From a review on Cerebral Folate Deficiency:
A disorder initially reported as folinic acid responsive epilepsy was subsequently shown to be allelic with PDE – both are caused by biallelic mutations in ALDH7A1 (Gallagher et al, 2009).
Does it mean that the same exact mutation causes both diseases, and they are fully identical? I think it means that, but I'm not 100% sure, so I decided to ask here.
Since by allele we mean "a variant form of a given gene" this must be the term to indicate that two diseases previously considered different are in fact fully identical.