World’s Rarest Disease – Ribose-5-Phosphate Isomerase Deficiency

Human body works owing to several chemical reactions which take place continuously. These life-perpetuating reactions are technically called metabolism. Naturally found chemicals called enzymes play an important role in deciding the pace of these reactions. They activate and deactivate signaling molecules which either start these reactions or bring them to a halt.

When there is a deficiency in the production of these vital chemicals, the entire body suffers from an ailment. There are several types of diseases caused because of the less production of enzymes. One such disease belonging to this class is the Ribose-5-phosphate isomerase deficiency (RPI deficiency). Only one case of this ailment has been recorded in history, making it the rarest ailment in the world.

R5P-Ru5P Conversion

Basics to Know: The food we eat is broken down into glucose. The enzyme in question whose deficiency causes RPI disorder is the Ribose-5-phosphate isomerase. It helps in the conversion of a chemical ribose-5-phosphate (R5P) into another chemical ribulose-5-phosphate (Ru5P).This conversion helps the body to in turn convert glucose into adenosine triphosphate (ATP). The latter is a form of energy which is readily used by the cells to carry out their functions effectively.

Moreover, the conversion reaction also helps in the protection of the body from an unavoidable and harmful chemical process called oxidative stress. This reaction takes place primarily during the process of respiration and involves production of certain highly reactive chemicals called free radicals. Excess presence of these free radicals can damage the building blocks of life -the cells.

What is the Ribose-5-Phosphate Isomerase Deficiency (RPI Deficiency)?
All cells carry out their functions by following the chemical instructions present inside their nucleus. These instructions are called genes made up of a group of chemical structures known as chromosomes. Chemical molecules called DNAs form these chromosomes. Other genetic molecules, called RNAs, read the instructions made up of the DNAs and produce chemicals called proteins which carry out the tasks of the cells. Enzymes like the Ribose-5-phosphate isomerase are also such proteins.

Certain environmental factors at times change the positions of the DNA molecules in the chromosomes. Such an event is technically called mutation. When mutation occurs in the RPI gene from which Ribose-5-phosphate isomerase enzyme is produced, RPI deficiency is caused.

The exact mechanism of how less production of this vital enzyme occurs because of mutation is not understood yet. There is only one patient diagnosed of this disease in medical history. This patient was a boy and the diagnosis was made in 1984 through magnetic resonance imaging technique.

As a consequence of the RPI disorder, the boy developed a brain disease called leukoencelopathy. The term is used to describe a group of ailments where the white matter in the brain gets affected.

Conclusion:The diagnosed case of Ribose-5-Phosphate Isomerase deficiency in 1984 was reported in 1999. It took 15 years for the experts to establish a relation between the cause (less production of the enzyme Ribose-5-phosphate isomerase) and the effect (Ribose-5-Phosphate Isomerase Deficiency). No new case of this disease has been reported thereafter.

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