Scientists at Ben-Gurion University of the Negev, Israel, studied ten patients from four families that have PCCA2 (Progressive Cerebello-Cerebral Atrophy Type 2).
Children who have the disease appear normal at birth and develop as expected until about six months. However, by one year, patients develop brain atrophy (a loss of brain cells), mental retardation and epilepsy. At three years old, most patients will be in a near-vegetative state.
The work to find the gene behind the condition was led by Professor Ohad Birk and Miora Feinstein, a doctoral student. They found that the disease is caused by two different mutations in the same gene - VPS53.
The exact reasons why VPS53 mutations cause PCCA2 are unclear. However, the researchers that the tiny pockets that carry material around cells, called endosomes, do not move around like they should. As a result, waste material, which should be broken down and destroyed, builds up within the cell.
Professor Birk's group has now discovered more than 20 genetic diseases found in people of Arab and Sephardi Jewish backgrounds. In 2010, they identified mutations in a gene called SESPSECS, which prevent the mineral selenium from being used in the body and cause a very similar disease called PCCA.
'There was an idea that Ashkenazi Jews have more disease than others, but when one begins looking at Sephardic Jewish diseases, they are there', Professor Birk said.
'They have just not been sorted out. Because they have not been sorted out, there was no carrier testing, no prevention programmes or anything. I have shifted part of my lab into this, into Jewish non-Ashkenazi - or Sephardic Jewish - diseases'.
PCCA2 is a recessive disease, meaning that both parents must be carriers of a VPS53 mutation. Children have a 25 percent risk of inheriting two mutated copies of VPS53, and having the disease.
As one in 37 Moroccan Jews carry VPS53 mutations, PCCA2 is now the most common severe genetic disease in this community.
Fifteen percent of Israel's population (one million people) is of Moroccan ancestry. Nearly 100,000 Moroccan Jews also live in the USA, meaning a large number of people are at risk of inheriting the disease.
Carrier testing for SESPSECS mutations was introduced in 2011 for all Jews of Moroccan or Iraqi ancestry. Now researchers have called for routine carrier screening for VSP53 mutations as well. This might even start within the year, and could help reduce the number of people inheriting the disease.
The study was published in the the Journal of Medical Genetics.