DP10 Scalp disease in dermatomyositis
Authors: Aveen Connolly, Marianna Philippidou, Patrick Gordon, Chris Wincup, Fiona Worsnop, Daniel Creamer
Journal: British Journal of Dermatology (2024)

Abstract The clinical presentation of dermatomyositis (DM) is heterogeneous, with patients expressing varying degrees of muscle and skin inflammation. Scalp inflammation is often disregarded in the clinical assessment and is seldom the subject of clinical studies. However, DM at this site contributes significantly to the symptom burden, a feature heightened by the scalp’s comparative lack of response to standard immunosuppressant therapy. As well as a sparsity of studies detailing clinical features in scalp DM, the literature on scalp histopathology is also limited. In an attempt to define the range of clinicopathological features, and to consider potential associations with myositis-specific antibodies, we undertook a prospective observational study of scalp disease in a cohort of patients with DM. Over a 10-year period, 96 consecutive adult patients with clinically and immunologically proven DM were prospectively recruited. The extent of cutaneous DM was quantified using the Cutaneous Dermatomyositis Area and Severity Index (CDASI). For the purposes of our study, the scalp-CDASI was recorded separately. In patients with scalp DM, sites of involvement were recorded: frontal, parietal, occipital and vertex. The impact of cutaneous involvement was assessed using the Dermatology Life Quality Index and a scalp itch numerical rating score (NRS). In total, 47 of 96 patients with DM had scalp involvement, and all patients had cutaneous DM at other body sites. In the scalp DM cohort, scalp-CDASI ranged from 1/9 to 8/9. The distribution of DM involvement by scalp zone demonstrated 19 of 47 global, 17 of 47 occipitoparietal, and 11 of 47 frontovertex. The mean scalp itch NRS for the scalp DM group was 4.8, 33 of 47 patients reported scalp itching and/or soreness disturbing sleep, and 38 of 47 patients reported hair loss. In the scalp DM group, myositis-specific antibodies were demonstrated in 41 of 47 patients. Overall, 17 of 41 patients were positive for TIF-1g, 11 of 41 SAE, 6 of 41 MDA5, 3 of 41 Mi-2, 3 of 41 NXP-2, and 1 of 41 Jo-1. Assessment of scalp biopsies from nine patients demonstrated a number of dermatopathological features that appear exclusive to scalp DM. Unlike other scarring alopecias, there was no typical perifollicular fibroplasia, but in these cases, there was thickening of the basement membrane around the follicles. A further consistent observation involved the dermal collagen, which showed hyalinization, homogenization and areas of necrobiosis, as well as areas of very severe elastosis. Our findings suggest that the scalp possesses a site-specific susceptibility to DM inflammation, a hypothesis that mirrors the disease tropism seen in psoriasis, lupus and other inflammatory dermatoses. The evidence collected in this study has unequivocally demonstrated that scalp DM produces a symptom burden associated with considerable morbidity. Our study is the first to examine the subjective effects of scalp involvement in DM and to quantify its impact.