A double-blind study of superficial radiotherapy in psoriatic nail dystrophy.

In a double-blind controlled study, superficial radiotherapy (SRT) was given to psoriatic fingernails as three fractionated doses of 150 cGy (90 kV, 5 mA, 1.00 mm aluminium filter). The treated nails demonstrated a significant fall in scoring on a clinical rating scale 10 and 15 weeks after therapy (mean scores = 4.4 and 4.6 respectively) when compared with a mean pretreatment score of 5.5 at week 0 (p less than 0.0001 and p less than 0.05 respectively); the treated nails also showed significant clinical improvement when compared with the sham-treated nails at weeks 10 and 15 (p less than 0.05). Mean nail thickness in treated nails 15 weeks after therapy was significantly thinner (mean thickness = 0.75 mm) than that of sham-treated nails (0.88 mm, p = 0.005), but the difference was not significant at week 20. The rate of linear nail growth was unaffected. SRT appears to confer a definite albeit temporary benefit on psoriasis of the nails at this dosage.