Late-onset ataxia, may have episodic onset, downbeat nystagmus, vertigo, dysarthria, visual disturbances, and neuropathy^1,2. Involvement of the superior cerebellar peduncles is frequent and may aid in diagnostic efforts³. Cognitive impairment, including features of cerebellar cognitive-affective syndrome, has been reported and is correlated with ataxia severity in one cohort⁴.

Prevalence

Intermediate expansions 1-2% of population, but non-GAA-pure without relation to ataxia⁵. Found in multiple ethnicities⁶; diagnosed patients in America, Brazil, Japan, Germany, Spain, Canada, France, Austria, Australia, Italy, and Poland^5,7,8,9. Prevalence is population dependent, ranging from 1.83% to 61% of different ataxia cohorts, with specific enrichment in French-Canadian populations^10,11.

Age of Onset

Typical: 42-70; Range: 21-87^5,12.

HPO Terms

–

Association

MendelianRisk

Locus

hg19 chr13:102813924-102814076

hg38 chr13:102161574-102161726

t2t chr13:101377549-101377792

Details

Higher repeat size is associated with earlier age of onset¹². The 250-300 repeats range is linked to incomplete penetrance and >300 repeats with complete penetrance in some studies and resources^5,13,14. However, our thresholds are taken from suggestions made by Mohren et al upon evaluation of 169 cases and 802 controls; the authors propose lower thresholds based on pathogenic cases of shorter pure repeats¹⁴. Additionally, this study suggests that benign motifs may disrupt the formation of secondary structures in DNA/RNA, leading to reduced pathogenicity. The effects of interruptions on penetrance and onset have been demonstrated in patients, with uninterrupted expansions apparently necessary for disease¹⁵. Interruptions of GAG, GAAGGA, GAAGAAAGAA, GAAAAGAAGAAGGAAGAAGGAA, GAAAAGAAGAAGGAA, and GCAGAAGAAGAAGAA have been reported¹⁶. Variation in flanking regions appears to correlate with repeat size^14,17. Intermediate alleles may increase ataxia susceptibility in combination with other factors or be associated with a phenotypic spectrum (multiple system atrophy)^14,18. A complex (TTC/TGC) ≥300 repeat expansion has been associated as a risk factor for Parkinson's disease^19,20. Expansions can sometimes present as apparently sporadic adult-onset ataxia despite autosomal dominant inheritance²¹.

Mechanism

LoF

Reduced transcript 2¹⁰.

Detection

Short-read genome and exome sequencing are reported to be inaccurate in detecting these expansions [@genereviews:NBK599589]. Long-range PCR and bidirectional RP-PCR have been used for detection, while long-read sequencing has determined repeat structure and purity [@genereviews:NBK599589; @pmid:36516086]. Optical genome mapping detects full expansions (>200 repeats) but not premutation range alleles [@pmid:42293335 @pmid:39435674]

Year

2023²²

Location in Gene

Intron 1

Gene Strand

Alleles

Ref. Motif

GAA

Ranges

Benign (ref.)

AGG, CAG

Benign (gene)

CCT, CTG

Pathogenic (ref.)

AAG

Pathogenic (gene)

CTT

Unknown (ref.)

–

Unknown (gene)

–

Interruption (ref.)

AGG, AGAAGG, AAAGAAGAAG, AAGAAAAGAAGAAGGAAGAAGG, AAGAAAAGAAGAAGG, AAGAAGAAGAAGCAG

Interruption (gene)

CCT, CCTTCT, CTTCTTCTTT, CCTTCTTCCTTCTTCTTTTCTT, CCTTCTTCTTTTCTT, CTGCTTCTTCTTCTT

References

Direct supporting references for info on this page.

Repeat expansion disorders.

Zhongbo,Chen, Huw R,Morris, James,Polke, Nicholas W,Wood, Sonia,Gandhi, Mina,Ryten, Henry,Houlden, Arianna,Tucci

Practical neurology · 2025-05-15

pmid:39349043

Long-term response to aminopyridines in a cohort of patients with ataxia associated with downbeat nystagmus due to the FGF14 GAA expansion.

