Fibrotic skin lesions in patients with localized scleroderma can cause muscle atrophy, disfigurement, and flexion contractures. There is no effective therapy for this disease. Skin fibrosis is thought to be caused by decreased collagenase activity. Collagenase activity can be induced in dermal fibroblasts by UVA₁ irradiation.

Our purpose was to assess whether UVA₁ radiation therapy is effective for patients with localized scleroderma.

Patients with localized scleroderma (n = 17) were exposed 30 times to 130 J/cm² UVA₁ (high-dose UVA₁ therapy; n = 10) or 20 J/cm2 UVA₁ (low-dose UVA₁ therapy; n = 7). Therapeutic effectiveness was assessed by evaluation of (1) clinical features, (2) thickness of sclerotic plaques, and (3) cutaneous elastometry. Sequential biopsy specimens from treated lesions were analyzed for collagenase I messenger RNA (mRNA) expression by semiquantitative reverse transcriptase-polymerase chain reaction.

In all patients, high-dose UVA₁ therapy softened sclerotic plaques, and complete clearance was observed in four of 10 patients. High-dose UVA₁ therapy significantly reduced thickness and increased elasticity of plaques. These changes could not be detected in unirradiated control plaques and were still present in 9 of 10 patients 3 months after cessation of therapy. For all factors assessed, high-dose UVA₁ was superior to low-dose UVA₁ therapy (p = 0.001). High-dose UVA₁ therapy increased collagenase I mRNA expression about 20-fold in treated plaques.

High-dose UVA₁ therapy is effective in the treatment of localized scleroderma. Effectiveness is UVA₁ dose dependent and is associated with induction of collagenase I expression.