Lately at the Foot and Ankle Institute, we have had a “rash” (pun intended) of patients presenting with erythrasma and/or pitted keratolysis. Let’s focus on pitted keratolysis.
Pitted keratolysis is a condition characterized by superficial erosions and 1 to 3 mm discrete crateriform pits along the sole of the foot due primarily to prolonged bromhidrosis.1 Although typically asymptomatic and non-inflammatory, patients with this condition often seek treatment because of the associated psychosocial factors such as odor and embarrassment.
The etiology of pitted keratolysis is attributed to a gram-positive bacterial infection. It could be Kytococcus sedentarius, Dermatophilus congolensis, Corynebacterium species or Streptomyces. With an increase in skin surface pH, prolonged occlusion and/or hyperhidrosis, the bacteria are allowed to proliferate and then produce proteinases, which create defects by destroying the stratum corneum.2 Then these defects gradually develop into the characteristic crater-like pits.
Where the skin is pitted, the area is generally flesh colored and macerated. This is a clinical diagnosis. One may use a Wood’s ultraviolet lamp but it rarely shows coral red fluorescence if Corynebacterium is present as it would for interdigital erythrasma. While this condition is typically asymptomatic, patients with symptoms usually complain of hyperhidrosis and malodor.
When it comes to the treatment of pitted keratolysis, studies have suggested several modalities such as salicylic acid, sulfur, clotrimazole (Lotrimin, Schering-Plough), antibacterial soaps, tetracyclines, neomycin, topical erythromycin, mupirocin (Bactroban, GlaxoSmithKline), imidazoles, systemic antibiotics and injectable botulinum toxin (Botox, Allergan).3,4 Other treatments include cotton socks, open footwear and proper hygiene.
My favorite treatment to use for this condition is an acne medication in an off-label manner. It is a combination of clindamycin and benzoyl peroxide otherwise known as Duac® (Stiefel Laboratories) and BenzaClin® (Valeant Dermatology). Certainly, one can use liquid formulations of clindamycin and erythromycin, but I prefer combination therapy when I am able to prescribe it.
Individually, clindamycin has both bactericidal and bacteriostatic activity and is effective against some protozoa, many anaerobes and aerobic gram-positive cocci.5 Furthermore, benzoyl peroxide has antibacterial, anti-keratolytic and comedolytic properties, and it works against both aerobic and anaerobic organisms. In the treatment of mild to moderate acne, researchers determined that the combined effect was significantly greater than their individual effects.6
Both compounds are antibacterial but the theory is that the keratolytic properties of benzoyl peroxide improve skin penetration of clindamycin. I have found that patients using either once daily Duac or twice daily BenzaClin on for pitted keratolysis do extremely well.
What do you like to use for pitted keratolysis?
1. Vlahovic T, Kemp K, Dunn SP. The use of a clindamycin 1%-benzoyl peroxide 5% topical gel in the treatment of pitted keratolysis: a novel therapy. Adv Skin Wound Care. 2009; 22(11):564.
2. Singh G, Naik C. Pitted keratolysis. Indian J Dermatol Venereol Leprol. 2005; 71(3):213-215.
3. Tamura B, Cuce L, Souza R, et al. Plantar hyperhydrosis and pitted keratolysis treated with botulinum toxin injection. Dermatol Surg. 2004; 30(12 Pt 2):1510-1514.
4. Khachemoune A, Janjua S. Pits on the soles of the feet. J Fam Med. 2005; 54(7):597-598.
5. Weingarten-Arams J, Adam HM. Clindamycin. Pediatr Rev. 2002; 23(4):149-150.
6. Weiss J, Shavin J, Davis M. Preliminary results of a non-randomized, multicenter, open label study of patient satisfaction after treatment with combination benzoyl peroxide/clindamycin topical gel for mild to moderate acne. Clin Ther. 2002; 24(10):1706-1717.
Editor’s note: The correct answer to the skin condition detailed in last month’s blog (http://bit.ly/ycUEg2  ) is atopic dermatitis.