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.