human B-cell activating factor, is a fourth-choice treatment for refractory cases.

Quoad vitam favorable. Chronic course is characteristic.

Skin lesions usually heal completely and without scarring. Hypo- or hyperpimgentations are possible.

More than 50% of patients are positive for more than 4 ARA criteria (see lupus erythematosus, systemic).

About 15% of patients develop internal involvement (arthralgias, nephritis, cardiac involvement, hematologic complications) during the course of their disease and fulfill the criteria of systemic lupus erythematosus.

There are several authors who classify subacute cutaneous lupus erythematosus as a facultative paraneoplastic dermatosis. SCLE patients should undergo thorough cancer screening to rule out an underlying malignancy with a clinically silent evolution (Lazar AL 2022).

The following drugs have been described in connection with the initiation or exacerbation of SCLE: non-steroidal anti-inflammatory drugs (e.g. piroxicam), tetracyclines, antifungals (griseofulvin; terbinafine), antihypertensives (captopril, cilazapril, hydrochlorothiazide), proton pump inhibitors. Also described are: spironolactone, cinnarizine, D-penicillamine, interferon beta, ranitidine, antidiabetics (sulfonylureas), doxorubicin, docetaxel, carboplatin (see below cytostatics, extravasates) and the PD-1 inhibitor tislelizumab.

Drug-induced CLE (DI-CLE) is also classified as a subgroup of CLE (Di-CLE) and usually appears as SCLE. Discoid skin lesions are rarely drug-induced.

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