title: A treatable cause of myelopathy and vision loss mimicking neuromyelitis optica spectrum disorder: late-onset biotinidase deficiency.
abstract: Biotinidase deficiency is characterized by severe neurological manifestations as hypotonia, lethargy, ataxia, hearing loss, seizures and developmental retardation in its classical form. Late-onset biotinidase deficiency presents distinctly from the classical form such as limb weakness and vision problems. A 14-year-old boy presented with progressive vision loss and upper limb weakness. The patient was initiated steroid therapy with a preliminary diagnosis of neuromyelitis optica spectrum disorder due to the craniospinal imaging findings demonstrating optic nerve, brainstem and longitudinally extensive spinal cord involvement. Although the patient exhibited partial clinical improvement after pulse steroid therapy, craniocervical imaging performed one month after the initiation of steroid therapy did not show any regression. The CSF IgG index was <0.8 (normal: <0.8), oligoclonal band and aquaporin-4 antibodies were negative. Metabolic investigations revealed a low biotinidase enzyme activity 8% (0.58 nmoL/min/mL; normal range: 4.4 to 12). Genetic testing showed c.98-104delinsTCC and p.V457 M mutations in biotinidase (BTD) gene. At the third month of biotin replacement therapy, control craniospinal MRI demonstrated a complete regression of the lesions. The muscle strength of the case returned to normal. His visual acuity was 7/10 in the left eye and 9/10 in the right. The late-onset form of the biotinidase deficiency should be kept in mind in all patients with myelopathy with or without vision loss, particularly in those with inadequate response to steroid therapy. The family screening is important to identify asymptomatic individuals and timely treatment.
authors.affiliation: Department of Pediatrics, Division of Child Neurology, Ege University Medical Faculty, 35100-Bornova, Izmir, Turkey. sanemeyll@gmail.com.
authors.forename: Sanem
authors.initials: S
authors.lastname: Yilmaz
authors.affiliation: Department of Pediatrics, Division of Child Neurology, Ege University Medical Faculty, 35100-Bornova, Izmir, Turkey.
authors.forename: Mine
authors.initials: M
authors.lastname: Serin
authors.affiliation: Department of Pediatrics, Division of Metabolism and Nutrition, Ege University Medical Faculty, Izmir, Turkey.
authors.forename: Ebru
authors.initials: E
authors.lastname: Canda
authors.affiliation: Department of Radiology, Division of Neuroradiology, Ege University Medical Faculty, Izmir, Turkey.
authors.forename: Cenk
authors.initials: C
authors.lastname: Eraslan
authors.affiliation: Department of Pediatrics, Division of Child Neurology, Ege University Medical Faculty, 35100-Bornova, Izmir, Turkey.
authors.forename: Hande
authors.initials: H
authors.lastname: Tekin
authors.affiliation: Department of Pediatrics, Division of Metabolism and Nutrition, Ege University Medical Faculty, Izmir, Turkey.
authors.forename: Sema Kalkan
authors.initials: SK
authors.lastname: Ucar
authors.affiliation: Department of Pediatrics, Division of Child Neurology, Ege University Medical Faculty, 35100-Bornova, Izmir, Turkey.
authors.forename: Sarenur
authors.initials: S
authors.lastname: Gokben
authors.affiliation: Department of Pediatrics, Division of Child Neurology, Ege University Medical Faculty, 35100-Bornova, Izmir, Turkey.
authors.forename: Hasan
authors.initials: H
authors.lastname: Tekgul
authors.affiliation: Department of Pediatrics, Division of Child Neurology, Ege University Medical Faculty, 35100-Bornova, Izmir, Turkey.
authors.forename: Gul
authors.initials: G
authors.lastname: Serdaroglu
mesh_terms: D000293:Adolescent; D001710:Biotin / Q000627:therapeutic use*; D028921:Biotinidase Deficiency / Q000150:complications / Q000000981:diagnostic imaging* / Q000188:drug therapy; D003937:Diagnosis, Differential; D006801:Humans; D008297:Male; D009471:Neuromyelitis Optica / Q000150:complications / Q000000981:diagnostic imaging* / Q000188:drug therapy; D013118:Spinal Cord Diseases / Q000150:complications / Q000000981:diagnostic imaging* / Q000188:drug therapy; D016896:Treatment Outcome; D014786:Vision Disorders / Q000150:complications / Q000000981:diagnostic imaging* / Q000188:drug therapy
chemical_list: D001710:Biotin
keywords: Late-onset biotinidase deficiency; Myelopathy; Neuromyelitis optica spectrum disorder; Vision loss