# Biotinidase Deficiency: Report of a Tunisian Case With Neuromyelitis Optica-Like Presentation and Review of the Literature

## TL;DR

This paper reports a rare case of biotinidase deficiency in Tunisia, where the patient showed symptoms similar to a neurological disorder but improved with biotin treatment.

## Contribution

The first genetically confirmed Tunisian case of biotinidase deficiency with an atypical neuromyelitis optica-like presentation is reported.

## Key findings

- The patient showed cutaneous symptoms initially misdiagnosed as dermatophytosis.
- The patient later developed opticospinal syndrome resembling neuromyelitis optica but improved with biotin.
- A literature review highlights similar pediatric cases with opticospinal syndromes due to biotinidase deficiency.

## Abstract

Biotinidase deficiency is a rare treatable metabolic disorder caused by biallelic mutations in the BTD gene. In the absence of neonatal screening and treatment, affected children develop typically optic atrophy, hypotonia, early onset seizures, developmental delay, and cutaneous manifestations. Some patients may have atypical presentations mimicking a demyelinating disorder of the central nervous system. We report on the first genetically confirmed Tunisian patient with biotinidase deficiency who presented initially with cutaneous manifestations misdiagnosed as dermatophytosis and subsequently with an opticospinal syndrome leading to the diagnosis of seronegative neuromyelitis optica spectrum disorder that was dramatically improved under biotin. We carry on a review of the literature of the previously reported pediatric cases with an opticospinal syndrome revealing biotinidase deficiency.