Objective: To develop a diagnostic algorithm that allows to differentiate recessive or sporadic ataxias by the clinical phenotype, biochemical markers and neuroimaging studies of the patient.

Background: Ataxias are a heterogeneous group of neurodegenerative disorders that are mainly characterized by alterations in gait, speech, and movement coordination. Hereditary recessive ataxias represent a diagnostic challenge due to their phenotypic and genotypic heterogeneity.

Method: An observational, cross-sectional and ambispective study was carried out during the period from January 2019 to November 2020. To develop the early-onset recessive or sporadic ataxias algorithm (ALGOATAX), the clinical characteristics, biochemical and neurological markers, magnetic resonance imaging and other cabinet studies were analyzed. Based on the characteristics described above, the ataxias were classified into Friedreich’s ataxia, Friedreich’s-like ataxia, spastic paraparesis, mitochondrial cytopathies, and other innate errors of metabolism. The number of correct answers of the presumptive diagnosis was compared with the molecular diagnosis obtained by new generation sequencing, in order to obtain measures of frequency of entities and precision of the algorithm.

Results: One-hundred and twenty-nine patients with autosomal recessive cerebellar ataxias were studied with a mean age of onset of 21 ± 11.5 years. Friedreich’s ataxia was relatively rare in Mexico, as was alpha-tocopherol deficiency ataxia, which was not found in this series. Only one ataxia telangiectasia was diagnosed in the Friedreich’s-like ataxia group, probably due to baseline bias. The Friedreich-type ataxia group was the most difficult entity to diagnose by ALGOATAX. With the present algorithm, the premolecular diagnoses were correct in 83.8% of the cases respect to the definitive diagnoses. In the present study, entities never before described in Mexico were found as spastic ataxia Charlevoix- Saguenay, Perrault syndrome, SCAR10, cerebrotendinous xanthomatosis, among others. 

Conclusion: The algorithm is capable of diagnosing more than 80% of autosomal recessive cerebellar ataxias before molecular diagnosis in the current state. 

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MDS Abstracts - https://www.mdsabstracts.org/abstract/diagnostic-algorithm-in-recessive-and-sporadic-early-onset-ataxias/