E,Muñoz, M,De la Cruz-Puebla, D,Pellerin, C,Painous, M I,Álvarez-Mora, M J,Dicaire, L,Rodríguez-Revenga, M C,Danzi, S,Zuchner, B,Brais

Neurologia · 2026-05-01

pmid:42044943

Involvement of the Superior Cerebellar Peduncles in GAA-

Shihan,Chen, Catherine,Ashton, Rawan,Sakalla, Guillemette,Clement, Sophie,Planel, Céline,Bonnet, Phillipa J,Lamont, Karthik,Kulanthaivelu, Atchayaram,Nalini, Henry,Houlden, Antoine,Duquette, Marie-Josée,Dicaire, Pablo,Iruzubieta Agudo, Javier,Ruiz-Martinez, Enrique,Marco De Lucas, Rodrigo,Sutil Berjon, Jon,Infante Ceberio, Elisabetta,Indelicato, Sylvia M,Boesch, Matthis,Synofzik, Benjamin,Bender, Matt C,Danzi, Stephan,Zuchner, David,Pellerin, Bernard,Brais, Mathilde,Renaud, Roberta,La Piana

Neurology. Genetics · 2025-02-21

pmid:39996128

Phenotype and Genetics of Spinocerebellar Ataxia Type 27B: Novel Movement-disorder Features, Cognitive Impairment, and Repeat Expansion Findings.

Ronak,Rashedi, Franca,Peemöller, Hannes,Erdmann, Mathias,Gelderblom, Ute,Hidding, Christos,Ganos, Robert,Chen, Angela,Abicht, Simone,Zittel

Cerebellum (London, England) · 2026-06-29

pmid:42371259

GAA-FGF14-Related Ataxia

David,Pellerin, Matt,Danzi, Mathilde,Renaud, Henry,Houlden, Matthis,Synofzik, Stephan,Zuchner, Bernard,Brais

GeneReviews® · 1993-01-01

genereviews:NBK599589

Neurological disorders caused by novel non-coding repeat expansions: clinical features and differential diagnosis.

Elisa,Vegezzi, Hiroyuki,Ishiura, D Cristopher,Bragg, David,Pellerin, Francesca,Magrinelli, Riccardo,Currò, Stefano,Facchini, Arianna,Tucci, John,Hardy, Nutan,Sharma, Matt C,Danzi, Stephan,Zuchner, Bernard,Brais, Mary M,Reilly, Shoji,Tsuji, Henry,Houlden, Andrea,Cortese

The Lancet. Neurology · 2024-07-01

pmid:38876750

Spinocerebellar ataxia 27B: a frequent and slowly progressive autosomal-dominant cerebellar ataxia-experience from an Italian cohort.

Sara,Satolli, Salvatore,Rossi, Elisa,Vegezzi, David,Pellerin, Maria Laura,Manca, Melissa,Barghigiani, Carla,Battisti, Giusi,Bilancieri, Giorgia,Bruno, Elena,Capacci, Carlo,Casali, Roberto,Ceravolo, Sirio,Cocozza, Stefano,Cotti Piccinelli, Chiara,Criscuolo, Matt C,Danzi, Rosa,De Micco, Giuseppe,De Michele, Marie-Josée,Dicaire, Grazia Maria Igea,Falcone, Roberto,Fancellu, Yasmine,Ferchichi, Camilla,Ferrari, Alessandro,Filla, Nicola,Fini, Alessandra,Govoni, Filomena,Lo Vecchio, Alessandro,Malandrini, Andrea,Mignarri, Olimpia,Musumeci, Claudia,Nesti, Sabina,Pappatà, Maria Teresa,Pellecchia, Alessia,Perna, Antonio,Petrucci, Maria Grazia,Pomponi, Roberta,Ravenni, Ivana,Ricca, Alessandra,Rufa, Elisabetta,Tabolacci, Alessandra,Tessa, Alessandro,Tessitore, Stephan,Zuchner, Gabriella,Silvestri, Andrea,Cortese, Bernard,Brais, Filippo M,Santorelli

Journal of neurology · 2024-06-17

pmid:38886208

An intronic GAA repeat expansion in FGF14 causes the autosomal-dominant adult-onset ataxia SCA27B/ATX-FGF14.

