Introduction
This topic covers the purulent infections of the skin and its appendages: folliculitis, furuncle (boil), carbuncle and hidradenitis suppurativa. The first three are acute bacterial infections centred on the hair follicle and the dermis or subcutis, usually caused by Staphylococcus aureus. Hidradenitis suppurativa is a chronic, recurrent inflammatory disease of apocrine-gland-bearing skin that is often complicated by abscesses and sinus tracts. In the exam, the key is to distinguish depth, extent, systemic involvement and the correct local and general treatment.
Folliculitis
Folliculitis is inflammation of the hair follicle. It is superficial when confined to the upper part of the follicle, and deep when the process extends into the follicle wall and surrounding dermis, where it becomes a furuncle.
- Causes: most often Staphylococcus aureus; shaving, friction, occlusion, sweating, obesity, diabetes and prolonged antibiotic use (which may select gram-negative organisms such as Pseudomonas aeruginosa, for example in hot-tub folliculitis).
- Clinical picture: small pustules centred on hair follicles, mild itching or tenderness, with no systemic signs in localised cases.
- Treatment: hygiene, stopping shaving or occlusion, and topical antiseptic or topical antibiotic such as mupirocin for localised disease; systemic antibiotics for extensive or recurrent cases, guided by local resistance patterns; correction of diabetes where present.