Categorising the various types of cutaneous manifestations of systemic disease is not easy. The following therefore is a random list of diseases most commonly encountered in practice which manifest themselves by changes in the skin:

Hyperlipidaemia¹

Skin manifestations of hyperlipidaemia include flat yellow deposits around the eye (xanthelasmata). Elsewhere on the body they present as yellowish papules or nodules called xanthomata. Sudden eruptions can appear in large numbers over the buttocks, trunk and limbs, or a few larger lesions can develop on the elbows, knees, hands and over the Achilles tendon.

Gastrointestinal disease

Inflammatory bowel disease

This can include pyoderma gangrenosum and erythema nodosum. Oral manifestations include aphthous stomatitis, mucosal nodularity (cobblestoning) and pyostomatitis vegetans (erythematous thickened mucosa). ²

Carcinoid syndrome

Cutaneous metastases can present as deep nodules, hyperkeratosis and pigmentation changes similar to those seen in pellagra.

Diabetes mellitus

Recurrent skin infections are common, either due to fungi (e.g. genital candidiasis) or bacteria (e.g. folliculitis). Blisters on the feet may be found as may granuloma annulare.³ Brown macules sometimes develop on the shin; when these blister the condition is called bullosis diabeticorum.⁴ Necrobiosis lipoidica diabeticorum can also occur on the shins. The lesions have the appearance of plaques with dark red or purple edges, atrophic centres and surface telangiectasia.

Liver disease

The cutaneous manifestations characteristically include:

• Jaundice
• Erythema of the palms
• Purpura
• Spider naevi
• Generalised itching

Lichen planus is known to be linked to hepatitis C infection.⁵

Human immunodeficiency virus/acquired immunodeficiency syndrome

A variety of skin conditions can occur in human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS):⁶

Dermatitis

The appearance can resemble psoriasis, Reiter's Disease or seborrheic dermatitis and has been termed 'psoriasiform dermatitis of AIDS'.⁶

Infections

Bacillary angiomatosis is a treatable infection caused by a rickettsia-like organism similar to Rochalimaea quintana, the agent of trench fever.⁷ Viral infections such as chronic herpes zoster can also occur.

Malignancy

Kaposi's sarcoma is an AIDS-defining illness characterised by initial bruise-like macules developing into brown-red or purple firm-to-hard nodules. In AIDS these are widespread, especially on the face and trunk.⁸

Sarcoidosis⁹

Sarcoidosis can present with erythema nodosum, or with plaques, papules or nodules. The latter are commonly seen as smooth, dark brown/violaceous lesions arranged in an annular pattern. Infiltration of an old scar is characteristic so that it becomes brightly purple coloured. Lupus pernio is a slowly developing form that spreads into large areas of plaque on the chin and nose.

Mastocytosis¹⁰

This is a condition in which there is proliferation of mast cells. In the skin it can cause single or multiple, dark red nodules or plaques that develop into a blister or wheal when rubbed. This is commonest in babies. It can also cause urticaria pigmentosa either as skin wheals in infancy often following a bath, or extensive areas of dark brown macules that swell and go red when stroked in adults.

Amyloidosis¹¹

Amyloidosis appears in middle age with bruising, petechiae and purpura related to deposition of amyloid in the dermal blood supply. This is most frequently seen in the anogenital, periorbital and peri-umbilical regions, at the side of the neck and in the axillae. Atrophic waxy lesions with areas of purpura inside them may sometimes be seen, the tips of the fingers may exhibit softening and loosening of the skin. A case of advanced primary amyloidosis presenting as a non-healing leg ulcer has also been reported.¹² Cutaneous amyloidosis is associated with various autoimmune/immune disorders and associations with sarcoidosis and IgA nephropathy have been reported.¹³

Acromegaly

Cutaneous changes in acromegaly can include skin puffiness, oily skin with large pores, hypertrichosis, pigmented skin tags, acanthosis nigricans and psoriasis.¹⁴ Skin creases in the head area are deeper than normal (cutis verticis gyrata or 'Klingon head').¹⁵

Hypopituitarism

The skin is dry, scaly and puffy and the nails become brittle. The hair is coarse and sparse, especially in the axillae. Fine wrinkles around the eyes and mouth are typical.¹⁶

Hypothyroidism

The skin in myxoedema is cool to the touch, doughy, dry and puffy and there may be hair loss. Peri-orbital oedema may be accompanied by a yellowish colour to the skin.

Hyperthyroidism

The skin in thyrotoxicosis is the obverse of that seen in myxoedema. It is warm and moist and flushing of the face and palms is sometimes seem. Pre-tibial myxoedema is characteristic.¹⁶

Cushing's syndrome

Abdominal striae may be a prominent feature, caused by skin atrophy. The skin may bruise easily and skin infections and acne may be frequent problems. Skin darkening may occur in the palmar creases, on areas subject to pressure and the axillae.^16,17

Porphyria

There are a number of different forms of porphyria, e.g. porphyria cutanea tarda, erythropoietic porphyria. All are characterised by photosensitivity, with fragility and blistering of the skin when exposed to sunlight or ultraviolet rays.^18,19

Rheumatoid arthritis²⁰

Rheumatoid nodules - subcutaneous lumps seen near an affected joint - occur in about 25% of patients. Other phenomena include thinning of the skin, translucency of the skin on the back of the hands, brittle nails which split lengthwise and reddened palms (palma erythema). Dermatitis in which neutrophils are prominent on biopsy (neutrophilic dermatosis) may present as erythematous areas, and interstitial granulomatous dermatitis is a rare condition in which rheumatoid papules may appear on the trunk. Cutaneous vasculitis may present as purpuric areas on the skin.

Reiter's disease

Keratoderma blennorrhagicum is sometimes seen in this condition. It is characterised by hyperkeratotic lesions on the palms of the hands or the soles of the feet. Clear vesicles on an erythematous base develop which then progress to macules, papules and nodules. The lesions may be impossible to distinguish from pustular psoriasis.²¹

Myelodysplastic syndrome

Various cutaneous manifestations can occur including leukaemia cutis, photosensitivity, prurigo nodularis and purpura. Cutaneous conditions are thought to indicate that the patient belongs to a high-risk group, associated with bone marrow transformation and hypergammaglobulinaemia.²²