Supplementary Material for: How scalp trichoscopy aids in the diagnosis of psoriasis in the setting of psoriatic arthritis - case report

Psoriasis is a chronic, immune-mediated skin disease that affects approximately 125 million people worldwide. Psoriatic arthritis (PsA), a complex chronic inflammatory arthritis, is classified as part of the spondyloarthritis spectrum, along with primary ankylosing spondylitis, reactive arthritis, arthritis associated with inflammatory bowel disease, and undifferentiated spondyloarthritis.
We report two cases of patients with arthropathy who were referred by rheumatologist. Thorough physical examination of the skin and nails revealed no psoriatic changes. However, despite the absence of scalp-related complaints, a diagnosis of psoriasis was established based on trichoscopic findings.
Cases in which patients with PsA have even mild cutaneous psoriatic lesions are common, making the diagnosis easier. The two cases described above highlight the role of trichoscopy and emphasize the importance of collaboration between dermatologists and rheumatologists. When rheumatologists investigate possible causes of arthritis and consider PsA as a differential diagnosis, referring the patient to a dermatologist is important. On the other hand, in cases of scalp psoriasis, if arthropathy is present, the patient should consult rheumatologist to determine whether joint involvement is caused by another rheumatologic condition. In clinical practice, scalp psoriasis is frequently observed as an independent condition, and its presence does not exclude the possibility of other coexisting pathologies.

银屑病（Psoriasis）是一种慢性免疫介导性皮肤病，全球约有1.25亿人受累。银屑病关节炎（Psoriatic arthritis, PsA）是一种复杂的慢性炎性关节炎，归类为脊柱关节炎（spondyloarthritis）谱系的一部分，与原发性强直性脊柱炎、反应性关节炎、炎性肠病相关性关节炎以及未分化脊柱关节炎同属该谱系。
本文报告2例由风湿病科医师转诊的关节病患者。经全面的皮肤及指甲体格检查，未发现银屑病样皮损改变。尽管患者无头皮相关不适症状，但基于毛发镜（trichoscopy）检查结果，最终确诊为银屑病。
银屑病关节炎患者仅存在轻度皮肤银屑病皮损的情况较为常见，这使得诊断更为容易。上述两则病例凸显了毛发镜的应用价值，并强调了皮肤科与风湿病科医师协作的重要性。当风湿病科医师排查关节炎的潜在病因并将银屑病关节炎纳入鉴别诊断时，将患者转诊至皮肤科医师处至关重要。反之，若头皮银屑病患者伴有关节病，则应就诊于风湿病科医师，以明确关节受累是否由其他风湿性疾病所致。临床实践中，头皮银屑病常作为独立疾病被发现，其存在并不排除合并其他病理状态的可能。