Bilateral optic atrophy as a sequela of delayed biotinidase deficiency diagnosis: a case report

Biotinidase deficiency (BD) is a rare autosomal recessive metabolic disorder that can lead to severe neurological and ophthalmological complications if left untreated. Optic atrophy is a known but often under-recognized sequela of BD, particularly in cases with delayed diagnosis and treatment. We report the case of a 21-year-old female with a history of consanguineous parentage who presented with bilateral vision loss that was more pronounced in the left eye. Her medical history revealed frequent hospitalizations in infancy due to refractory seizures, pulmonary infections, and dermatological manifestations. At the age of one, BD was diagnosed based on undetectable serum biotinidase enzyme activity (0 U/L), and biotin therapy (20 mg/day) was initiated. Despite treatment, ophthalmologic evaluation at age 21 revealed bilateral optic atrophy, decreased visual acuity (OD: 20/200, OS: counting fingers at 1 meter), and visual field defects. Visual evoked potential (VEP) testing showed a reduced amplitude in the left eye, while electroretinography (ERG) remained normal. The patient was advised to continue biotin therapy and to undergo regular ophthalmologic monitoring. This case emphasizes the importance of early diagnosis and intervention in BD to prevent permanent complications, such as optic atrophy and vision impairment. We advocate universal newborn screening for BD and increased awareness among clinicians regarding its ophthalmological manifestations.