About one-quarter of patients with systemic sarcoidosis have skin lesions. There are many variants:
ERYTHEMA NODOSUM (see p. 1005), a non-specific reaction.
NODULES, PAPULES AND PLAQUES, red/blue or brown are seen particularly on the face, nose, ears and neck in chronic sarcoid. This is the most common specific form seen in Caucasians.
ANNULAR, MACULAR LESIONS with central depigmentation are less common.
MICROPAPULAR LESIONS are common in Afro- Caribbeans and are usually the same colour as the skin.
They occur around the nasal alae within the vestibules, on the lips or cheeks or over the periorbital .
Lupus PERNIO, an uncommon variant, affects the nose with a diffuse bluish plaque with small papules within the swelling.
WIDESPREAD CUTANEOUS SARCOIDOSIS is often papular or nodular. Occasionally, subcutaneous nodules are found. Sarcoidosis may appear in old scars.
Differential diagnosis of facial lesions includes leprosy and tuberculosis. Blue nodular lesions should be differentiated from lymphomas.
Most cutaneous forms of sarcoidosis will improve with increasing doses of systemic steroids. Drugs such as methotrexate, mepacrine or chloroquine may help in reducing the dose of steroid required. Intralesional steroids can aid resolution on occasions. Lesions may often recur on withdrawal of drugs.
Cutaneous abnormalities occur in more than 25% of patients with diabetes mellitus. They may be non-specific, such as infection with candidiasis, or so distinctive that the dermatologist may be able to predict the diagnosis of diabetes mellitus.
Secondary causes of diabetes (see p. 830), e.g. haernochromatosis and liver disease, may in themselves have cutaneous manifestations and these features are described under the appropriate disease heading.
Necrobiosis lipoidica (diabetic forum) The association of this condition with diabetes is unpredictable; 50% of such cutaneous changes occur in nondiabetic patients. Necrobiosis lipoidica is an unusual complication of diabetes and is not necessarily related to other vascular complications. Nevertheless, small-vessel damage is thought to be a central feature of the pathogenesis. There is partial necrosis of dermal collagen and connective tissue and a histiocytic cellular response. It is more common in females, and presents in young adults or early middle life.
The skin over the shins is the site principally involved and pigmentary changes may cause the casual observer to associate the eruption with venous incompetence. On close examination the features are characteristic: erythematous plaques are seen that gradually develop a brown waxy discoloration that is more evident when stretching the skin. The skin’s blood vessels are prominent because of the associated atrophic changes in the dermis. Fibrosis and scarring from previous ulceration may also be seen . Treatment is with support bandaging. The use of an antiseptic powder or spray such as povidone-iodine is useful when the skin is broken. Non-adhesive dressings should be used. Low-dose aspirin may help to improve the healing of such lesions.
This is a common finding on the shins of diabetics. Initially the lesions are erythematous and papular but tend with time to become flat, hyperpigmented and atrophic. The changes are often seen in association with microangiopathy elsewhere. The pathogenesis of these lesions, which are not specific to diabetes mellitus, is unclear, although intimal thickening of small blood vessels has been demonstrated.
Diabetic stiff hands
This condition was first described in patients with juvenile- onset diabetes, but similar changes have been seen in middle-aged diabetics.
Tight, waxy skin principally affects the dorsum of the fingers and is associated with joint stiffness that can limit extensor movements of the small joints (cheiroarthropathy). Histological sections demonstrate thickening of dermal collagen.
This condition is seen as a spreading erythema and induration of the skin that starts on the neck and the upper trunk of middle-aged diabetics. These changes are often heralded by a respiratory illness or by streptococcal infection. The lesion may become generalized over the trunk, limbs, hands and feet, although the genitalia tend to be spared. There is a spontaneous resolution with time.
This is an unusual complication in which blisters develop on the feet and occasionally the hands. They are of an acute onset and occur without any obvious preceding trauma. The disease is sometimes associated with an extensive polyneuropathy. Histological section shows a cleft in the region of the lamina lucida but the cause is not known. Blisters clear in 2-5 weeks.
This presents as flesh-co loured papules in annular or crescentic configurations, principally over the extensor surface of the joints of the fingers (Fig. 20.17). The feet, ankles, hands and wrists may be similarly affected. A disseminated pattern is probably triggered by sunlight but often involves covered areas of skin.
The association of such lesions with diabetes mellitus remains controversial; a few cases do not have overt diabetes but only impaired glucose tolerance. The pathology is similar to necrobiosis lipoidica and the two conditions may occur together.
These may appear suddenly as crops of yellow papules on the knees, elbows, back and the buttocks. They are associated with hyperlipidaemia and are seen most commonly in diabetics. They resolve with the control of the diabetes and hyperlipidaemia.
Other skin disorders
Infections and lipodystrophies are often seen in diabetes mellitus; they are discussed in Chapter 17. Skin breakdown may occur especially in association with peripheral vascular disease and give rise to gangrene, synergistic (aerobes and anaerobes) necrotizing cellulitis, progressive bacterial synergistic (microaerophilic, streptococci, Staph. aureus or enteric Gram-negative bacilli) gangrene.