BH22 Alopecia areata caused by an adverse reaction to denosumab

Abstract A 67-year-old woman with a background of osteoporosis and hypercholesterolaemia on treatment with denosumab and simvastatin presented with a 9-month history of patchy hair loss. Initially, the patient put this down to simvastatin as this was commenced around the time the hair loss started. However, the hair loss persisted on cessation of the statin. Treatment with denosumab had commenced 7 months prior to her hair loss. There was no personal or family history of autoimmune disease or hair loss. Blood tests including thyroid function tests and haematinic screening were normal. There was no itching or soreness of the scalp and she had not noticed any visible rashes or scaling. On examination, there were areas of nonscarring hair loss on the scalp with evidence of exclamation-mark hairs. There was no perifollicular erythema or scaling. Some of her hair had turned white. Clinically this was in keeping with alopecia areata. The patient stopped her denosumab injections and has been treated twice with intralesional triamcinolone injections (5–10 mg mL−1). She is now having good regrowth of her hair. Denosumab is a human monoclonal antibody that was approved by the National Institute for Health and Care Excellence and the US Food and Drug Administration for the prevention of osteoporotic fractures in postmenopausal women in 2010. Alopecia areata and other autoimmune reactions have been seen with other biologic drugs, including dupilumab (interleukin-14 and interleukin-3 inhibitor) and anti-tumour necrosis factor (TNF)-α medications. A review article in the Journal of the American Academy of Dermatology found that 76% of cases of drug-induced alopecia areata were felt to be due to monoclonal antibodies [Alhanshali L, Buontempo M, Shapiro J, Lo Sicco K. Medication-induced hair loss: an update. J Am Acad Dermatol 2023; 89 (2 Suppl.): S20–8]. It is possible that denosumab, a TNF cytokine that binds to and inhibits RANK/RANKL, can cause similar reactions to other members of the TNF drug class (Lyakhovitsky A, Oshinsky S, Gilboa S, Barzilai A. Alopecia areata after denosumab treatment for osteoporosis. JAAD Case Rep 2016; 2: 298–300). The mechanism by which denosumab can trigger alopecia areata is not completely understood and is likely multifactorial. Based on the timeline, it was unlikely that simvastatin had triggered the process. This case is one of only a handful of reports of denosumab inducing alopecia areata and it is important to consider this as a cause in patients taking this medication.