[1] Leptogium kalbii was formally described as a new species in 2007 by Brazilian lichenologists Marcelo Marcelli and Iane P.R.

The type specimen was collected on a tree trunk in a shady restinga forest beside the Guaraú River in São Paulo.

The specific epithet honours German lichenologist Klaus Kalb, who, according to the authors, "has worked on Brazilian lichens for over 30 years, producing important contributions in tropical lichenology, and who sowed the seeds of modern lichenology in São Paulo State".

It has roughly spherical laminal structures the authors call "granules" that measure 0.1–0.25 mm in diameter, and originate from the edges of the wrinkles.

The cyanobacterial partner of Leptogium kalbii is Nostoc; their cells measure 5.0–6.5 by 5.0–6.5 μm.