The invention in one embodiment is directed to solid forms of {S-3-(4-Amino-1-oxo-isoindolin-2-yl)(piperidine-3,4,4,5,5-d5)-2,6-dione}, including an anhydrous crystalline form, two hydrates, and an amorphous form. The invention in one embodiment is directed to methods of preparation of the solid forms.