Skin changes in internal conditions

Skin signs are seen with many internal disorders and are not uncommonly their presenting feature. The astute dermatologist can recognize undiagnosed systemic disease. Skin changes are common in pregnancy ( Chapter 69 ). Sometimes itch alone is the primary symptom.

Skin signs of endocrine and metabolic disease

Almost all endocrine diseases (and several metabolic defects) have cutaneous signs that depend on the over- or underproduction of a hormone or metabolite ( Table 47.1 ).

Table 47.1

Skin signs of endocrine and metabolic disorders

Disorders	Skin signs
Diabetes mellitus	Necrobiosis lipoidica, granuloma annulare, xanthomas, Candida albicans infection, ‘dermopathy’, neuropathic ulcers
Thyrotoxicosis	Pink soft skin, hyperhidrosis, alopecia, pigmentation, vitiligo, onycholysis, clubbing, pretibial myxoedema, palmar erythema
Myxoedema	Alopecia (including eyebrows), coarse hair, dry puffy yellowish skin (e.g. hands, face), asteatotic eczema, xanthomas
Addison’s disease	Pigmentation (p. 75), vitiligo, loss of axillary and pubic hair
Cushing’s disease	Pigmentation, hirsutism, striae, acne, obesity, buffalo ‘hump’
Acromegaly	Thickened moist greasy skin, pigmentation, skin tags
Phenylketonuria	Fair hair and skin, atopic eczema (p. 36), photosensitivity
Hyperlipidaemia	Xanthomas (tuberous, tendinous, eruptive, plane), xanthelasma
Cutaneous porphyrias	Photosensitivity, blistering, skin fragility, atrophic scarring, thickening of skin, hypertrichosis, pigmentation (p. 46)

Diabetes mellitus

Candida albicans or bacterial infection is more common with untreated or poorly controlled diabetes. The neuropathy or arteriopathy of diabetes may result in ulcers on the feet (p. 90), and an associated secondary hyperlipidaemia can produce eruptive xanthomas (see Fig. 47.1 ). Diabetic dermopathy describes depressed pigmented scars on the shins, associated with diabetic microangiopathy. Necrobiosis lipoidica ( Fig. 47.2 ), characterized by shiny atrophic yellowish–red plaques on the shins, was associated with diabetes in 65% of cases in one series, although others find a much lower figure. It affects less than 1% of all diabetics. Histologically, degenerate dermal collagen is seen with epithelioid cells and giant cells. The condition is chronic and may ulcerate. It is unresponsive to treatment. In contrast, granuloma annulare —recognized as palpable annular lesions on the hands, feet or face ( Fig. 47.3 )—is only rarely associated with diabetes and usually fades in 2 years. It must be differentiated from tinea corporis.