BI15: Widespread pediculosis pubis infestation associated with natalizumab

R. Gandhi, C. Fernandez, A. Kelly and J. Natkunarajah

Kingston Hospital NHS Foundation Trust, London, UK

A 50-year-old man presented to the dermatology clinic with an 8-week history of a new widespread eruption, predominantly affecting his chest, arms and legs. Four months prior, he had presented with a red, scaly rash bilaterally and was diagnosed with psoriasis, for which he was started on Enstilar® foam, which successfully maintained his psoriasis. He had a background of multiple sclerosis (MS), for which he was on natalizumab (Tysabri), pregabalin, zopiclone and baclofen. His last natalizumab infusion was 3 months earlier. On examination, he had scattered erythematous plaques with follicular crusting. Dermoscopy showed haemorrhagic vessels with pubic crabs attached to hair shafts and multiple eggs attached to the hair strands. He was diagnosed with a widespread pediculosis pubis infestation and was commenced on Lyclear dermal cream, Epaderm ointment and ivermectin 15 mg. Two months later his pediculosis pubis infestation had cleared and his psoriasis remained well maintained on the Enlister foam. Pediculosis is an infestation of lice on the body, head or the public region (Coates SJ, Thomas C, Chosidow O et al. Ectoparasites: pediculosis and tungiasis. J Am Acad Dermatol 2020; 82: 551–69). The most common symptom of presentation is pruritis; however, patients who are immunocompromised may also present with a vesicular, pustular or nodular rash (Flinders DC, Schweinitz PD. Pediculosis and scabies. Am Fam Physician 2004; 69: 341–8). We present a case of a widespread pediculosis pubis infestation secondary to immunosuppression with natalizumab treatment for MS, which was successfully treated by ivermectin and Lyclear.