Professionals

Ribose-5-phosphate isomerase (RPIA) deficiency is an extremely rare autosomal recessive inborn error of metabolism affecting the non-oxidative branch of the pentose phosphate pathway (PPP).

Fewer than five patients have been reported worldwide, making this one of the rarest known human metabolic disorders.

RPIA encodes ribose-5-phosphate isomerase, which catalyzes the reversible interconversion of ribose-5-phosphate and ribulose-5-phosphate. Deficiency leads to disruption of pentose metabolism and accumulation of polyols, particularly ribitol and D-arabitol, detectable in urine, plasma, CSF, and brain tissue.

Clinically, the disorder presents predominantly as a progressive leukoencephalopathy with neurological deterioration beginning in childhood.