Haloom,Rafehi, Justin,Read, David J,Szmulewicz, Kayli C,Davies, Penny,Snell, Liam G,Fearnley, Liam,Scott, Mirja,Thomsen, Greta,Gillies, Kate,Pope, Mark F,Bennett, Jacob E,Munro, Kathie J,Ngo, Luke,Chen, Mathew J,Wallis, Ernest G,Butler, Kishore R,Kumar, Kathy Hc,Wu, Susan E,Tomlinson, Stephen,Tisch, Abhishek,Malhotra, Matthew,Lee-Archer, Egor,Dolzhenko, Michael A,Eberle, Leslie J,Roberts, Brent L,Fogel, Norbert,Brüggemann, Katja,Lohmann, Martin B,Delatycki, Melanie,Bahlo, Paul J,Lockhart

American journal of human genetics · 2023-06-01

pmid:37267898

Identification of FGF14 GAA Expansions in Polish Patients with Undiagnosed Cerebellar Ataxia - A Preliminary Study.

Marta,Matlawska, Karolina,Ziora-Jakutowicz, Marie-Josee,Dicaire, Joanna,Pera, David,Pellerin, Bernard,Brais, Pablo,Iruzubieta, Ewelina,Elert-Dobkowska, Anna,Sulek

Cerebellum (London, England) · 2026-05-07

pmid:42096001

Deep Intronic

David,Pellerin, Matt C,Danzi, Carlo,Wilke, Mathilde,Renaud, Sarah,Fazal, Marie-Josée,Dicaire, Carolin K,Scriba, Catherine,Ashton, Christopher,Yanick, Danique,Beijer, Adriana,Rebelo, Clarissa,Rocca, Zane,Jaunmuktane, Joshua A,Sonnen, Roxanne,Larivière, David,Genís, Laura,Molina Porcel, Karine,Choquet, Rawan,Sakalla, Sylvie,Provost, Rebecca,Robertson, Xavier,Allard-Chamard, Martine,Tétreault, Sarah J,Reiling, Sara,Nagy, Vikas,Nishadham, Meera,Purushottam, Seena,Vengalil, Mainak,Bardhan, Atchayaram,Nalini, Zhongbo,Chen, Jean,Mathieu, Rami,Massie, Colin H,Chalk, Anne-Louise,Lafontaine, François,Evoy, Marie-France,Rioux, Jiannis,Ragoussis, Kym M,Boycott, Marie-Pierre,Dubé, Antoine,Duquette, Henry,Houlden, Gianina,Ravenscroft, Nigel G,Laing, Phillipa J,Lamont, Mario A,Saporta, Rebecca,Schüle, Ludger,Schöls, Roberta,La Piana, Matthis,Synofzik, Stephan,Zuchner, Bernard,Brais

The New England journal of medicine · 2022-12-14

pmid:36516086

Challenges in the diagnosis of spinocerebellar ATAXIA 27B.

Núria Caballol,Pons, Alejandro Peral,Quirós, Anna,Planas-Ballvé, Paula Lombardo,Del Toro, Imma Hernan,Sendra, Asunción Ávila,Rivera

Journal of the neurological sciences · 2026-04-30

pmid:42090775

Clinical, Radiological and Pathological Features of a Large American Cohort of Spinocerebellar Ataxia (SCA27B).

Widad,Abou Chaar, Anirudh N,Eranki, Hannah A,Stevens, Sonya L,Watson, Darice Y,Wong, Veronica S,Avila, Megan,Delfeld, Alexander J,Gary, Sanjukta,Tawde, Malia,Triebold, Marcello,Cherchi, Tao,Xie, Paul J,Lockhart, Melanie,Bahlo, David,Pellerin, Marie-Josée,Dicaire, Matt,Danzi, Stephan,Zuchner, Bernard C,Brais, Susan,Perlman, Margit,Burmeister, Henry,Paulson, Sharan,Srinivasan, Lawrence,Schut, Matthew,Bower, Khalaf,Bushara, Chuanhong,Liao, Vikram G,Shakkottai, John,Collins, H Brent,Clark, Soma,Das, Brent L,Fogel, Christopher M,Gomez

