5-methyltetrahydrofolate 5-metiltetrahidrofolato B12 vitamin Defectos del folato cerebral Enfermedades metabólicas hereditarias Exome sequencing Inherited metabolic diseases Lactic acid Primary lactic acidosis Secuenciación exómica acidosis láctica primaria aciduria metilmalónica cerebral folate defects deficiencia deficiency diagnóstico diferencial diagnóstico molecular differential diagnosis epilepsia epilepsy errores innatos del metabolismo homocistinúria homocystinuria inborn errors of metabolism metabolism metabolismo methylmalonic aciduria molecular diagnosis vitamina B12