Pitted and ringed keratolysis (keratolysis plantare sulcatum)

Management Strategy

Most patients experience little or mild irritation. Maceration, foul odor, and soreness are the main reasons for consultation. Hyperhidrosis, sweat retention, prolonged occlusion, immersion, and increases in the skin pH appear to be important causes of PK. Industrial workers wearing rubber shoes or soldiers whose feet are continually occluded or wet are at high risk of developing this infection. Initial management strategies should therefore include instruction on foot hygiene and avoidance of occlusive footwear.

Treatment involves use of topical or systemic antimicrobial agents and/or reduction of the hyperhidrosis.

The availability of some topical antibiotic products has been restricted to variable degrees in different countries in order to reduce the occurrence of antimicrobial resistance, so not all formulations discussed here are universally available.

The topical antibiotic most commonly used by the authors is fusidic acid, which can be prescribed as 2% fusidic acid cream or ointment three to four times daily. Topical 1% clindamycin, benzoyl peroxide, 1% clindamycin with 5% benzoyl peroxide gel, 2%–4% erythromycin, mupirocin, and gentamicin sulfate have been reported to be effective. Although 1% clindamycin hydrochloride can be made up with 660 mg dissolved in 55 mL of 70% isopropyl alcohol and 5% propylene glycol, we suggest that Dalacin T topical solution or Duac gel may be used instead. This can be applied two or three times daily. Erythromycin 2% cream or ointment has been reported to be effective if used twice daily. Japanese dermatologists have had some success in treating PK with gentamicin sulfate cream. Mupirocin 2% ointment may be administered two to three times daily; PK has also responded to topical antifungals such as clotrimazole and miconazole; 1% clotrimazole cream or 2% miconazole cream or ointment may be applied twice daily. Topical antiseptics, such as 4% chlorhexidine scrub, can be effective.

Systemic antibiotics can be reserved for severe and resistant cases. A 7-day course of oral erythromycin at 250 mg four times a day is usually well tolerated. The use of penicillin or sulfonamides does not seem to be effective. Antibiotic resistance has been reported with Micrococcus sedentarius to penicillin, methicillin, ampicillin, oxacillin, and erythromycin.

Topical 20% aluminum chloride hexahydrate, available as Driclor or Anhydrol Forte, may reduce hyperhidrosis and odor, but the pits remain. The solution is applied at night, allowed to dry, and washed off the following day. Initially it should be used daily until the condition is brought under control, when it can be used less frequently. The use of 20% aluminum chloride hexahydrate for palmoplantar hyperhidrosis has not been as successful as its use for axillary hyperhidrosis.

Topical 4% formaldehyde solution applied with gauze soaks as the patient sits or stands with their feet on the gauze in a bowl for 10–15 min once or twice daily reduces the hyperhidrosis. Alternatively, immersion of the soles in 5% formaldehyde may be utilized. Formalin ointment 40% has been used with some success but is not commercially available in the UK.

Iontophoresis is frequently used in palmar and plantar hyperhidrosis and can be used in the treatment of PK. Botulinum toxin has also been used. Oral anticholinergics are perhaps excessive.