SLC19A3 encodes thiamine transporter 2 (hTHTR2), a plasma membrane protein that mediates high-affinity thiamine (vitamin B1) uptake via a proton antiport mechanism 1. The transporter also mediates H+-dependent pyridoxine (vitamin B6) transport but lacks folate transport activity 1. SLC19A3 contains 12 transmembrane domains and is widely expressed, with highest levels in placenta, kidney, and liver 2. The protein exhibits adipose tissue-specific expression patterns and is regulated during obesity and weight loss 3. Pathogenic variants in SLC19A3 cause thiamine metabolism dysfunction syndrome type 2, also known as biotin-thiamine-responsive basal ganglia disease (BTBGD), characterized by heterogeneous neurological presentations including classical childhood basal ganglia disease, early-infantile Leigh-like syndrome, and adult Wernicke's-like encephalopathy 4. These disorders are triggered by stressors such as fever or trauma and affect basal ganglia, cerebral cortex, thalamus, and periaqueductal regions 4. Treatment consists of lifelong thiamine supplementation alone or combined with biotin, with excellent survival outcomes (100% 3-year survival) when properly treated 5. SLC19A3 is also a target for drug interactions, with medications like fedratinib, amprolium, and hydroxychloroquine inhibiting transporter function 1.