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Fahr syndrome, also known as primary Familial Brain Calcification is a rare, genetically heterogeneous neurodegenerative condition characterized by bilateral symmetrical intracranial calcifications, primarily affecting the basal ganglia and other brain regions, usually in the absence of secondary metabolic causes.

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Classification

Type	Etiology
Primary	Idiopathic/Familial Fahr Disease:
• Autosomal dominant (most common): Mutations in SLC20A2, PDGFRB, PDGFB, XPR1, MYORG
• Presents typically between 3rd–5th decade
• Often asymptomatic early; penetrance increases with age
Secondary	Secondary to systemic/metabolic disorders:
• Hypoparathyroidism (most common)
• Pseudohypoparathyroidism
• Hyperparathyroidism
• Mitochondrial diseases
• Infectious causes (e.g., CMV, toxoplasmosis)
• Toxins (e.g., lead poisoning, carbon monoxide)

Clinical features

Symptoms often correlate poorly with the extent of calcification.

Domain	Common Manifestations
Extrapyramidal	Parkinsonism, chorea, dystonia, tremor
Cognitive	Dementia, psychosis, behavioral changes
Seizures	Partial or generalized
Pyramidal signs	Spasticity, weakness
Speech & Gait	Dysarthria, ataxia, balance disturbances

Diagnosis

Diagnostic workup:

Non-contrast CT head
Serum calcium, phosphate, PTH, magnesium
Vitamin D levels
Genetic testing (if familial form suspected)
Rule out secondary causes before labeling as idiopathic Fahr disease

Radiology

Modality	Imaging feature
CT	• ****Bilateral symmetric calcifications
MR	• Early stages: Normal
• Late stages: Low T2/FLAIR signal & SWI/GRE susceptibility
PET/SPECT	• ****Reduced metabolism

Characteristic locations: