Ribose 5-phosphate isomerase deficiency is a rare genetic leukoencephalopathy caused by pathogenic sequence variants in RPIA, that encodes ribose 5-phosphate isomerase, an enzyme in the pentose phosphate pathway. Till date, only three individuals with ribose 5-phosphate isomerase deficiency have been described in literature. We report on a subject with RPIA associated progressive leukoencephalopathy with elevated urine arabitol and ribitol levels and a novel missense variant c.770T > C p.(Ile257Thr) in exon 8 of RPIA. We also compare the phenotypes of all the four subjects. Our report confirms the phenotype and the genetic cause of this condition.