Cutaneous lupus erythematosus (discoid and subacute)

Systemic lupus erythematosus is a chronic multisystem autoimmune disease in which antinuclear and other autoantibodies drive immune-complex deposition and organ injury across skin, joints, kidneys, blood, serosa, and the nervous system. Diagnosis rests on a positive antinuclear antibody plus weighted 2019 EULAR/ACR criteria totaling 10 or more points. Hydroxychloroquine is lifelong first-line therapy for nearly every patient, with glucocorticoids and steroid-sparing immunosuppression added for moderate to severe or organ-threatening disease.

Drug-induced lupus is a milder, reversible lupus-like syndrome triggered by an offending medication, marked by transient antinuclear and antihistone antibodies with sparing of the kidney and central nervous system. Management is stopping the culprit drug, with an NSAID or a short low-dose glucocorticoid course for residual arthritis, fever, or serositis.

Photosensitizing drug reactions are drug-induced skin eruptions confined to sun-exposed areas, occurring as phototoxic reactions (common, dose-dependent, an exaggerated sunburn from UVA-absorbing drugs) or photoallergic reactions (uncommon, a delayed eczematous type IV response). Diagnosis is clinical from the photodistribution and drug history, and management is stopping the culprit, photoprotection, and topical corticosteroids.

Rosacea is a chronic inflammatory facial skin disorder with recurrent flushing that produces persistent central-face erythema, telangiectasias, and papulopustules without comedones, triggered by heat, sun, alcohol, and spicy food. Diagnosis is clinical based on subtype; treatment is matched to subtype, with topical metronidazole, azelaic acid, or ivermectin and oral doxycycline for papulopustular disease, laser therapy for telangiectasias, and laser or surgery for rhinophyma.

Dermatomyositis is a complement-mediated inflammatory myopathy causing symmetric proximal weakness with pathognomonic skin findings, heliotrope rash and Gottron papules, that separate it from polymyositis. It carries a 3- to 12-fold increased malignancy risk and a distinct interstitial lung disease burden that drive workup and therapy. First-line treatment is high-dose prednisone with an early steroid-sparing agent.

Psoriasis is a chronic, relapsing, immune-mediated dermatosis of accelerated keratinocyte turnover, classically presenting as sharply demarcated, silvery-scaled plaques on extensor surfaces, with guttate, inverse, pustular, and erythrodermic variants and an associated psoriatic arthritis. Mild-to-moderate disease is treated with emollients and topical corticosteroids with or without a vitamin-D analogue (calcipotriene 0.005% twice daily), while widespread (over 10% body surface area), recalcitrant, or severe disease escalates to phototherapy, methotrexate (weekly single dose 7.5 to 25 mg), or a biologic such as adalimumab, ustekinumab, or secukinumab, never a systemic glucocorticoid.

Sarcoidosis is a multisystem granulomatous disease of unknown cause defined by noncaseating granulomas, most commonly involving the lungs and hilar lymph nodes. Most patients are asymptomatic or have a self-limited course staged by chest radiograph; symptomatic organ-threatening disease is treated with systemic glucocorticoids, with methotrexate or another steroid-sparing agent added for glucocorticoid-refractory or glucocorticoid-intolerant disease.

Seborrheic dermatitis is a common chronic inflammatory reaction to Malassezia yeast that produces ill-defined erythema with dry or greasy scale in sebum-rich sites such as the scalp, nasolabial folds, brows, and ears. Diagnosis is clinical based on distribution; first-line treatment is topical ketoconazole cream or shampoo with a short course of low-potency hydrocortisone for inflamed flares, and disseminated or severe disease should prompt screening for HIV or a neurologic disorder.

Sjogren syndrome is a systemic autoimmune exocrinopathy in which lymphocytic infiltration of the lacrimal and salivary glands causes keratoconjunctivitis sicca and xerostomia, occurring alone (primary) or alongside another rheumatologic disease such as rheumatoid arthritis or lupus (secondary). Diagnosis combines the anti-Ro (SSA) and anti-La (SSB) antibody panel, objective dryness testing, and labial salivary gland biopsy under the 2016 ACR/EULAR classification criteria. Management centers on sicca-directed therapy, pilocarpine or cevimeline for xerostomia and topical cyclosporine for keratoconjunctivitis, with hydroxychloroquine or immunosuppression for extraglandular disease.

Lupus nephritis is immune complex glomerulonephritis arising from systemic lupus erythematosus, classified by kidney biopsy into ISN/RPS classes I through VI, with class III, IV, or V disease defined by proteinuria above 500 mg per 24 hours. Class-directed immunosuppressive induction pairs pulse glucocorticoids with mycophenolate mofetil or cyclophosphamide, followed by mycophenolate mofetil or azathioprine maintenance, on a background of hydroxychloroquine and renin-angiotensin-system blockade.