Common Skin Infections

Hidradenitis suppurativa

I have included this condition under BOILS, although it is not a true staphylococcal/streptococcal infectious boil as such, but rather an inflammatory one which may be part of the so-called Follicular Occlusion Tetrad of conditions- Hidradenitis, Dissecting Cellulitis, Acne Conglobata and Pilonidal sinus. I have put it here though as patients usually present with what they describe as 'recurrent boils', and it is an important condition to be aware of. Fortunately it is a relatively rare condition but one which causes a vast amount of suffering to the patient.

It is characterised by a painful, discharging, chronic inflammation of the skin at sites rich in apocrine glands (axillae, groins, natal cleft). Patients tend to be females usually, but not always, with a high BMI and within some families it appears to be inherited in an autosomal dominant fashion. It presents after puberty with paired comedones, papules, nodules and abscesses which often progress to cysts and sinus formation. Lesions are in the axillae, groin, natal cleft and buttocks. Complications include fistulae, keloid scars, lymphoedema and contractures. The condition follows a chronic relapsing remitting course and aggravated by obesity, smoking and certain drugs e.g. Lithium. It is thought to be multifactorial - hormones, infection, apocrine gland structure and genetic predisposition (PSENEN & NCSTN genes).

Treatment is very difficult, particularly in moderate and severe disease and involves lifestyle measures such as stop smoking, lose weight, topical antispetics e.g. Chlorhexidine as soap. Mild disease can be managed with topical antibiotics such as Erythromycin and Clindamycin, along with staph elimination and bleach baths.

There are a number of therapeutic options for more severe disease which can often be very difficult to control, and include oral antibiotics: Tetracyclines, Clindamycin +/- Rifampicin, oral antiandrogens, isotretinoin/acitretin and in very severe cases biologic therapy with Infliximab. Surgery may be indicated. There is some suggestion that oral zinc sulphate 10mg/kg max 400-600 mg daily may be helpful in Hidradenitis, and a number of case reports using axillary Botox have suggested that this may be of benefit also.

Hidradenitis- typical locations and note typical bridging scarring in axilla.

Echthyma

This is an infection due to streptococcus or staphylococcus aureus or occasionally both which is rare in the UK but seen more commonly in debilitated, intravenous drug abusers immunosuppressed people (e.g. HIV), diabetics, the homeless alcoholics etc. It is more common in developing countries, being associated with poor nutrition and hygiene. Typically, chronic well demarcated, round, ulcerative lesions sometimes with an exudative crust are seen usually on the lower legs. Eschar like appearances can be noted and associated ulceration can be deep. It can usually be treated with oral antibiotics but remember if you do encounter a case to look for an underlying cause.

Echthyma – note the deep, black, crusted ulcers