Protomyces helminthiae Maire, 1914
Parts of the midrib and main side veins are swollen, often also with red or yellow tones. Here the fungus forms spores in the leaf, in or near the vascular bundles.
Klenke & Scholler consider helminthiae an invalid synonym of P. picridis. But even if the synonymy is correct (the Index Fungorum, 2015, treats both as valid species), helminthiae is the oldest and therefore probably valid name.
Buhr (1965a), Klenke & Scholler (2015a).