Herpes simplex

Caused by a neurodermotropic virus, herpes simplex is an infectious dermatitis with vesicles and an acute course.

Usually the first contact with the virus occurs in the first years of life and may be asymptomatic or be manifested with stomatitis, herpetic vulvitis or more rarely skin herpes.

Signs and symptoms

It is manifested with a red patch, oedematous to a larger or lesser extent, on which the typical herpetic vesicles appear in clusters. The vesicles, varying in size from 1 to 3 mm, contain serum which can subsequently become purulent. In a few days, usually 3 or 4, the vesicles dry or break giving rise to polycyclic erosions which are covered with yellowish-brown adherent crusts. Healing takes place with complete return to the original condition. The sequelae may be a short-lasting erythematous patch. There may also be inflammatory lymphadenopathy of the regional lymph nodes. Sometimes the symptoms are preceded by a feeling of tension or burning.

Herpes simplex tends to recur at variable intervals and always in the same location. Depending on the location, labial herpes, cutaneous herpes and genital herpes may be distinguished. Sometimes the conjunctiva and cornea may also be involved, where severe corneal ulcers and leucomas may arise (Fig. 1-7).

Diagnosis

Diagnosis is based on the direct cell diagnosis test, which shows cells undergoing ballooning degeneration, and the HSV PCR molecular test which detects DNA on a skin swab.

Particular forms

Eczema erpeticum or Kaposi varicelliform eruption

This usually presents in the first year of life in subjects with atopic dermatitis. It arises following contact with a subject with herpes simplex and it usually initially affects the eczema patches of the face and tends to disseminate vesicles which evolve with successive outbreaks. The lesions may develop a haemorrhagic appearance. There is fever and signs of general malaise. Possible complications are herpetic keratitis, bronchopneumonia and meningoencephalitis. Risk factors are the severe forms of atopic dermatitis and high IgE values (Fig. 8).

Differential diagnosis is with eczema coxsackium

The virus in question is Coxsackievirus A6 or A10 responsible for the atypical forms of hand-foot-mouth disease. This virus favours injured skin areas and affects the perioral and perianal regions, which are usually spared in the classic form. In the atopic subject, the vesicular lesions develop on the eczema patches (Fig. 9-12).

Post-herpetic exudative erythema multiform

If secondary to the herpes simplex virus infection, exudative erythema multiform is characterised by erythematous-papular or vesicular-bullous symptoms that affect symmetrically the extremities, extensor regions of the limbs, head and ears. Subjective symptoms are a feeling of burning and pain. In some cases there may also be generalised symptoms with fever and arthromyalgia. The dermatosis progresses spontaneously, sometimes with successive outbreaks, until it resolves spontaneously; recurrent forms are reported which follow the course of the triggering herpetic infection (Fig. 13-15).

A differential diagnosis of cutaneous herpes simplex is mainly with impetigo (Fig. 16) and acute eczema (Fig. 17).

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