Objective: To describe an unusual case of ataxia-telangiectasia (A-T) presenting with myoclonic tremor and cervical dystonia in the absence of ataxia.

Background: A-T is a rare autosomal recessive disorder caused by pathogenic variants in ATM, characterized by childhood-onset cerebellar ataxia, oculomotor apraxia, telangiectasias, immunodeficiency, and elevated alpha-fetoprotein (AFP) [1,2]. Predominant movement disorder presentations in variant A-T are uncommon and likely underrecognized, particularly in the absence of ataxia [3,4].

Method: We report the case of a 43-year-old woman with tremor onset in childhood and a previous diagnosis of essential tremor.

Results: Symptoms started at age 9 with left-hand tremor and progressed slowly, later involving the neck, right arm, legs, and voice. She was evaluated at age 43. Medical history included type 2 diabetes mellitus, and no cancer history. Examination showed cervical dystonia with right torticollis and retrocollis, head and mild voice tremor, fine tremor of the eyelids, jaw, and tongue, marked bilateral postural-action tremor, and multifocal irregular action myoclonus, predominantly on the left. There was no bradykinesia, rigidity, pyramidal syndrome, gait ataxia, or oculomotor apraxia. No cutaneous telangiectasias were found, but subtle conjunctival telangiectasias were present [Figure 1]. Brain MRI was reported as normal; however, we suspected telangiectatic changes in the globus pallidus [Figure 2]. Dopamine transporter imaging was not suggestive of nigrostriatal degeneration. AFP was markedly elevated (110.8 ng/mL). A dystonia and myoclonic tremor gene panel was negative. Expanded genetic testing identified compound heterozygous ATM variants: c.5497-2A>C, classified as pathogenic, and c.7429G>A (p.Gly2477Arg), currently classified as a variant of uncertain significance. These findings supported the diagnosis of variant A-T with predominant movement disorder phenotype.

Conclusion: This report highlights an exceptionally rare presentation of A-T in which myoclonic tremor and cervical dystonia predominated over the expected ataxic phenotype, underscoring the broad phenotypic heterogeneity of the disorder. It also suggests that serum AFP may be a valuable diagnostic clue and may merit broader consideration in the work-up of unexplained movement disorders, especially with childhood onset.

Figure 1

Figure 2

References: [1] Riboldi GM, Samanta D, Asuncion RMD, Frucht S. Ataxia-telangiectasia. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan–. Updated 2024 Mar 6. PMID: 30137827.
[2] Collyer J, Rajan DS. Ataxia telangiectasia. Semin Pediatr Neurol. 2024;52:101169. doi:10.1016/j.spen.2024.101169. PMID: 39622612.
[3] Teive HAG, Camargo CHF, Munhoz RP. More than ataxia—movement disorders in ataxia-telangiectasia. Parkinsonism Relat Disord. 2018;46:3-8. doi:10.1016/j.parkreldis.2017.12.009.
[4] Tiet MY, Horvath R, Hensiek AE. Ataxia telangiectasia: what the neurologist needs to know. Pract Neurol. 2020;20(5):404-414. doi:10.1136/practneurol-2019-002253.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/myoclonic-tremor-and-cervical-dystonia-as-an-atypical-presentation-of-ataxia-telangiectasia/