FOLH1 and Pelizeaus-Merzbacher spectrum disorder: During PET/CT follow-up two months after the last therapy, seven patients (38.9%) were classified as having progressive disease (PD) or progressive metabolic disease (PMD) (new lesions and increasing PSMA expression in lesions), 3 patients (16.7%) were assessed as stable disease (SD)/stable metabolic disease (SMD), and 4 patients (22.2%) were evaluated as partial response (PR)/partial metabolic response (PMR).