THIN CORPUS CALLOSUM:  Hypoxanthine guanine phosphoribosyltransferase deficiency  Creatine transporter deficiency  Gaucher disease  Molybdenum cofactor deficiency  Aromatic L-amino acid decarboxylase deficiency  ABSENT/HYPOPLASIA CORPUS CALLOSUM:  Glycine encephalopathy due to aminomethyltransferase deficiency  Pyruvate dehydrogenase complex deficiency  Zellweger spectrum disorders  Pyridoxine-dependent epilepsy. The gene discussed is AMT; the disease is creatine transporter deficiency.