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Correspondence to Dr Nitin Sahi, Queen Square Multiple Sclerosis Centre, Department of Neuroinflammation, UCL Queen Square Institute of Neurology, University College London, London, UK; [email protected]
Case 1
A 54-year-old woman developed periungual digital warts. She had relapsing–remitting multiple sclerosis (MS) and had taken fingolimod since 2018. She had previously switched from natalizumab, due to John Cunningham (JC) virus seropositivity, and had relapsed on interferon beta-1a. Although her warts persisted despite topical salicylic acid, she wished to continue fingolimod (figure 1A).
Case 2
A 54-year-old woman with relapsing–remitting MS started fingolimod in 2014, following relapse on interferon beta-1a. She developed digital warts in 2016, which became widespread despite salicylic acid and cryotherapy. The warts improved following a dose reduction in 2019 but have persisted (figure 1B).
Cutaneous warts are caused by the human papilloma virus (HPV).1 2 Their prevalence varies markedly, but is highest during childhood (~5%–30%) and falls significantly after the second decade of life.1 2 Salicylic acid or cryotherapy are the most evidence-based treatments with cure rates around 50%, but there are many treatments available and spontaneous resolution is common.1 However, in immunocompromised people, warts are often refractory to standard treatments1 with significant psychosocial impact.3
These cases highlight the previously reported problem of treatment-refractory warts in patients taking fingolimod for MS.4–6 We retrospectively identified warts in 7 out of 336 patients (2.1%) receiving fingolimod at our centre between 2011 and 2019. Fingolimod treatment was modified in four patients. Two patients stopped fingolimod with either improvement or resolution, although one subsequently relapsed. Two patients were given a reduced dose; the warts improved in both, but one patient relapsed and restarted full dosing. Three patients did not change treatment and their treatment-refractory warts continued. The warts were unlikely to improve without either stopping or reducing the drug, with risk of...