Annals of neurology · 2024-09-12

pmid:39263992

Intronic

David,Pellerin, Carlo,Wilke, Andreas,Traschütz, Sara,Nagy, Riccardo,Currò, Marie-Josée,Dicaire, Hector,Garcia-Moreno, Mathieu,Anheim, Thomas,Wirth, Jennifer,Faber, Dagmar,Timmann, Christel,Depienne, Dan,Rujescu, José,Gazulla, Mary M,Reilly, Paola,Giunti, Bernard,Brais, Henry,Houlden, Ludger,Schöls, Michael,Strupp, Andrea,Cortese, Matthis,Synofzik

Journal of neurology, neurosurgery, and psychiatry · 2024-01-11

pmid:37399286

Identification and characterisation of pathogenic and non-pathogenic FGF14 repeat expansions.

Lars,Mohren, Friedrich,Erdlenbruch, Elsa,Leitão, Fabian,Kilpert, G Sebastian,Hönes, Sabine,Kaya, Christopher,Schröder, Andreas,Thieme, Marc,Sturm, Joohyun,Park, Agatha,Schlüter, Montserrat,Ruiz, Moisés,Morales de la Prida, Carlos,Casasnovas, Kerstin,Becker, Ulla,Roggenbuck, Sonali,Pechlivanis, Frank J,Kaiser, Matthis,Synofzik, Thomas,Wirth, Mathieu,Anheim, Tobias B,Haack, Paul J,Lockhart, Karl-Heinz,Jöckel, Aurora,Pujol, Stephan,Klebe, Dagmar,Timmann, Christel,Depienne

Nature communications · 2024-09-03

pmid:39227614

Targeted Long-Read Sequencing as a Single Assay Improves the Diagnosis of Spastic-Ataxia Disorders.

Laura Ivete,Rudaks, Igor,Stevanovski, Dennis,Yeow, Andre L M,Reis, Sanjog R,Chintalaphani, Pak Leng,Cheong, Hasindu,Gamaarachchi, Lisa,Worgan, Kate,Ahmad, Michael,Hayes, Andrew,Hannaford, Samuel,Kim, Victor S C,Fung, Gabor M,Halmagyi, Andrew,Martin, David,Manser, Michel,Tchan, Karl,Ng, Marina L,Kennerson, Ira W,Deveson, Kishore Raj,Kumar

Annals of clinical and translational neurology · 2025-02-25

pmid:40007153

FGF14 repeat length and mosaic interruptions: modifiers of spinocerebellar ataxia 27B?

Joshua,Laß, Mirja,Thomsen, Max,Borsche, Theresa,Lüth, Julia C,Prietzsche, Susen,Schaake, Andona,Milovanović, Hannah,Macpherson, Emil K,Gustavsson, Paula,Saffie Awad, Nataša,Dragašević-Mišković, Björn-Hergen,Laabs, Inke R,König, Ana,Westenberger, Christopher E,Pearson, Norbert,Brüggemann, Christine,Klein, Joanne,Trinh

Brain : a journal of neurology · 2025-11-04

pmid:40379261

A common flanking variant is associated with enhanced stability of the FGF14-SCA27B repeat locus.

David,Pellerin, Giulia F,Del Gobbo, Madeline,Couse, Egor,Dolzhenko, Sathiji K,Nageshwaran, Warren A,Cheung, Isaac R L,Xu, Marie-Josée,Dicaire, Guinevere,Spurdens, Gabriel,Matos-Rodrigues, Igor,Stevanovski, Carolin K,Scriba, Adriana,Rebelo, Virginie,Roth, Marion,Wandzel, Céline,Bonnet, Catherine,Ashton, Aman,Agarwal, Cyril,Peter, Dan,Hasson, Nadejda M,Tsankova, Ken,Dewar, Phillipa J,Lamont, Nigel G,Laing, Mathilde,Renaud, Henry,Houlden, Matthis,Synofzik, Karen,Usdin, Andre,Nussenzweig, Marek,Napierala, Zhao,Chen, Hong,Jiang, Ira W,Deveson, Gianina,Ravenscroft, Schahram,Akbarian, Michael A,Eberle, Kym M,Boycott, Tomi,Pastinen, Bernard,Brais, Stephan,Zuchner, Matt C,Danzi

Nature genetics · 2024-06-27

pmid:38937606

Frequency of FGF14 intronic GAA repeat expansion in patients with multiple system atrophy and undiagnosed ataxia in the Japanese population.

