Diascopy is very helpful in the diagnosis of –
Diascopy is of particular value in detecting granulomatous nodules, which have a translucent brownish colour known as 'apple jelly' nodules, e.g. in lupus vulgaris. In Naevus anaemic, localized vasoconstriction, other pigments are unaltered - diascopy of adjacent skin, therefore, reveals an identical colour to that of the depigmented area.
By contrast, diascopy of skin adjacent to vitiligo, in which there is a loss of melanin, demonstrates that the vitiligo remains paler. Application of medium pressure to a spider naevus can compress radiating arterioles and allow visualization of pulsatile flow in the feeding vessel. Palpable purpuric lesions that do not blanch on pressure (diascopy) suggest vasculitis.
Cutaneous vasculitis
Nevus anaemicus
Lupus vulgaris
All of the above