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Presentation type	E-poster
Title	Beyond mitochondrial DNA: a POLG-related LHON phenotype

Purpose	To describe a patient with a LHON phenotype associated with POLG variants.
Methods	Comprehensive ophthalmic examination, retinal imaging, visual field and colour vision testing, brain MRI, biochemical and genetic investigations were performed.
Results	A 25-year-old woman presented with subacute bilateral visual loss progressing over four months to counting fingers in both eyes. Visual fields showed bilateral central scotomata. Colour vision was absent. OCT demonstrated progressive thinning of the ganglion cell layer and temporal retinal nerve fibre layer, consistent with optic atrophy. Fundus examination revealed bilateral temporal optic disc pallor. Brain MRI showed no abnormalities explaining the visual loss, although nonspecific white matter changes greater than expected for age were present. Four months later, progressive sensorineural hearing loss developed. Mitochondrial DNA sequencing, biotinidase activity, anti-MOG, anti-AQP4 and paraneoplastic antibody testing were negative. Whole-exome sequencing identified two POLG variants: c.752C>T, p.(Thr251Ile) and c.1760C>T, p.(Pro587Leu).
Conclusion	POLG-related disease may present as a classic LHON phenotype. Nuclear mitochondrial genes, including POLG, should therefore be considered in patients with suspected LHON, particularly when extraocular features such as hearing loss are present.
Conflict of interest	No

Authors 1

Last name	BERGHMANS
Initials	L
Department	Department of Ophthalmology, Ghent University Hospital
City	Ghent

Authors 2

Last name	DE BAERE
Initials	E
Department	Department of Medical Genetics, Ghent University Hospital
City	Ghent

Authors 3

Last name	POPPE
Initials	B
Department	Department of Medical Genetics, Ghent University Hospital
City	Ghent

Authors 4

Last name	HEMELSOET
Initials	D
Department	Department of Neurology, Ghent University Hospital
City	Ghent

Authors 5

Last name	VAN DE SOMPELE
Initials	S
Department	Department of Medical Genetics, Ghent University Hospital
City	Ghent

Authors 6

Last name	DE ZAEYTIJD
Initials	J
Department	Department of Ophthalmology, Ghent University Hospital
City	Ghent