The skin is frequently involved in systemic diseases. In this section, only conditions with major cutaneous manifestations that are not dealt with elsewhere are considered.
These systemic diseases often have cutaneous manifestations, which are described here.
Systemic lupus erythematosus
Photosensitivity is a presenting feature in about one-fifth of patients and may occur with a greater frequency as the disease progresses.
The nose, cheeks (butterfly distribution), forehead, ears and the backs of the hands are affected by the nonspecific changes of diffuse erythema or maculopapular lesions; blistering may accompany more acute disease. More chronic changes on the backs of the hands or fingers include blue/red discoloration of the skin, reticulate patterning or poikiloderma (i.e. scarring, atrophic changes and vessel prominence combined with erythema). Nail-fold capillary dilatation and ragged cuticles with haemorrhages are seen in this disease, as well as in dermatomyositis and systemic sclerosis. Loss of tissue over finger pads associated with Raynaud’s phenomenon (see p. 628) is seen, although this is a more prominent feature in systemic sclerosis or mixed connectivetissue disease. Purpura and urticaria may be presenting features of SLE or they may accompany a more widespread vasculitis.
Alopecia occurs with either broken hairs, most noticeable over the frontal region, or diffuse hair loss associated with more severe generalized disease.
Protection against the sun is important.
Cutaneous (discoid) lupus erythematosus
This condition represents disease that is almost totally confined to the skin. There are two different patterns: 1 Discoid lesions involving principally facial skin 2 Widespread cutaneous disease, when the hands, feet, limbs and trunk may also be affected Patients with widespread cutaneous disease may develop SLE, whilst patients with SLE may develop chronic discoid lesions.
Arthropathy, Raynaud’s phenomenon, haematological abnormalities, a raised ESR and abnormal serological findings are sometimes seen with disease, which is seemingly limited to the skin. It may be difficult, therefore, to decide whether a patient has just cutaneous disease or a systemic illness. Obvious ill-health, high levels of DNA binding and hypocomplementaemia, a positive lupus band test (typical immunofluorescent changes seen on a biopsy, suitably stained and taken from normal uninvolved skin) are important findings in SLE and these may help to differentiate the two conditions.
Women are twice as frequently affected as men, in contrast to SLE where the female-to-male ratio is 9 : 1. The peak incidence is later than SLE-between 40 and 50 years. In discoid lupus erythematosus the face, neck and, less commonly, the scalp are the principal sites of involvement. Erythematous scaled plaques, oval or round or contoured in outline may be seen (Fig. 20.13). Follicular plugging is characteristically seen; this may be demonstrated as spikes of keratin seen on the under-surface of a removed scale. Atrophy and scarring are common features and when these occur on the scalp permanent hair loss follows. Although sunlight is an exacerbating factor in most patients, other forms of trauma to the skin, such as cold injury, may trigger the onset of new lesions or reactivate areas of previously involved skin.
Widespread, cutaneous disease may demonstrate similar morphological features, although scaling is not so pronounced. Reticulate patterning or smooth, shiny, red/blue, atrophic skin is seen, especially on the fingers or plantar aspect of the toes. Chilblain-like lesions may be seen at the same sites and on the heels or earlobes
Suitable protection from strong sun or cold should be worn. High-protection-factor sunscreens need to be applied regularly. Hydroxychloroquine in doses of 200- 400 mg daily during spring and summer gives extra protection from sunlight and settles inflammatory changes.
Prolonged treatment at high dosage can produce permanent retinal damage so that an ophthalmic opinion should be sought prior to starting treatment and at regular intervals thereafter. Oral prednisolone is given for more florid cutaneous disease.
Potent topical corticosteroids may improve cutaneous lupus erythematosus; this disease is one indication for their application to facial skin. Treatment may need to be intensified when acute inflammatory changes affect the scalp so that scarring and permanent hair loss are prevented.
Other agents that have been used for recalcitrant patterns of disease include thalidomide, mepacrine, vitamin E and retinoids.