OVERVIEW

HIV infection leads to a progressive fall in the CD4 count with resultant immunosuppression and, if untreated, eventually AIDS.
A widespread maculopapular rash occurs in 50% of patients during primary HIV infection.
Cutaneous eruptions in the context of HIV are common, atypical and frequently severe.
Common skin complaints associated with HIV include nodular prurigo, seborrhoeic dermatitis and pruritic papular eruption.
Adverse drug eruptions are common in HIV patients, from mild toxic erythema to severe life-threatening toxic epidermal necrolysis.
Skin conditions often improve as the immune system is restored with antiretroviral therapy.
As the immune system reconstitutes there may be a brisk inflammatory response to high levels of antigen building up in chronic infections.

Introduction

The human immunodeficiency virus (HIV) is the cause of the acquired immune deficiency syndrome (AIDS). Worldwide, 34 million children and adults are currently living with HIV according to current WHO (World Health Organization) statistics (2013). 54% of those with HIV eligible for antiretroviral therapy have access to it. As yet there is no effective vaccine against HIV. Methods for reduced transmission of HIV include condoms, voluntary male circumcision, prevention of mother-to-child transmission, sterile injection equipment, screening blood products and pre-exposure prophylaxis for serodiscordant couples. Trials of pre-exposure prophylaxis with tenofovir disoproxil fumarate (TDF) 300 mg alone or with emtricitabine 200 mg have shown to reduce the risk of acquiring HIV by 60–90% depending on adherence.

HIV is an RNA retrovirus that replicates itself by reverse transcriptase to produce a DNA copy; this then becomes incorporated into the host DNA where further replication occurs. HIV persists in the body within the host’s immune cells—the CD4 lymphocytes and monocytes—thereby directly weakening the host’s immune system. Initially, the virus remains latent for an average of 10 years before causing profound immunosuppression. The extent to which an individual’s immune system is affected by HIV is measured through the CD4 cell count and the HIV viral load. AIDS is defined as a CD4 count of less than 200 cells/µl, or HIV associated with any one of 26 (mainly opportunistic infections) conditions.

Patients with low CD4 counts who are profoundly immunosuppressed tend to have more frequent and more severe skin disorders. Common cutaneous diseases such as psoriasis, eczema, seborrhoeic dermatitis (SD) and acne tend to be more severe, have atypical features and are often resistant to conventional treatments. The spectrum of cutaneous manifestations in HIV has changed over the past decade because of the use of highly active anti-retroviral therapy (HAART). This treatment, however, is only available to 54% of individuals who need it and despite treatment 70% of patients still suffer from HIV-related skin problems with a high incidence of adverse drug rashes. In addition, patients taking HAART can develop problems when their immune system is reconstituted—the so-called immune reconstitution inflammatory syndrome (IRIS). In IRIS, the brisk inflammatory response relates to the immune system ‘waking-up’ to the presence of antigen previously unrecognised such as genital herpes simplex virus (HSV).

In general, HIV/AIDS should be considered in any patient with a florid or atypical inflammatory skin disease that is resistant to treatment or who has severe and extensive infection of the skin. Because of the atypical nature of cutaneous manifestations in HIV medical practitioners should have a low threshold for performing a skin biopsy for histology and culture (Box 15.1). Many modern heath care systems are introducing HIV screening for all patients newly registering at primary care facilities in the community or any patient who attends their local hospital. Diagnosing and treating those with HIV early on in the disease will result in less morbidity, less premature mortality and reduced onwards transmission and ultimately be cost-effective.

Box 15.1 HIV and the skin

Skin disorders affect 80% of HIV patients.
Fifty percent develop a rash during the primary HIV infection so-called ‘seroconversion’.
Severity of skin disorders usually increases with decreasing CD4 counts.
Cutaneous presentations are frequently atypical.
Consider taking a skin biopsy for histology and culture in any HIV patient with a rash.
Management of skin diseases can be difficult; HAART is usually beneficial.
Patients have a high risk of developing adverse drug reactions.

Stages of HIV

Primary HIV infection

Eighty percent of individuals have acute signs and symptoms associated with their primary HIV infection—the so-called ‘seroconversion illness’. The incubation period is 2–6 weeks. Symptoms include fever, malaise, headache, nausea, vomiting and diarrhoea. Clinical signs include cervical lymphadenopathy, pharyngitis, weight loss and rash. The skin eruption associated with primary HIV infection is present in 50% of patients and consists of a maculopapular rash mainly on the face, neck and trunk lasting 2–3 weeks (Figure 15.1). Some patients develop a papulovesicular eruption or erosions in the mouth rather than a classic viral exanthem. During seroconversion abnormalities in the full blood count (FBC) may be seen (leukopenia, lymphopenia, thrombocytopenia, low haemoglobin) and diagnostically HIV RNA may be detected in the plasma.

c15f001 — **Figure 15.1** Primary HIV infection: seroconversion rash.

Early stages

Within 1–2 months of the primary infection, 50% of patients will have detectable antibodies to HIV. The proportion of CD4 lymphocytes variably decreases and this is associated with an increased frequency and severity of skin disorders. Patients may experience worsening of premorbid skin complaints such as psoriasis or present de novo with sudden florid skin disease such as SD. Adverse drug reactions are more frequent and often severe.

Late-stage HIV infection

As the patient’s immune system becomes increasingly suppressed and the CD4 count falls below 200 cells/µl he or she is classified as having AIDS. Patients with AIDS may present with severe widespread dermatoses including SD, crusted scabies, multidermatomal varicella zoster virus, Kaposi’s sarcoma, widespread fungal/yeast infections, bacillary angiomatosis (BA) and eosinophilic folliculitis (EF). These conditions are described in more detail below.