Ribose-5-phosphate isomerase deficiency

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Ribose-5-phosphate isomerase deficiency
Other namesRPI deficiency[1]

Ribose-5-phosphate isomerase deficiency is a human disorder caused by mutations in ribose-5-phosphate isomerase, an enzyme of the pentose phosphate pathway. With only three diagnosed patients over a 27-year period, RPI deficiency is the second rarest disease known as of now, being beaten only by Fields Condition.[2]


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.[citation needed]

The molecular cause of the pathology is not fully understood. One hypothesis is that ribose-5-phosphate may be insufficient 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 or 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]


  1. ^ "OMIM Entry - # 608611 - RIBOSE 5-PHOSPHATE ISOMERASE DEFICIENCY". omim.org. Retrieved 16 March 2019.
  2. ^ a b Huck JH, Verhoeven NM, Struys EA, Salomons GS, Jakobs C, van der Knaap MS (April 2004). "Ribose-5-phosphate isomerase deficiency: new inborn error in the pentose phosphate pathway associated with a slowly progressive leukoencephalopathy". American Journal of Human Genetics. 74 (4): 745–51. doi:10.1086/383204. PMC 1181951. PMID 14988808.
  3. ^ "Ribose 5-Phosphate Isomerase Deficiency disease: Malacards - Research Articles, Drugs, Genes, Clinical Trials". www.malacards.org. Retrieved 2018-03-05.
  4. ^ van der Knaap MS, Wevers RA, Struys EA, Verhoeven NM, Pouwels PJ, Engelke UF, Feikema W, Valk J, Jakobs C (December 1999). "Leukoencephalopathy associated with a disturbance in the metabolism of polyols". Annals of Neurology. 46 (6): 925–8. doi:10.1002/1531-8249(199912)46:6<925::aid-ana18>3.0.co;2-j. PMID 10589548.
  5. ^ Naik N, Shah A, Wamelink MC, van der Knaap MS, Hingwala D (September 2017). "Rare case of ribose 5 phosphate isomerase deficiency with slowly progressive leukoencephalopathy". Neurology. 89 (11): 1195–1196. doi:10.1212/WNL.0000000000004361. PMID 28801340.
  6. ^ Brooks SS, Anderson S, Bhise V, Botti C (October 2018). "Further Delineation of Ribose-5-phosphate Isomerase Deficiency: Report of a Third Case". Journal of Child Neurology. 33 (12): 784–787. doi:10.1177/0883073818789316. PMID 30088433.

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