Multimodal PET Findings in MYORG-Related Primary familial Brain Calcification Caused by a Novel Homozygous Frameshift Mutation.

Primary familial brain calcification (PFBC) is a rare inherited neurological disorder characterized by bilateral intracranial calcifications and heterogeneous clinical manifestations. MYORG-related PFBC is a recently identified autosomal recessive subtype; however, its metabolic abnormalities and dopaminergic function remain incompletely characterized. We report a 45-year-old man with progressive parkinsonism, dysarthria, and a history of recurrent limb twitching. Genetic analysis identified a novel homozygous frameshift variant in MYORG (c.348_352dup, p.Gly118AlafsTer76), confirming the diagnosis of MYORG-related PFBC. Multimodal positron emission tomography (PET), including fluorine-18 fluorodeoxyglucose (18F-FDG) PET and fluorine-18 fluoropropyl-carbomethoxy iodophenyl tropane (18F-FP-CIT) PET, was performed to assess cerebral glucose metabolism and presynaptic dopaminergic function. 18F-FDG PET demonstrated reduced metabolism in the right caudate nucleus and cerebellum, whereas 18F-FP-CIT PET showed preserved striatal dopamine transporter availability. These findings suggest that parkinsonian symptoms in this patient with MYORG-related PFBC may be associated with dysfunction of the striato-cerebellar pathways rather than presynaptic nigrostriatal degeneration. This case expands the genetic spectrum of MYORG-related PFBC and highlights the potential value of combined metabolic and dopaminergic PET imaging for evaluating movement disorders associated with PFBC.