Psoriasis is a complex, chronic, immune-mediated inflammatory disease. While characterized by raised, scaly plaques on the skin, the underlying process involves a dysfunctional immune system that triggers inflammation throughout the body. This makes psoriasis a systemic condition, connecting the skin disease to various other health issues, known as comorbidities. Recognizing this systemic nature is fundamental to comprehensive management, as the chronic inflammatory state affects the musculoskeletal, cardiovascular, and other internal systems.
Beyond the Skin: The Musculoskeletal System
Psoriatic Arthritis (PsA) is the most recognized internal manifestation, affecting up to 30% of individuals with skin psoriasis. PsA is an inflammatory arthritis that targets the joints, connective tissues, and spine. If left untreated, this condition often leads to progressive structural damage and functional loss. PsA shares the same immune pathway as skin lesions, driven by the overactivity of the interleukin-23/interleukin-17 (IL-23/IL-17) signaling cascade.
The inflammation presents in distinct ways beyond typical joint swelling. A characteristic feature is enthesitis, which is the painful inflammation where tendons or ligaments attach directly to the bone, often in the heels or elbows. Another presentation is dactylitis, or “sausage digits,” which is the diffuse swelling of an entire finger or toe.
In some individuals, the inflammatory process focuses on the spine, known as psoriatic spondylitis. This causes stiffness and pain, particularly in the lower back and neck. While skin psoriasis usually precedes joint symptoms, the arthritis can sometimes appear first or concurrently. Treatments targeting specific inflammatory cytokines, such as IL-17 inhibitors, are effective for both the skin and joint disease. Early detection and management of PsA are important to prevent rapid bone erosion.
Systemic Inflammation and Cardiovascular Risk
The chronic systemic inflammation associated with psoriasis significantly impacts the cardiovascular system, increasing the risk of serious heart-related events. Inflammatory mediators such as Tumor Necrosis Factor-alpha (TNF-α) and Interleukin-17 (IL-17) circulate throughout the body, directly contributing to accelerated atherosclerosis. This process involves fatty plaques building up inside arteries, causing them to narrow and harden faster in patients with moderate to severe psoriasis.
This accelerated arterial damage increases the likelihood of heart attack, stroke, and chronic heart failure. The inflammation disrupts the normal function of the endothelium, the inner lining of blood vessels, promoting plaque instability and blood clot formation. Cardiovascular disease is a leading cause of reduced life expectancy in this population.
Psoriasis is also strongly interconnected with Metabolic Syndrome, a cluster of conditions including abdominal obesity, hypertension, elevated blood sugar, and abnormal cholesterol levels. Inflammatory cytokines interfere with insulin signaling, promoting insulin resistance that often precedes Type 2 Diabetes. This metabolic dysfunction can occur even in patients who are not overweight.
Adipokines, hormones released by fat tissue, also play a role in exacerbating both the inflammatory and metabolic risks. The combination of chronic systemic inflammation and metabolic dysregulation compounds the danger to the heart and vascular system.
Secondary Effects on Other Internal Systems
The chronic inflammatory nature of psoriasis affects several other internal organs, leading to a range of secondary conditions. The liver is a common target, with an elevated prevalence of Non-Alcoholic Fatty Liver Disease (NAFLD). NAFLD, characterized by fat accumulation in liver cells, is often considered the hepatic manifestation of the metabolic syndrome linked to psoriasis.
Persistent inflammation and insulin resistance contribute to the progression of NAFLD to Non-Alcoholic Steatohepatitis (NASH). NASH is a more severe, inflammatory form that can lead to liver fibrosis and cirrhosis. Psoriasis patients have approximately twice the risk of developing NAFLD compared to the general population, emphasizing the need for regular liver function monitoring.
The inflammatory process also connects psoriasis to the gastrointestinal tract, specifically Inflammatory Bowel Disease (IBD), which includes Crohn’s disease and Ulcerative Colitis. Psoriasis and IBD share common genetic markers and overlapping immune pathways. The prevalence of IBD is notably higher in people with psoriasis, suggesting a shared susceptibility to chronic inflammation in both the skin and the gut lining.
The eyes can also be affected by systemic inflammation, with uveitis being the most significant ocular complication. Uveitis is the inflammation of the uvea, the middle layer of the eye, which can cause pain, redness, and light sensitivity. If not addressed, uveitis can potentially lead to permanent vision loss.