What is OTCD? — Chromatography Explores

There are many ways to diagnose medical conditions, especially in children. Some are really straightforward like the sniffles and temperature that comes with a common cold. Others are harder to spot and the first thing you sense is that you feel off-colour, which is soon followed by spots covering your body as chicken pox breaks out. And some are downright difficult to spot like OTCD.

A recent paper published in the International Journal of Clinical and Experimental Medicine — A novel mutation in ornithine transcarbamylase gene identified from a Chinese child with ornithine transcarbamylase deficiency — highlights one method that makes this tricky to diagnose condition a little easier to spot. But what is OTCD and how has chromatography helped find a way to spot the condition in infants?

OTCD — urea cycle disorder

Ornithine transcarbamylase deficiency — OTCD — is an inherited condition that can cause potentially harmful levels of ammonia to build up in the body. OTC is an enzyme involved in the reaction between carbamoyl phosphate and ornithine. It is found in both plants and animals — and in mammals is found in the mitochondria and is involved in the urea cycle.

When we eat, our bodies break down the food to release the nutrients so our bodies can use them. Proteins are one of the major nutrients needed by the body. When proteins are broken down, ammonia is released as a waste product which is processed and removed from the body. One of the enzymes involved in the removal of ammonia is OTC — and if the enzyme is not working correctly then we can suffer from OTCD which leads to high levels of ammonia in the body.

Finding the genes

OTC is a genetic condition with genes located on the X-chromosome — hence it affects males more than females. Babies with OTCD either have faulty genes for OTC or cannot make enough OTC. Therefore, the body cannot remove the ammonia through urine. High ammonia can cause ataxia, lethargy and even death if it is not treated.

Early diagnosis of OTCD can help reduce the mortality and disability linked to the condition. One method is by finding mutations in the gene coding for OTC and this is what the study linked above set out to accomplish — thereby increasing the understanding of OTCD.

The team report that in patients with typical OTCD, serum samples show high levels of the amino acid glutamate and high levels of uracil and orotic acid in the urine of patients are measured using chromatography. Chromatography is commonly used to analyse biological samples as discussed in the article, LC/MS/MS Analysis Using On-line Cartridges for the Removal of Phospholipids from Protein Precipitated Biological Fluid Samples.

The team managed to uncover a novel mutation in the OTC gene. Work that can help to improve early diagnosis and reduce the mortality rate of OTCD.