This is not an independent disease, but is frequently of considerable importance as a part of the phenomena of other conditions. It affects the finer vessels of certain organs, and consists, like atheroma, in a thickening of the internal coat (see Fig. 247) which, in these fine arteries, frequently leads to complete.obliteration. This form of lesion is seen especially in interstitial inflammations of organs, and is particularly frequent in chronic interstitial nephritis. where'it will be again referred to.