HIV infection commonly causes significant dermatological problems. A rash may even be the presenting feature of underlying HIV infection. It is estimated that 90% of HIV-positive patients will suffer with a mucocutaneous disorder during the illness. It is also estimated that up to 30% of people with AIDS will suffer from three different dermatoses. These rashes can often be clinically atypical and difficult to diagnose. One must have a low threshold for skin biopsy and skin culture. On top of this many of the skin problems are resistant to standard treatments. Most of these dermatoses have become less prevalent since the advent of HAART.

Cutaneous infection and opportunistic infection

Not surprisingly, infections are increased because of the HIV-induced immune deficiency. Molluscum contagiosum are particularly common especially on the face. They are often multiple and of a 'giant' size measuring over 1 cm across. Molluscum are rarely seen in adults and they can be the presenting feature of HIV. Other viral infections such as extensive ulcerative herpes or widespread viral warts may be seen. Bacterial infections (e.g. staphylococcal boils) and fungal infections (e.g. ringworm and Candida) are also common. Recalcitrant and recurrent oropharyngeal candidiasis is a particular problem.

Opportunistic infections such as cutaneous cytomegalovirus (pustules or necrotic ulcers), sporotrichosis (linear nodules) or cryptococcus (red papules, psoriasiform or molluscum-like lesions) can pose diagnostic difficulties, stressing the need for skin biopsy and culture.

Inflammatory dermatoses

Inflammatory dermatoses show an increased incidence with HIV infection, probably due to an immune dysfunction or imbalance rather than as a consequence of immune suppression. Severe, extensive seborrhoeic eczema is very common and may be a presenting sign of HIV. Other types of eczema, psoriasis, ichthyosis (dry scaly skin), nodular prurigo and pruritus are all common in HIV infection and can be very severe. Granuloma annulare and lichen planus are probably increased in incidence. The treatment of these conditions is difficult as oral immunosuppressive therapies (e.g. prednisolone, ciclosporin) are best avoided in patients with low CD4 counts. Topical therapies and phototherapy seem relatively safe. Oral retinoids are useful in the management of psoriasis.

'Autoimmune dermatoses'

Bullous pemphigoid, thrombocytopenic purpura, and vitiligo seem to be increased in incidence. The polyclonal stimulation of B lymphocytes by HIV and the resulting abnormal antibody production may be involved in their aetiology. Erythroderma is sometimes seen in HIV disease where skin biopsy suggests a 'graft-versus-host disease' mechanism. This presumably reflects a severe underlying immune dysfunction of T lymphocyte control.

Drug rashes

Adverse drug rashes are much commoner in HIV patients. Reactions to co-trimoxazole, dapsone and antiretroviral drugs appear particularly common. Drug rashes may be severe (especially with nevirapine) resulting in erythroderma or toxic epidermal necrolysis. Other unusual rashes include a striking nail/mucosal pigmentation from zidovudine, paronychia from indinavir and facial lipodystrophy mostly from protease inhibitors.

Cutaneous tumours

Kaposi's sarcoma is much commoner in homosexuals with HIV than in other groups. Basal and squamous cell carcinomas and benign melanocytic naevi are also a little increased in incidence, presumably reflecting a loss of immune surveillance.

'Specific' HIV dermatoses

'Itchy folliculitis' of HIV (also called papular pruritic eruption)

Itchy follicular eruptions are common in HIV as CD4 counts decline. The previously described staphylococcal folliculitis, eosinophilic folliculitis, pityrosporum folliculitis, and demodex mite folliculitis are probably all part of a spectrum and the term itchy folliculitis is useful to encompass these. It presents with intensely itchy papules centred on hair follicles and occurring most commonly over the upper trunk and upper arms. The face is more commonly involved in black patients. Individual lesions frequently have the top scratched off, leaving a crateriform appearance. The aetiology is unknown but may reflect a hypersensitivity reaction as high IgE and eosinophil counts may be present.

Treatment with oral minocycline, potent topical steroids and emollients may help. Phototherapy or oral isotretinoin is useful in resistant cases.

Oral hairy leucoplakia

This is characterized by white plaques with vertical ridging on the sides of the tongue. Unlike with oral Candida, the lesions cannot be peeled off to leave raw areas underneath. It was first recognized in HIV disease but can rarely occur in other forms of immunosuppression. It is thought to be due to co-infection with Epstein-Barr virus.

Treatment with aciclovir, ganciclovir or foscarnet may help.