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398 Chapter 9: Dermatology and soft tissues

Table 9.7 Causes of hypertrichosis Aetiology/pathophysiology
ThecommonestcauseofimpetigoisStaph.aureus;group
Drugs Phenytoin, penicillamine, minoxidil,
ciclosporin A Streptococci also cause impetigo. Increased incidence
Systemic illness Hypothyroidism, anorexia nervosa, of impetigo is seen in conditions damaging the integrity
malnutrition, porphyria cutanea of skin such as eczema, and its spread is facilitated by
tarda overcrowding and poor hygiene.
Paraneoplastic
syndrome
Clinical features
Impetigo appears as erythematous erosions with a char-
Investigations acteristic golden brown crusting. There may be associ-
Dependent on the level of virilisation and menstrual ated localised lymphadenopathy. Bullous impetigo de-
anomaliesfound;hormoneprofileandabdominalimag- scribes punched-out blistering lesions with crusting due
ing may be required. to Staphylococcal toxin production.

Management Management
Any underlying cause for excess androgen production
Swabs should be taken. Localised disease may be
should be identified and treated. treated with topical agents such as fucidin cream. Of-
Physical methods of hair removal include shaving,
ten the condition requires treatment with oral penicillin
chemical depilatories, bleaching, electrolysis and laser (Streptococcus) and flucloxacillin (Staphylococcus). Ery-
treatments. thromycin is an alternative for penicillin-sensitive indi-
Combined oral contraceptives may slow hair growth; viduals.

antiandrogens may also be effective.
Cellulitis
Hypertrichosis
Definition
Definition Cellulitis is an acute diffuse spreading infection of the
Hypertrichosis is excessive hair in a non-androgenic dis- skin extending into the soft tissues. Erysipelas is an acute
tribution. Causes of hypertrichosis are given in Table 9.7. infection of the skin not extending into the soft tissues.

Clinical features Aetiology/pathophysiology
Patients present with fine terminal hair diffusely on the The main causative organisms are β-haemolytic Strep-
face, limbs and trunk. As there is often an underlying tococci and Staph. aureus.Risk factors for development
cause, thorough investigation is indicated. of cellulitis include damage to skin integrity (leg ulcer,
traumatic wounds), venous insufficiency, leg oedema,
diabetes and obesity. The mechanisms of infection are
Infections of the skin and not clearly understood but may involve bacterial exotox-
soft tissue ins and cytokine release.

Clinical features
Bacterial infections
Patients have a well-demarcated patch of erythema with
swelling of the underlying soft tissues. There is warmth
Impetigo
andtendernesstotouch,oftenwithlocallymphadenopa-
Definition thy. If untreated, there is spreading of the erythema,
Impetigo is a contagious superficial skin infection oc- abscess formation and secondary septicaemia. Systemic
curring on exposed skin predominantly in children. symptoms may include fever, fatigue and myalgia.