Ribose-5-phosphate isomerase deficiency

In the search for an explanation for this rarity, it has been found that the patient has a seldom-seen allelic combination.[2] One allele is a non-functional null allele, while the other encodes for a partially active enzyme. Furthermore, the partially functional allele has expression deficits that depend on the cell type in which it is expressed. Therefore, some of the patient's cells have a considerable amount of Rpi activity, whereas others do not.

The molecular cause of the pathology is not fully understood. One hypothesis is that ribose-5-phosphate may lack for RNA synthesis; another possibility is that the accumulation of D-ribitol and D-arabitol may be toxic.[3]

Symptoms include optic atrophy, nystagmus, cerebellar ataxia, seizures, spasticity, psychomotor retardation, leukoencephalopathy and global developmental delay.[4]

There is no current treatment as well as prognosis for ribose-5-phosphate isomerase deficiency.

In 1999 van der Knaap and colleagues[5][3] described a 14-year-old boy with developmental delay, insidious psychomotor regression, epilepsy, leukoencephalopathy and abnormal polyol metabolism. Later, Naik and colleagues[6] reported a second case, an 18-year-old man with seizures, psychomotor regression and diffuse white matter abnormality. A third case was reported in 2018 by Sklower Brooks and colleagues, a child with neonatal onset leukoencephalopathy and psychomotor delays.[7]