Primary familial brain calcification[1] (PFBC), also known as familial idiopathic basal ganglia calcification (FIBGC) and Fahr's disease,[1] is a rare,[2]genetically dominant or recessive, inherited neurological disorder characterized by abnormal deposits of calcium in areas of the brain that control movement. Through the use of CT scans, calcifications are seen primarily in the basal ganglia and in other areas such as the cerebral cortex.[3]
Symptoms of this disease include deterioration of motor functions and speech, seizures, and other involuntary movement. Other symptoms are headaches, dementia, and vision impairment. Characteristics of Parkinson's Disease are also similar to PFBC.[4]
The disease usually manifests itself in the third to fifth decade of life but may appear in childhood or later in life.[5] It usually presents with clumsiness, fatigability, unsteady gait, slow or slurred speech, difficulty swallowing, involuntary movements or muscle cramping. Seizures of various types are common. Neuropsychiatric symptoms, which may be the first or the most prominent manifestations, range from mild difficulty with concentration and memory to changes in personality and/or behavior, to psychosis and dementia.[6]
Causes
This condition can be inherited in an autosomal dominant or recessive fashion. Several genes have been associated with this condition.[citation needed]
Mutation
A locus at 14q has been suggested, but no gene has been identified.[7] A second locus has been identified on chromosome 8[8] and a third has been reported on chromosome 2.[9] This suggests there may be some genetic heterogeneity in this disease.[10]
A mutation in the gene encoding the type III sodium dependent phosphate transporter 2 (SLC20A2) located on chromosome 8 has been reported.[11] Biochemical evidence suggests that phosphate transport may be involved in this disease.[citation needed]
Two other genes have been associated with this condition: PDGFB on chromosome 22 and PDGFRB on chromosome 5.[12] These genes are biochemically linked: PDGFRB encodes the platelet-derived growth factor receptor β and PDGFB encodes the ligand of PDGF-Rβ. These genes are active during angiogenesis to recruit pericytes which suggests that alterations in the blood brain barrier may be involved in the pathogenesis of this condition.[citation needed]
A fourth gene associated with this condition is XPR1. This gene is the long arm of located on chromosome 1 (1q25.3).[citation needed]
Another gene that has been associated with this condition is MYORG.[13][14] This gene is located on the long arm of chromosome 9 (9p13.3). This gene is associated with an autosomal recessive inheritance pattern in this condition.[citation needed]
Another gene junctional adhesion molecule 2 (JAM2) has been associated with an autosomal recessive form of this condition.[15]
The most recently found gene to be associated with PFBC is Nα-acetyltransferase 60 (NAA60).[16] NAA60 is a protein belonging to the family of N-terminal acetyltransferases (NATs), which catalyze the transfer of an acetyl group from acetyl-coenzyme A (Ac-CoA) to the N-terminus of proteins.[17] NAA60 is specifically localized to the Golgi apparatus and can acetylate membrane proteins post-translationally that have cytosolic N-termini starting with methionine followed by hydrophobic- or amphipathic-type amino acids (ML-, MI-, MF-, MY-, and MK-).[18][19][20]
Calcification seems to be progressive, since calcifications are generally more extensive in older individuals and an increase in calcification can sometimes be documented on follow up of affected subjects.[citation needed]
As well as the usual sites the cerebellar gyri, brain stem, centrum semiovale and subcortical white matter may also be affected. Diffuse atrophic changes with dilatation of the subarachnoid space and/or ventricular system may coexist with the calcifications. Histologically concentric calcium deposits within the walls of small and medium-sized arteries are present. Less frequently the veins may also be affected. Droplet calcifications can be observed along capillaries. These deposits may eventually lead to closure of the lumina of vessels.[citation needed]
The pallidal deposits stain positively for iron. Diffuse gliosis may surround the large deposits but significant loss of nerve cells is rare. On electron microscopy the mineral deposits appear as amorphous or crystalline material surrounded by a basal membrane. Calcium granules are seen within the cytoplasm of neuronal and glial cells. The calcifications seen in this condition are indistinguishable from those secondary to hypoparathyroidism or other causes.[citation needed]
Brain CT scan is the preferred method of localizing and assessing the extent of cerebral calcifications.[citation needed]
Elevated levels of copper, iron, magnesium and zinc but not calcium have been reported in the CSF but the significance of this finding—if any—is not known.[23]
The diagnosis requires the following criteria be met:[citation needed]
the presence of bilateral calcification of the basal ganglia
the presence of progressive neurologic dysfunction
the absence of an alternative metabolic, infectious, toxic or traumatic cause
a family history consistent with autosomal dominant inheritance
The calcification is usually identified on CT scan but may be visible on plain films of the skull.[citation needed]
Differential diagnosis
Basal ganglia calcification may occur as a consequence of several other known genetic conditions and these have to be excluded before a diagnosis can be made.[24][25][26][27]
Management
There is currently no cure for PFBC nor a standard course of treatment. The available treatment is directed symptomatic control. If parkinsonian features develop, there is generally poor response to levodopa therapy. Case reports have suggested that haloperidol or lithium carbonate may help with psychotic symptoms.[28] One case report described an improvement with the use of a bisphosphonate.[29]
Prognosis
The prognosis for any individual with PFBC is variable and hard to predict. There is no reliable correlation between age, extent of calcium deposits in the brain, and neurological deficit. Since the appearance of calcification is age-dependent, a CT scan could be negative in a gene carrier who is younger than the age of 55.[30]
Progressive neurological deterioration generally results in disability and death.[citation needed]
↑ Dai X, Gao Y, Xu Z, etal. (October 2010). "Identification of a novel genetic locus on chromosome 8p21.1-q11.23 for idiopathic basal ganglia calcification". Am. J. Med. Genet. B Neuropsychiatr. Genet. 153B (7): 1305–10. doi:10.1002/ajmg.b.31102. PMID20552677. S2CID21165897.
