Riboflavin transporter deficiency (RTD), formerly known as Brown-Vialetto-Van Laere syndrome, is a rare condition that causes progressive neurological syndromes in early life featured by auditory and optic neuropathy, muscle weakness involving bulbar and diaphragm and sensory ataxia (Tyler Allison, 2017).  SLC52A3 and SLC52A2 are the two genetic mutations responsible for the two main RTD types, type 3 and 2. Fatality usually occurs at around 9 years in untreated cases (JK Mah, 2017), but long-term survival into late adulthood has reported to treatment with high dose oral riboflavin (Bregje Jaeger, 2016).   

Case summary: We report two long-term survivors of RTD type 2 due to compound heterozygous 185 T>G and 1258G>A mutations on gene SLC 2A2. They are two brothers of a heavily affected family where two female siblings deceased in childhood from similar clinical syndromes. Brother one, the eldest RTD survivor so far is at age 67 in year 2018 and brother two is at age 54. Both of them have significant visual impairment from optic nerve atrophy, sensory ataxia but no muscle weakness. Their muscle biopsies both showed decreased muscle adenosine monophosphate (AMP) deaminase activity but otherwise morphologically unremarkable. Further genetic testing looking for AMPD1 mutation is in process. Whole genome sequencing confirmed genetic mutations in 2016 for the two brothers; nevertheless, subsequent high dose oral riboflavin did not render clinical benefit.  

Discussion: Co-existing riboflavin transporter deficiency (RTD) type 2 and muscle AMP deaminase deficiency has not been seen in published literature. Apart from a genetically favourable interaction,   AMP deaminase deficiency might have helped in preserving muscle function and therefore survival from accumulations of AMP in muscle (Fabrice Rannou, et. al 2017).