The transcapillary escape rate of albumin (TERnIb) i.e., the fraction of intravascular albumin, that passes to the extravascular space per unit time is a parameter of the leakage of macromolecules from the total microvasculature . In this study TERnn, was m easured b efore and after PUV A treatment to psoriatic patients to study functional alterations in the microvasculature induced by the treatment. Short-term PUV A treatment caused a statistically significant increase in TERnl" in 7 out of 8

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... atients (p < 0.05). This seems to b e a functional equivalent to the morphological changes in the dermal capillary of psoriatic skin and the ultrastructural changes in the dermal vessel walls d escribe d after PUV A treatment. It suggests, that the amorphous p erivascular masses described in the p soriatic skin after PUV A treatment might be plasmatic substances deposite d in and around the vessel wall as a result of increased vascular permeability. In the psoriatic skin t h ere are ab normally lar ge end oth elial gaps in th e veno us capilla ri es and venules [1 ,2], and in a case of severe pustular psoriasis with hypoalbuminae mia it was suggested, t h at albumin was being lost t hrough t his leaky vasculature [3], In the light of t hese ul t rastructural ch a nges functional alteration of t h e escape rate of plasma proteins from the m icrovascul ature of th e psoriatic skin could be expected . T h e transcap illal'y escape rate of albumin (TER"II') i.e., the fra ction of intravascular mass of albumin, that passes to the extravascular space per unit t ime is a parameter of the leakage to macromolecul es in the microvasculature [4, 5] . TERulh is increased in patients with extensive sk in diseases and in burns [5, 6] . In a group of patients with uncom plicated psoriasis we found normal escape rates [7] . However, it must be stressed , that t h e TER"lb is a measure of t h e overall whole-body escape r ate of a lbumin from t h e microvasculature. Increased leakage fro m t h e vessels of the psoriatic plaques may t h er efore not be able to cause a m easurable increase in the TER"II,. Followin g single exposure to t h e normal skin of relatively large doses of longwave ultraviolet ligh t (UV A, 320 to 400 nm) , Kumakiri, Hashimoto, a nd Willis [8] found pronounced dermal damage with widely open endoth elia l gaps in the superfi cial dermal vessels. Considerin g t h e ultrastructural ch a n ges in t h e psoriatic s kin a nd th e effect of UV A on t h e dermis, it h as been the purpose of this study to examine, wh ethe r treatm ent with psoralen fo llowed by UV A (PUV A) could al ter the overall TER"II, in patients with ps'ori asis. MATERIALS AND M ETHODS Fi ve ma le and 3 female patients with at least 30% of the skin affected by psoria is vu lgaris were examined (Table n. None of the patients had