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Rod bipolar cell dysfunction in POLG retinopathy.

Kit Green Sanderson¹, Eoghan Millar², Anupreet Tumber²

¹Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Canada.

Documenta Ophthalmologica. Advances in Ophthalmology

|June 23, 2020

Summary

This summary is machine-generated.

This study details a child with POLG-related SANDO, highlighting novel electrophysiological findings. An electronegative ERG, indicating rod ON-bipolar dysfunction, was observed for the first time in this disorder.

Keywords:

Electroretinography Light signal transduction POLG POLG1 Polymerase gamma Retinal bipolar cells

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Area of Science:

Neurogenetics
Ophthalmology
Electrophysiology

Background:

Mitochondrial DNA polymerase gamma (POLG) mutations cause a spectrum of neurological disorders.
Sensory ataxic neuropathy, dysarthria, and ophthalmoparesis (SANDO) is a rare POLG-related disorder.
Understanding genotype-phenotype correlations is crucial for diagnosis and management.

Observation:

A pediatric patient with a homozygous POLG mutation (c.911T>G/p.Leu304Arg) presented with SANDO features including seizures, hypotonia, and ophthalmoplegia.
Ophthalmological evaluation revealed reduced visual acuity and bilateral ptosis.
Serial electroretinography (ERG) demonstrated a markedly reduced b/a ratio and an electronegative configuration in dark-adapted responses.

Findings:

This is the first report of an electronegative ERG in a POLG-related disorder.
The electronegative ERG suggests generalized rod ON-bipolar cell dysfunction.
Clinical features aligned with SANDO but showed overlap with other POLG-related conditions.

Implications:

The novel ERG finding provides insights into the pathophysiology of POLG-related disorders.
This case underscores the broad phenotypic variability associated with POLG mutations.
Electrophysiological studies, particularly ERG, can aid in diagnosing and characterizing POLG-related neurological conditions.