Only the changes seen in porphyria cutanea tarda are considered here. Similar changes in the skin may be seen with variegate porphyria and hereditary coproporphyria. Cutaneous lesions occur on exposure to sunlight. These consist of increased fragility of the skin over the dorsum of the hands, fingers and face and are associated with erythema, blistering and scarring. Hypertrichosis on the sides of the face and between the eyebrows and hair margin is common and may be associated with facial skin thickening and loss of hair (pseudoscleroderma). Hyperpigmentation or loss of pigment may also be seen on the facial skin. Itching may be troublesome.
Cutaneous forms of the disease may be widespread on the skin and mucosal surfaces or localized to particular areas. The skin is involved in about 40% of patients who have systemic amyloidosis in association with diseases such as myelomatosis.
The gums may appear nodular and waxy and bleed easily on trauma. Pale yellow-brown papules may appear over the basal conjunctivae and at other mucosal sites and purpura is seen following mild trauma. Sites of predilection elsewhere on the skin include the eyelids, the nasolabial folds, the sides of the neck, and the flexural surfaces. Thickened indurated plaques may rarely affect the chest, abdomen or hands. Cutaneous changes are rare in the hereditofamilial patterns of disease.
Cutaneous disease where there is no evidence of systemic spread is seen in two forms: macular and lichen amyloidosis.
Macular amyloidosis is quite commonly seen on the shoulders, neck or upper back of patients of Asian origin. The hyperpigmented macular changes have a rippled appearance likened to the changes seen on a sandy beach at low tide. Patients are only concerned about the appearance of the lesions, which are dark grey/black in colour.
The amyloid material is difficult to demonstrate on histology using routine methods.
Lichen amyloidosis is an uncommon papular eruption that is often pruritic and occurs on the lower limbs. There is no explanation for the appearance of the amyloid material at this site. Other pruritic diseases on the lower legs are often hypertrophic, especially in patients of African or Asian origin. Diseases such as hypertrophic lichen planus and lichen simplex may resemble the disease on superficial inspection. Close examination should, however, distinguish these diseases. The shiny, warty, close-set papules of lichen amyloidosis are characteristic of the disease.
C N S-RELATED DISEASES
The number of dermatoses that have been associated with diseases of the nervous system is large but most are extremely rare.
The characteristic cutaneous features are hyperpigmentation (cafe-au-lait spots) and flesh-coloured smooth polypoid swellings, i.e. neurofibromas. Molluscum fibrosum (skin tags) are sessile pink-coloured tumours that are often numerous over the trunk. Plexiform neuromas are uncommon and tend to follow the course of a nerve, usually on the face or neck. In some areas there is overgrowth of skin and subcutaneous tissue in addition and this may give rise to gross disfigurement (elephantiasis
neuromatosa). Oral lesions occur in up to 10% of patients.
Cafe-au-lait spots may suggest the diagnosis in children but there should be more than five in number to support it. The pigmentary changes must be differentiated from those seen in Albright’s syndrome (see p. 782). In neurofibromatosis the cafe-au-lait spots show histologically the presence of giant melanosomes; these are rare in Albright’s disease.
SEGMENTAL DISEASE. Cafe-au-lait patches and neurofibromata may be confined to a body segment.
Tuberous sclerosis (epiloia)
The cutaneous lesions in tuberous sclerosis are derived from connective tissue and are of several different types.
Adenoma sebaceum are erythematous papules or nodules on the cheeks or within the folds at the sides of the mouth or nose. The turn ours are vascular and fibrous in origin. Periungual fibromas occur as pink, firm, claw-like tumours arising from and around the nail folds. Shagreen patches are flesh-coloured tumours that are firm and plaque-like. They often have a wrinkled surface and are most frequently seen over the lumbosacral region. Areas of macular hypopigmentation occur in ovoid or leaf-like shapes. They may be seen over the trunk or back and are most easily detected by examination with Wood’s light. They appear early in childhood, associated in many cases with mental retardation.
Small erythematous papules on the face and cheeks may be treated with an electrical Hyfrecator or cautery.
Other CNS-related diseases
Naevoid lesions may be seen in conjunction with neurological disease; for example, in the epidermal naevus syndrome, pigmented naevi occur in a linear fashion on the limb or trunk and may be associated with epilepsy or mental retardation.
Gross ichthyotic changes may occur on the skin of patients with spastic diplegia and mental retardation in the Sjogren-Larsson syndrome.
The skin can be involved by both primary and secondary tumours. Table 20.4 shows some cutaneous markers of malignant disease which may be associated with genodermatoses, paraneoplastic dermatoses or environmental carcinogens, e.g. arsenic, vinyl chloride, ionizing radiation.