↑ Volpato CB, De Grandi A, Buffone E, etal. (November 2009). "2q37 as a susceptibility locus for idiopathic basal ganglia calcification (IBGC) in a large South Tyrolean family". J. Mol. Neurosci. 39 (3): 346–53. doi:10.1007/s12031-009-9287-3. PMID19757205. S2CID23235853.
↑ Wang C, Li Y, Shi L, etal. (March 2012). "Mutations in SLC20A2 link familial idiopathic basal ganglia calcification with phosphate homeostasis". Nat. Genet. 44 (3): 254–6. doi:10.1038/ng.1077. PMID22327515. S2CID2515200.
↑ Westenberger A1, Klein C (2014) The genetics of primary familial brain calcifications. Curr Neurol Neurosci Rep 14(10):490 doi: 10.1007/s11910-014-0490-4
↑ Arkadir D, Lossos A, Rahat D, Abu Snineh M, Schueler-Furman O, Nitschke S, Minassian BA, Sadaka Y, Lerer I, Tabach Y, Meiner V (2018) MYORG is associated with recessive primary familial brain calcification. Ann Clin Transl Neurol 6(1):106-113
↑ Yao XP, Cheng X, Wang C, Zhao M, Guo XX, Su HZ, Lai LL, Zou XH, Chen XJ, Zhao Y, Dong EL, Lu YQ, Wu S, Li X, Fan G, Yu H, Xu J, Wang N, Xiong ZQ, Chen WJ (2018) Biallelic Mutations in MYORG cause autosomal recessive primary familial brain calcification. Neuron 98(6):1116-1123
↑ Cen Z, Chen Y, Chen S, Wang H, Yang D, Zhang H, Wu H, Wang L, Tang S, Ye J, Shen J, Wang H, Fu F, Chen X, Xie F, Liu P, Xu X, Cao J, Cai P, Pan Q1,12, Li J, Yang W, Shan PF, Li Y, Liu JY, Zhang B, Luo W (2019) Biallelic loss-of-function mutations in JAM2 cause primary familial brain calcification. Brain
↑ Bonazza S, La Morgia C, Martinelli P, Capellari S (August 2011). "Strio-pallido-dentate calcinosis: a diagnostic approach in adult patients". Neurol. Sci. 32 (4): 537–45. doi:10.1007/s10072-011-0514-7. PMID21479613. S2CID11316462.
↑ Morita M, Tsuge I, Matsuoka H, etal. (May 1998). "Calcification in the basal ganglia with chronic active Epstein-Barr virus infection". Neurology. 50 (5): 1485–8. doi:10.1212/wnl.50.5.1485. PMID9596016. S2CID7376355.
↑ Preusser M, Kitzwoegerer M, Budka H, Brugger S (October 2007). "Bilateral striopallidodentate calcification (Fahr's syndrome) and multiple system atrophy in a patient with longstanding hypoparathyroidism". Neuropathology. 27 (5): 453–6. doi:10.1111/j.1440-1789.2007.00790.x. PMID18018479. S2CID34345069.
↑ Tojyo K, Hattori T, Sekijima Y, Yoshida K, Ikeda S (June 2001). "[A case of idiopathic brain calcification associated with dyschromatosis symmetrica hereditaria, aplasia of dental root, and aortic valve sclerosis]". Rinsho Shinkeigaku (in Japanese). 41 (6): 299–305. PMID11771159.
↑ Munir KM (February 1986). "The treatment of psychotic symptoms in Fahr's disease with lithium carbonate". J Clin Psychopharmacol. 6 (1): 36–8. doi:10.1097/00004714-198602000-00008. PMID3081601.
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