Objective: To highlight the possibility of ataxia developing as the primary symptom of Leber hereditary optic neuropathy (LHON).

Background: LHON is a mitochondrial disorder characterized by bilateral loss of central vision. In a number of cases of LHON, involvement of the nervous system has been reported, a condition termed LHON plus. We present a case of a patient with LHON whose primary symptom was ataxia.

Method: A 17-year-old male presented with severe unsteadiness when walking, slurred speech, and episodes of aggressive behavior. The family includes three other children; the mother and all siblings have visual impairment. The unsteadiness in the proband first appeared at the age of 12 and progressively worsened. At the age of 14, he developed swallowing difficulties and his gait deteriorated. Neurological examination revealed memory impairment, learning difficulties, dysarthria, restricted horizontal eye movements, diplopia, horizontal nystagmus, pseudobulbar syndrome, distal limb weakness (4/5), hypotonia, diminished deep tendon reflexes and ataxic gait. Romberg test, and coordination tests showed past pointing and intention tremor.

Results: Brain MRI showed atrophy of the brainstem, cerebellar vermis, and hemispheres. Screening for common mutations in the ATXN1, ATXN2, and ATXN3 genes was negative. Ophthalmological examination: hypermetropia in both eyes. Blood lactate was elevated at 3.83 mmol/L. The patient’s siblings underwent examinations; all of them were diagnosed with optic nerve atrophy. Considering the family history, mitochondrial genome sequencing was performed on the patient, revealing the homoplasmic variant m.14484T>C in the MT-ND6 gene. A diagnosis of LHON-plus was made. Using Sanger sequencing, the mutation was confirmed in the proband, his siblings, and his mother.

At the age of 17, the proband had no visual disturbances; optic nerve atrophy was only revealed three years later at age 20. Follow-up was conducted for 5 years: the proband lost the ability to walk independently at age 19, but other family members did not develop neurological symptoms, retaining only visual impairments.

Conclusion: This report underscores the necessity of considering LHON among possible diagnoses in cases presenting primarily with ataxia and emphasizes the significance of obtaining a detailed familial medical history.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/ataxia-as-the-primary-symptom-of-leber-hereditary-optic-neuropathy-a-case-report-of-a-patient-and-family-observation/