Charcot-Marie-Tooth disease type 4J and autosomal recessive spinocerebellar ataxia type 20 in a girl: coexistence of two rare disorders

Abstract

Charcot-Marie-Tooth disease type 4J (CMT4J) and autosomal recessive spinocerebellar ataxia type 20 (SCAR20) are rare autosomal recessive disorders that, to our knowledge, have not been previously reported in the Latin American population.

Objective: To present the case of a patient of Chilean descent with a dual clinical and genetic diagnosis of CMT4J and SCAR20.

Clinical Case: The patient was born to healthy consanguineous parents with congenital hypotonia and a swallowing disorder. At 2 years of age, dystonia, areflexia, predominantly distal muscle weakness, and sensorineural hearing loss were observed. Additional tests revealed demyelinating polyneuropathy and cerebellar atrophy. At the last evaluation (6 years), she had a coarse facial appearance, did not speak, could sit independently, but was unable to walk. A whole-exome sequencing (WES) identified a homozygous pathogenic variant in FIG4 and another likely pathogenic variant in SNX14, establishing a dual diagnosis of CMT4J and SCAR20. The patient’s symptoms overlapped with those of patients with CMT4J and SCAR20.

Conclusions: This case underscores the importance of performing adequate phenotypic characterization before ordering WES, especially in cases with nonspecific or combined clinical presentations, in order to obtain an accurate genetic diagnosis and provide personalized medical care.