Psoriasis.

Psoriasis is a common, chronic, immune-mediated skin disease affecting more than 40 million individuals worldwide. Psoriasis, along with psoriatic arthritis, are part of a broader psoriatic disease spectrum, and present with inflammatory skin and musculoskeletal manifestations driven by shared genetic, environmental, and immunological mechanisms. Skin psoriasis presents with diverse clinical phenotypes, including chronic plaque psoriasis, guttate, palmoplantar, erythrodermic, and pustular forms. Beyond cutaneous manifestations, psoriasis is associated with a substantial psychosocial burden and a wide range of comorbidities, including mental health disorders and cardio-metabolic diseases. Key psoriasis risk factors include genetic polymorphisms (most notably HLA-C*06:02), obesity, and environmental factors such as trauma, infections, and specific medications. Advances in understanding the key role of the IL-23-IL-17 inflammatory axis and related immunogenetic pathways have redefined psoriasis as a complex immune disorder, leading to the development of highly effective targeted biologic and small-molecule therapies that modulate cytokine signalling and intracellular pathways, offering improved disease control across cutaneous and musculoskeletal domains.