Toshiyuki,Kakumoto, Kenta,Orimo, Takashi,Matsukawa, Jun,Mitsui, Tomohiko,Ishihara, Osamu,Onodera, Yuta,Suzuki, Shinichi,Morishita, Tatsushi,Toda, Shoji,Tsuji

European journal of human genetics : EJHG · 2024-11-27

pmid:39604554

Long-read sequencing identifies FGF14 repeat expansions in Parkinson's disease.

Fulya,Akçimen, Kensuke,Daida, Lara M,Lange, Abraham,Moller, Abigail,Miano-Burkhardt, Laksh,Malik, Kimberly,Paquette, Pilar,Alvarez Jerez, Jackson,Mingle, Breeana,Baker, Melissa,Meredith, Cedric,Kouam, Paige,Jarreau, Androo,Markham, Jessica,Anderson, Miten,Jain, Mark,Chaisson, Mark,Cookson, Bradford,Casey, Hirotaka,Iwaki, Sara,Bandres-Ciga, Paula,Saffie-Awad, Mike A,Nalls, Zih-Hua,Fang, Andrew B,Singleton, Cornelis,Blauwendraat, Kimberley J,Billingsley

Brain : a journal of neurology · 2026-05-05

pmid:41327893

A Complex FGF14 (TTC)/(TGC) Repeat Expansion in Parkinson's Disease.

Xiaosheng,Zheng, Zhidong,Cen, Xinhui,Chen, Fan,Zhang, Chenxin,Ying, Nan,Jin, Peng,Liu, Yilin,Chen, Haotian,Wang, Jiaxiang,Li, Joanne,Trinh, Joshua,Laß, David,Pellerin, Matt C,Danzi, Stephan,Zuchner, Bernard,Brais, Shen-Yang,Lim, Ai Huey,Tan, Azlina,Ahmad-Annuar, Dehao,Yang, Lebo,Wang, Zhiru,Lin, Fei,Xie, Bo,Wang, Sheng,Wu, Zhiyuan,Ouyang, Piu,Chan, Shen,Hu, Christine,Klein, Hou-Feng,Zheng, Chaodong,Wang, Wei,Luo

Movement disorders : official journal of the Movement Disorder Society · 2025-11-24

pmid:41277530

GAA-FGF14 Ataxia Is a Frequently Overlooked Cause of Sporadic Adult-Onset Ataxia.

Eva-Maria,Kraus, Johannes,Lenz, Pauline,Ploettner, Patricia,Duffek, Jost-Julian,Rumpf, Rami Abou,Jamra, John,Wiedenhoeft, Denny,Popp

Clinical genetics · 2026-05-28

pmid:42204984

An intronic GAA repeat expansion in FGF14 causes the autosomal-dominant adult-onset ataxia SCA50/ATX-FGF14.

American journal of human genetics · 2022-12-08

pmid:36493768

Additional Literature

Additional literature related to this locus.

Raw PubMed search results
(All PubMed results returned by searching for this gene, tandem repeats, and disease, in medline format)

Phenotype and Genetics of Spinocerebellar Ataxia Type 27B: Novel Movement-disorder Features, Cognitive Impairment, and Repeat Expansion Findings.

Ronak,Rashedi, Franca,Peemöller, Hannes,Erdmann, Mathias,Gelderblom, Ute,Hidding, Christos,Ganos, Robert,Chen, Angela,Abicht, Simone,Zittel

Cerebellum (London, England) · 2026-06-29

pmid:42371259

Frequency and phenotype of GAA-FGF14 disease in bilateral vestibulopathy syndromes: insights from repeat expansion carriers, including a case of co-occurrence with RFC1-related CANVAS.

