The normal time it takes for the epidermis of the skin to renew itself is 28-30 days. In patients with psoriasis, this cycle can be compressed to as short as 3 days. The new cells that build up do not have time to shed, and the result is a thickened, scaly plaque with distinct borders separating it from the surrounding normal skin. When the scale is removed, the appearance of tiny droplets of blood on the plaque is called the “Auspitz sign”. Plaques are typically located on the elbows, knees, scalp, and the intergluteal cleft between the buttocks. However, psoriasis can occur anywhere on the skin surface. The prevalence of psoriasis in the general population is approximately 1 in 167 people.
Psoriasis can develop at any age, but it usually begins between age 15 and 35. Men and women are affected equally. No one knows for sure what causes it. More than one-third of patients with psoriasis have an immediate relative with the disease, which supports a genetic cause. Recent research points to an abnormality of the immune system’s T- cells as a culprit.
Psoriasis usually starts gradually, but sometimes it can have a sudden onset. The disease usually waxes and wanes. Flare- ups can be caused by trauma to the skin (Koebner’s phenomenon), emotional stress, and medications such as lithium, anti-malarial drugs, beta-blockers, and non-steroidal anti-inflammatory drugs (NSAIDs). About 1% of patients with AIDS develop very severe psoriasis, and in some cases psoriasis is the first sign of the disease. Patients often note that their psoriasis is better in the summer, perhaps due to a favorable effect from sunlight.
Nails can be involved in as many as 50% of patients with psoriasis. Pitting (small depressions on the nail plate) is the most common condition. Another condition, onycholysis, or separation of the nail plate from nail bed, can also occur. This happens when a psoriatic plaque forms in the nail bed, lifting and separating the overlying nail plate from the nail bed.
Variants of psoriasis include guttate and pustular types. Guttate, from the Latin for “spots that resemble drops”, is a rare variant (<2% of all psoriasis) that often follows a bout of streptococcal pharyngitis (“Strep throat”). The psoriasis appears as small, <1 cm scattered drop- like lesions. Pustular psoriasis can be limited to the palms and soles only (“palmoplantar pustulosis”) or can occur as a potentially life- threatening acute illness accompanied by fever and generalized weakness (von Zumbusch syndrome). Also, a condition called psoriatic arthritis occurs in 5% of patients and can cause joint pain especially in the hands and feet, or the hips and back.
There is no cure for psoriasis, but consistent treatment can decrease the build-up of scale and provide symptomatic relief. Treatment depends on several factors: the patient’s age, the type of psoriasis, the sites and extent of skin involvement, and associated medical disorders (like AIDS). The degree of psoriasis can range from mild to severe and is usually measured by percentage of total body involvement. Five topical agents are used: topical steroids, topical tar and anthralin preparations, calcipotriene (Vitamin D derivative), tazarotene (Vitamin A derivative), and ultraviolet B (UVB) light. Four systemic agents include: psoralen with Ultraviolet A light (PUVA), methotrexate, acitretin, and cyclosporine. Topical drugs affect the local area on which they are applied (i.e., the skin surface), while systemic drugs are usually either taken by mouth or injected and affect the entire body. Like many other skin diseases, psoriasis can be socially stigmatizing and can have devastating effects on self- esteem. The famous writer John Updike who was diagnosed with psoriasis at an early age, chronicles his struggles with the disease in his memoir, Self- Consciousness: “The name of the disease, spiritually speaking, is Humiliation.” However, after enrolling in a PUVA program, the writer watches with anticipation as his skin fights to suppress the disease--- and notes the changes that occur inside of him as well.
