Thallus forming small patches, 3-7 mm, sometimes crusts up to 15 mm across on the saxicolous thallus of Lecidea paupercula, areolate, esorediate; hypothallus indistinct. Areolae flat to slightly concave, smooth, glabrous, yellowish brown to blackish brown, 0.2-0.7 (-1.2) mm across, 0.1-0.4 mm thick. Each areola surrounded by a 0.1-0.2 mm broad, black margin formed by a rather loose thallospore forming tissue of bluish black, warty, 7-9 µm thick hyphae. Thallospores (1-)2-3-celled, with irregularly arranged rounded, warty, bluish black cells. Photobiont: unicellular, green algae, 4-11 µm diam. Apothecia very rare (seen only in one collection from Sweden: Jamtland, R. Santesson no. 26469), adnate, in the middle of areolae, 0.4-0.5 mm diam., margin thin, not prominent. Excipulum brown, pseudoparenchymatous. Hymenium hyaline, 60-75 µm high. Paraphyses simple or with few branches, thick, conglutinate, apices slightly thickened. Asci clavate with an I+ blue wall and tholus, 8-spored. Spores simple, ellipsoid, thin-walled, smooth, 8-11 X 5-7 µm. Pycnidia not seen.
Chemistry: thallus C-, K-, Pd-; stictic, norstictic and cryptostictic acid.
L. leproloma is known from more than 40 localities in Sweden (Hrj to TL) and Norway (AAg, Hrd, MRo, Nrd, Trs and Fnm) and from Greenland (Disco, comm. E. Steen Hansen), always found on Lecidea paupercula, mainly on vertical acidic rocks in alpine and subalpine areas.-R.S.