David,Pellerin, Felix,Heindl, Andreas,Traschütz, Pablo,Iruzubieta, Marie-Josée,Dicaire, Stephan,Zuchner, Annette M,Hartmann, Dan,Rujescu, Henry,Houlden, Bernard,Brais, Michael,Strupp, Matthis,Synofzik

Journal of neurology · 2026-05-25

pmid:42178418

SCA27B in Brazil: frequency, phenotype and genotype-phenotype correlations.

Amanda,de Jesus Araujo Dias, Cynthia,Silveira, Adriana Mendes,Vinagre, Luciana Cardoso,Bonadia, Nadson Bruno Serra,Santos, Thiago Junqueira R,Rezende, Luiza Alves,Corazza, José Luiz,Pedroso, Orlando Graziani P,Barsottini, Fabricio Diniz,de Lima, Marcondes C,França Junior

Journal of neurology · 2026-05-21

pmid:42168446

Expert commentary for "Episodic cerebellar ataxia mimicking stroke - diagnostic and therapeutic lessons from SCA27B".

Pablo,Iruzubieta, Bernard,Brais, David,Pellerin

Parkinsonism & related disorders · 2026-04-23

pmid:42055934

Pearls & Oy-sters: SCA27B as an Elusive Genetic Cause of Episodic Neurologic Symptoms in Later Adulthood.

Jacob,Yomtoob, Lucy,Morse, Ignacio Juan,Keller Sarmiento, Lisa,Kinsley, Christopher M,Gomez, Puneet,Opal, Niccolò Emanuele,Mencacci

Neurology · 2026-02-16

pmid:41698164

Clinical, Genetic, and Imaging Characteristics of SCA27B: Insights from a Large Dutch Cohort.

Teije H,van Prooije, Maartje,Pennings, Roderick P P W M,Maas, Jeroen,de Vries, Corien,Verschuuren-Bemelmans, Vincent,Odekerken, Sirwan K L,Darweesh, Mark,Huisman, Mayke,Oosterloo, Arthur,Buijink, Jaron,van de Wardt, Els,Vanhoutte, Tsz Hang,Wong, Lisette,Koens, Eva,de Boer, Judith,van Gaalen, Martijn,Beudel, Dareia S,Roos, Jorrit I,Hoff, Thimo,Cornelissen, Meyke,Schouten, Thatjana,Gardeichik, Erica,van der Looij, Christine,Klein, Joanne,Trinh, Erik-Jan,Kamsteeg, Bart,van de Warrenburg

Movement disorders : official journal of the Movement Disorder Society · 2026-01-08

pmid:41504274

First Report of Co-Occurring FGF14 (SCA27B) and RFC1 (CANVAS) Repeat Expansions in Two of Three Siblings with Late-Onset Cerebellar Ataxia.

Tasos,Tsokkos, Kyproula,Christodoulou, Christina,Votsi, Anthi,Georghiou, Andrea,Christofides, Astero,Constantinou, Eleni,Zamba-Papanicolaou

Cerebellum (London, England) · 2025-10-21

pmid:41118032

Clinical characteristics, cerebellar MR spectroscopy and response to 3,4-diaminopyridine in spinocerebellar ataxia 27B: the Sheffield Ataxia Centre experience.

Ikechukwu,Chukwuocha, David,Pellerin, Priya,Shanmugarajah, Theocharis,Tsironis, Emma,Foster, Nigel,Hoggard, Nick,Beauchamp, Lauren,Turton, Alisdair,McNeill, Bernard,Brais, Marios,Hadjivassiliou

Journal of neurology · 2025-10-09

pmid:41065930

Video head impulse test differentiates RFC1-CANVAS, FGF14-SCA27B, and idiopathic late-onset cerebellar ataxias.

Leonardo E,Ariello, Daniel R,Gold, Jennifer L,Millar, Michael C,Schubert, Weiyi,Mu, Liana,Rosenthal, David P W,Rastall

Journal of neurology · 2025-10-07

pmid:41055766

Locus SCA27B FGF14

Disease

Locus

Alleles

References

Additional Literature