subject: Follicular infections and differential diagnosis [print this page] Follicular infections and differential diagnosis
A furuncle (boil) is an acute necrotizing infection of a follicle.A carbuncle is more extensive, involving contiguousfollicles and the tissues around them. Infection of the hairfollicle opening is termed superficial folliculitis.The usual infecting organism is Staph. aureus, and thereis often nasal, axillary or perineal carriage of the organism.Friction, as at the nape of the neck, and moisture, as in theflexures, are important predisposing factors. Obesity, poorhygiene, widespread skin disease, immune deficiency anddiabetes mellitus may predispose in severe cases. Superficialfolliculitis can be non-infective; causes includecontact with oils and other irritant chemicals.Furuncles are tender red papules or nodules, whichbecome pustular centrally and often heal with some scarring.Furunculosis may be chronic, as in sycosis barbae, apustular eruption due to Staph. aureus that occurs on themale face. Carbuncles are often associated with fever andmalaise, and with an underlying systemic illness such asdiabetes or immune suppression.Follicular infections can produce bacteraemia and,rarely, bony and cerebral abscesses, and endocarditis.Swabs should be taken from pus and from the anteriornares, axilla and perineum of both the patient and householdcontacts (potential reservoirs of infection) in chroniccases.
Differential diagnosis The differential diagnosis includes dermatophyte infection(the fungi can be demonstrated by microscopy and cultureof hairs) and pseudofolliculitis, a non-infective papulopustularcondition on the face and neck caused by cut hairsgrowing back into the skin. The latter is very common inblack people because their hair is tightly curled. Acne vulgariscan usually be distinguished by the presenceof comedones, and the pustules are sterile.
Treatment Furuncles and carbuncles may need incision and drainage.Superficial staphylococcal folliculitis should respond to flucloxacillin(or an equivalent) for 1-2 weeks, but chronic cases may need treatment for longer, and treatment ofreservoir sites, e.g. chlorhexidine for the skin andmupirocin for the nose.
