Systemic lupus erythematosus

Lupus erythematosus

Lupus erythematosus (LE) is a good example of such a spectrum, ranging from the purely cutaneous type (discoid LE), through patterns associated with some internal problems (disseminated discoid LE and sub-acute cutaneous LE), to a severe multisystem disease (systemic lupus erythematosus, SLE; Table 10.2).

Systemic lupus erythematosus

Cause

This is unknown, but hereditary factors, e.g. com-plement deficiency and certain HLA types, increase susceptibility. Particles looking like viruses have been seen in endothelial cells, and in other tissues, but their role is not clear. Patients with LE have autoantibodies to DNA, nuclear proteins and to other normal antigens, and this points to an autoimmune cause. Exposure to sunlight and artificial ultraviolet radiation (UVR), pregnancy and infection may precipitate the disease or lead to flare-ups. Some drugs, such as hydralazine and procainamide trigger SLE in a dose-dependent way, whereas others including oral contraceptives, anti-convulsants, minocycline and captopril, precipitate the disease just occasionally.

Presentation

Typically, but not always, the onset is acute. SLE is an uncommon disorder, affecting women more often than men (in a ratio of about 8 : 1). The classic rash of acute SLE is an erythema of the cheeks and nose in the rough shape of a butterfly (Figs 10.1 and 10.2), with facial swelling. Occasionally, a few blisters may be seen. Some patients develop widespread discoid papulosquamous plaques very like those of discoid LE; others, about 20% of patients, have no skin dis-ease at any stage.

Other dermatological features include peri-ungual telangiectasia (see Fig. 10.7), erythema over the digits, hair fall (especially at the frontal margin of the scalp), and photosensitivity. Ulcers may occur on the pal-ate, tongue or buccal mucosa.

Course

The skin changes may be transient, continuous or recurrent; they correlate well with the activity of the systemic disease. Acute SLE may be associated with fever, arthritis, nephritis, polyarteritis, pleurisy, pneu-monitis, pericarditis, myocarditis and involvement of the central nervous system. Internal involvement can be fatal, but the overall prognosis now is for about three-quarters of patients to survive for 15 years. Renal involvement suggests a poorer prognosis.

Complications

The skin disease may cause scarring or hyperpigmenta-tion, but the main dangers lie with damage to other organs and the side-effects of treatment, especially systemic steroids.

Differential diagnosis

SLE is a great imitator. Its malar rash can be confused with sunburn, polymorphic light eruption  and rosacea. The discoid lesions are distinct-ive, but are also seen in discoid LE and in subacute cutaneous LE. Occasionally, they look like psoriasis or lichen planus. The hair fall suggests telogen effluvium. Plaques on the scalp may cause a scarring alopecia. SLE should be suspected when a characteristic rash is combined with fever, malaise and internal disease (Table 10.3).

Investigations

Conduct a full physical examination, looking for internal disease. Biopsy of skin lesions is worthwhile because the pathology and immunopathology are dis-tinctive. There is usually some thinning of the epidermis, liquefaction degeneration of epidermal basal cells, and a mild perivascular mononuclear cell infiltrate. 

Direct immunofluorescence is helpful: IgG, IgM, IgA and C3 are found individually or together in a band-like pattern at the dermo-epidermal junction of involved skin and often uninvolved skin as well. Relevant laboratory tests are listed in Table 10.4.

Treatment

Systemic steroids are the mainstay of treatment, with bed rest needed during exacerbations. Large doses of prednisolone are often needed to achieve control, as assessed by symptoms, signs, erythrocyte sedimentation rate (ESR), total comple-ment level and tests of organ function. The dosage is then reduced to the smallest that suppresses the disease. Immunosuppressive agents, such as azathio-prine, cyclophosphamide and other drugs (e.g. antihypertensive therapy or anticon-vulsants) may also be needed. 

Antimalarial drugs may help some patients with marked photosensitivity, as may sunscreens. Intermittent intravenous infusions of gamma globulin show promise. Long-term and regular follow-up is necessary.

1   Do not wait for the laboratory to confirm that your patient has severe SLE: use systemic steroids quickly if indicated by clinical findings.

2 A person with aching joints and smallamounts of antinuclear antibodies probably does not have SLE.

3 Once committed to systemic steroids, adjusttheir dosage on clinical rather than laboratory grounds.