Actually, everyone that said Hypopigmentation is correct. The single gene Lesser, that we are discussing, has a reduction in display of all pigments. Reduced pigment = Hypopigmentation. And the superform is Hypopigmentation taken to the extreme of Apigmentation which is phenotypically expressed as Leucism.
We would need a genetic-level interrogation to validate this gene as being the same as Isabelline, but behaviourally they are similar