Thiamine-responsive megaloblastic anemia (TRMA) is an autosomal recessive disease in which the active thiamine uptake into cells is disturbed. The molecular basis underlying the disorder has been related to mutations in the gene SLC19A2 on chromosome 1q23.3 that encodes a functional thiamine transporter. The protein is predicted to have 12 transmembrane domains. TRMA is characterized by sensorineural deafness, diabetes mellitus, megaloblastic anemia, and cardiomyopathy. Optic nerve atrophy and retinal dystrophy have been reported in a small number of patients. We report a 15-year-old girl with TRMA and cone-rod dystrophy and confirm that retinal dystrophy may form part of the syndrome. Differential diagnosis of syndromes with deafness, diabetes mellitus, and optic nerve atrophy or retinal dystrophy are discussed. The authors suggest that ERG be performed in all patients with TRMA.