This name is a synonym of Rhododendron chamaethomsonii var. chamaethauma (Tagg) Cowan & Davidian.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 12305003) with original publication details: Sp. Rhodod. 514 1930.
This name was in version 1 of The Plant List, record tro-12305003, and has not been changed.