Background Background: Ataxia telangiectasia is one of the most common causes of autosomal recessive cerebellar ataxias. However, absence of telangiectasia, normal levels of alpha-fetoprotein and negative genetic test may direct to alternative diagnosis with similar phenotypes such as ataxia telangiectasia-like disorders (ATLD). Cases Cases: We report two instructive cases of ATLD: the first case with ataxia telangiectasia-like disorder type 1 related to MRE11A gene, and the second case with ataxia telangiectasia-like disorder type 2 related to PCNA gene. Literature Review Literature Review: ATLD is an unusual group of autosomal recessive diseases that share some clinical features and pathophysiological mechanisms with ataxia telangiectasia (AT). ATLD may be associated with mutations in the MRE11A (ATLD type 1) and PCNA (ATLD type 2) genes. ATLD belongs to the group of chromosomal instability syndromes. The reason for the term ATLD is related to the similar pathophysiological mechanisms observed in AT, which is characterized by chromosomal instability and radiosensitivity. Conclusions Conclusions: In this review, the main clinical features, biomarkers, brain imaging and genetics of ATLD are discussed. Mutations in the MRE11A and PCNA genes should be included in the differential diagnosis for early onset cerebellar ataxia with absence of telangiectasia and normal levels of alpha-fetoprotein.

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Spinocerebellar ataxias (SCAs) are a large group of genetically and phenotypically heterogeneous autosomal dominant, neurodegenerative disorders manifesting with progressive cerebellar ataxia usually with adult-onset.1 Currently, 48 subtypes of SCAs are described; of which, for 40 SCAs, the genes have been identified. The most frequent types are related to coding repeat expansions including SCA1, SCA2, SCA3, SCA6, and SCA7. However, for unusual SCA types, whole exome sequencing (WES) is necessary to identify the genetic cause. Late-onset cerebellar ataxia can be caused by several genetic mutations, but a large percentage of patients remain undiagnosed after WES.

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