Essential Insights On Treating Psoriatic Lesions In The Lower Extremity

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Author(s): 
M. Joel Morse, DPM

   Pustular psoriasis. This is an uncommon form of psoriasis and presents as studded with tiny, superficial, sterile pustular lesions. There are two forms of pustular psoriasis: localized and generalized. In the localized form, the disease is confined to hands and feet, and tends to be chronic.19 The usual bacterial organism in the blood of pustular psoriasis is Staphylococcus aureus. High dosages of oral corticosteroids for a period of time are among the more common precipitating factors. One may see pustular psoriasis of the nail unit, known as acrodermatitis continua, which starts as pustules under the nail and can result in extensive destruction of the nail plate.20

   Palmoplantar psoriasis. Also uncommon, this disabling condition significantly impairs quality of life due to the fact that it can limit the use of one’s hand to do work and can cause significant pain with walking. Although palm and sole psoriasis affects a small (less than 5 percent) portion of the total cutaneous surface, the impact of palm and sole psoriasis on quality of life is out of proportion to the small percent of body surface area affected.21

   The physical examination can show erythematous scaly patches and fissured hyperkeratotic psoriatic plaques of both the palmar and plantar surfaces. The differential for pustular psoriasis includes: chronic eczema, reactive arthritis (Reiter’s syndrome), paraneoplastic acrokeratosis and superficial fungal infection.

   Nail psoriasis. Nail involvement is common in psoriasis and can be the initial and only site of involvement in some patients. The morphology of nail changes depends on whether the nail matrix, nail bed or hyponychium has been affected. Nail involvement is more common in those who have concurrent psoriatic arthritis. Bedi noted nail changes in 74 percent of patients with plaque or palmoplantar psoriasis while isolated nail affliction occurred in 6 percent of cases.17 Various nail changes observed in descending order of frequency were pitting, nail plate thickening, partial onycholysis, subungual hyperkeratosis, yellow-brown discoloration, paronychia and complete onycholysis.22

   Changes in the nail matrix include: pitting, leukonychia (white patches under the nails), red spots in the lunula and nail plate crumbling. Within the nail bed, we see onycholysis, splinter hemorrhage, oil spot or oil drop patches (salmon or pink colored blotches on the surface of the nail) and hyperkeratosis.13 The oil-drop sign is virtually pathognomonic for psoriasis.23 Other changes include onychauxis, Beau’s lines and transverse depressions.

   In psoriatic arthritis, an inflammatory reaction results in microtrauma to the joints and the entheses. Research has shown the nail to be functionally integrated with entheses associated with the distal phalanx that provides anchorage to the skin and joint.24

   The finding of nail disease in the patient increases the possibility of the patient having psoriatic arthritis. Many studies have shown that 10 to 20 percent of those with psoriasis will get psoriatic arthritis.25 The same inflammatory changes, namely T-cell proliferation, that affect the skin can affect the joints. Among the most common joints affected are the hands and feet (distal interphalangeal joints), and the spine.26 Psoriatic arthritis can affect virtually any joint of the body, producing a wide variety of arthritic changes and joint deformity. Psoriatic arthritis can destroy joints, similar to rheumatoid arthritis.

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