Abstract
Biotin-thiamine-responsive basal ganglia disease (BTBGD) is a treatable neurometabolic disease caused by variants in SLC19A3. Typical imaging features include symmetrical involvement of the caudate nuclei and putamina.
The study sought to explore classical BTBGD without caudate nucleus involvement, to highlight the importance of recognizing this new pattern early in the disease.
Individuals with genetically confirmed BTBGD who harbored the same homozygous variant: NM_025243.4 (SLC19A3): c.1264A > G (p.Thr422Ala) and had atypical neuroimaging were recruited.
Nine patients with BTBGD had atypical neuroimaging findings on the first MRI scan. The median age at symptom onset was 3 years. All patients presented with classical clinical features of subacute encephalopathy, dystonia, ataxia, and seizures. During the acute crisis, MRI revealed bilateral and symmetric involvement of the putamina in all patients; one showed small caudate nuclei involvement. In addition, the thalami, cerebellum, and brain stem were involved in six patients, seven patients, and three patients, respectively. Treatment included a combination of high doses of thiamine and biotin. One patient died; he did not receive any vitamin supplementation. Two patients who were treated late had severe neurological sequelae, including generalized dystonia and quadriplegia. Six patients treated early had good outcomes with minimal sequelae, including mild dystonia and dysarthria. Two patients showed the classical chronic atrophic and necrotic changes already described.
The early atypical neuroimaging pattern of BTBGD described here, particularly the lack of caudate nucleus involvement, should not dissuade the clinician and radiologist from considering a diagnosis of BTBGD.