Doughnut wart - an unwanted complication

This blog reports a case study of an 11-year-old girl with an unusual complication of cryotherapy for a wart on her leg.

Case: An 11-year-old girl with doughnut wart on her ankle

Case Report

A healthy 11-year-old girl presented to the podiatry clinic with a two-year history of cutaneous warts. Lesions were located on her right thumb, on the plantar surfaces of both feet (3rd/4th metatarsophalangeal area) and her right anterior ankle.

Initially she had tried various over the counter remedies including salicylic acid treatment. After little success she had consulted her general practitioner who had attempted four rounds of painful cryotherapy. Due to lack of response following three treatments, the practitioner undertook a fourth treatment using a longer freeze thaw cycle than previous which the patient reported as being extremely painful.

Following treatment, the lesion on the anterior leg blistered and subsequently developed a secondary bacterial infection. As the ankle lesion healed, clearance was noted centrally however, the area enlarged into a larger annular lesion with a raised verrucous edge (figure 1).

Diagnosis: Doughnut Wart

Discussion

The doughnut wart (also known as a ring wart) is an unusual, and rarely reported, phenomenon occurring in warts and verrucae, an American study highlighted just one case occurring in one patient out of 366 treated hand warts [1].

Following a treatment, the lesion typically undergoes central resolution, but viral recurrence occurs at the periphery often a few millimetres away from the original lesion creating a “doughnut ring” pattern (see figure 2 and 3).

Of the handful of cases reported, most arise following destructive treatments such as cantharidin [1-4], cryotherapy [5, 6], lasers [7] and salicylic acid [7, 8]. In 1958, Epstein and Kligman [3] discuss the first documented case occurring following application of the blistering agent Cantharidin onto the forearm of a 17-year-old girl.

Figure 2: Doughnut warts in a 7 year old following salicylic acid treatment [8]

(Reprinted under the Creative Commons Licence)

Figure 3 : Dermoscopy of the patient in figure two showing central clearing of the lesions [8]

(Reprinted under the Creative Commons Licence)

What causes doughnut warts?

The exact mechanism is unclear although Yoo et al., [6] suggest it is a process of autoinoculation of the wart virus which spreads to the periphery of the blister cavity causing lesion development at the margins in a previously uninfected area. This can be described as the Koebner phenomenon (see my previous blog) whereby trauma to a previously unaffected area of skin can lead to development of the disease in that space. Warts are known to “pseudo-koebnerize” [9] – physical trauma can lead to seeding of the viral particles into previously uninfected skin. Chemical action can have a similar effect. Alternatively, an explanation is that clearance of the wart, without a suitable margin could lead to activation of latent virus in the periphery of the lesion [7].

How are they treated?

There is a lot we don’t know about doughnut warts. Firstly, can you continue to treat them as before, using the same therapy which potentially caused them without further harm? There is no real answer in the literature to guide clinicians.

One study by Nofal, documents 15 cases treated with immunotherapy (candida antigen injections). Their particular rationale for the selection of treatment was that they wanted to avoid further spread choosing an immunomodulatory rather than destructive treatments. Moreover, suggesting destructive techniques fail to induce significant immunity to prevent future recurrence.  

In our case, the clinician has taken a similar approach, the patient has subsequently undergone a course of microwave treatment which has demonstrated immunomodulatory activity [10]. Currently, all her hand and plantar lesions have cleared rapidly after initial treatment, and the treatment continues for her ankle lesion.

Authors Statement: 

Dean Cronkwright is a podiatrist at The Australian Wart Clinic in Victoria, Australia

Patient and parental permission was sought and full consent was given for publication on this website.

References

1.           Rosenberg, E.W., R.A. Amonette, and J.H. Gardner, Cantharidin Treatment of Warts at Home. Archives of Dermatology, 1977. 113(8): p. 1134-1134.

2.           Hood, C.R., Jr. and J.R. Miller, The Ring Verruca Plantaris in Cantharidin Use (A Case Report). J Am Podiatr Med Assoc, 2018. 108(2): p. 189-193.

3.           Epstein, W.L. and A.M. Kligman, Treatment of warts with cantharidin. AMA Arch Derm, 1958. 77(5): p. 508-11.

4.           Findlay, G.H., Wart Relapses at the Edges of Therapeutic Cantharidin Blisters. A.M.A. Archives of Dermatology, 1959. 80(5): p. 589-590.

5.           Han, F. and B. Guo, An annular plaque on the hand. BMJ, 2020. 370: p. m2209.

6.           Yoo, K., et al., Two Cases of Doughnut-shaped Warts Following Cryosurgery. Korean J Dermatol, 2008. 46(12): p. 1651-1653.

7.           Nofal, A., et al., Successful treatment of doughnut warts with intralesional Candida antigen immunotherapy. Journal of Cosmetic Dermatology, 2021. 20(1): p. 295-299.

8.           Sethy, M., et al., Doughnut Wart Following Salicylic Acid Application: A Rare Case Report. Indian Dermatol Online J, 2021. 12(3): p. 451-453.

9.           Rubin, A.I. and M.J. Stiller, A listing of skin conditions exhibiting the koebner and pseudo-koebner phenomena with eliciting stimuli. J Cutan Med Surg, 2002. 6(1): p. 29-34.

10.        Ardern-Jones, M., et al., Induction of antihuman papillomavirus immunity by microwave treatment of skin. British Journal of Dermatology, 2016. 175(Supp 1): p. 151.