Abstract
We read with interest the article by Al Bandari et al about a 20-month-old boy with Leber’s hereditary optic neuropathy (LHON) due to the homoplasmic variant m.11778G>A, who was identified during a newborn hearing screening and showed mild-to-moderate bilateral sensorineural hearing loss (SNHL) in several auditory brainstem response tests. 1 The patient’s 5-year-old sister, who was also a carrier of the m.11778G>A variant, also had hearing impairment, but her medical history included several episodes of otitis media. 1 The index patient was treated with coenzyme Q. 1 The study is noteworthy, but some points require discussion.
The first point is that we disagree with the statement in the introduction that hearing impairment is rare in LHON. 1 In a study of 48 patients with LHON carrying the mtDNA11778, mtDNA14484, mtDNA14482, and mtDNA3460 variants, more than 25% of participants showed electrophysiological signs of auditory neuropathy with absent or severely delayed auditory brainstem potentials. 2 Auditory perception was abnormal in both symptomatic and asymptomatic subjects, with >20% of cases showing impaired recognition of auditory temporal (timing) cues and >30% showing abnormal speech perception both in quiet environments and in the presence of background noise. 2 It was concluded that a relatively high proportion of LHON patients suffer from hearing difficulties due to impairment of central auditory pathways. 2
The second point is that a second genetic cause for the hearing impairment cannot be completely ruled out. 1 Although the patient underwent panel testing for mutations in genes that are frequently mutated in patients with hearing impairment, it remains possible that the index patient carried a mutation in a gene that has not yet been described. Therefore, it might be useful to perform whole-exome or genome sequencing.
The third point is that the index patient should be diagnosed with LHON plus rather than LHON, as he also suffered from hearing loss and a patent foramen ovale. 1 In this context, there is no explanation as to why the patient was not prospectively examined for multisystem involvement. Although the cerebral MRI was described as normal, we should know whether magnetic resonance spectroscopy showed elevated lactate levels in the brain.
The fourth point is that cardiac involvement in LHON may be more severe than described in the index article. 1 In a study of 73 LHON patients, 23.2% had cardiac abnormalities. 3 Patients may not only have a patent foramen ovale, but also preexcitation syndrome, AV block, bundle branch block, noncompaction, or repolarization abnormalities.3,4 Therefore, LHON patients also have an increased risk of sudden cardiac death and should be monitored accordingly.
The fifth point is that there was no report on the response to treatment with coenzyme Q. 1 Did the SNHL improve with treatment with coenzyme Q? LHON patients often benefit from idebenone in terms of their visual impairment. 5 Why was the patient treated with coenzyme Q instead of idebenone?
Overall, hearing impairment is not uncommon in LHON. LHON patients should be prospectively examined for multisystem involvement; cardiac involvement is common, and LHON patients should be treated with idebenone.
