Ribose-5-phosphate isomerase deficiency

Ribose-5-phosphate isomerase deficiency (RPID) is a rare human disorder caused by mutations in ribose-5-phosphate isomerase, an enzyme of the pentose phosphate pathway. With four diagnosed patients over a 27-year period,^{[needs update?]} RPI deficiency is the second rarest disease known as of now,^[when?] with Fields condition being the rarest, affecting two known individuals, Catherine and Kirstie Fields.^[2][3]