'Families and physicians have been searching for the origins of this rare disorder for years,' said study co-author Dr Chiara Manzini from The George Washington University.
'Children with a similar combination of symptoms had been described in the medical literature before, but it was unclear whether or not it was a new disease. Now we know it's a variant of MD that affects other organs.'
The study, published in the American Journal of Human Genetics, initially examined the DNA of five affected children from four families. A technique called whole-exome sequencing – which specifically looks at the genes which encode proteins – revealed mutations in the INPP5K gene from each affected individual.
The research team went on to block the expression of this gene in zebrafish, which are commonly used model organisms for genetic studies. The affected fish showed similar symptoms to humans who carry the mutation, such as muscle damage and eye defects.
Muscular dystrophy is the term given to a group of progressive diseases that cause muscles to degenerate over time. The disease-causing mutation usually affects the functioning of genes that make proteins required to form and maintain muscles. However, this study revealed mutations in the INPP5K gene affect its function inside the cell, where it is involved with cell signalling and helps to process other proteins. This is why researchers have marked it as a new form of congenital MD.
While the authors note that this finding may not have an immediate impact on the children involved, the study could lead to faster and more precise diagnosis of the disease, and allow families to receive appropriate genetic counselling.
'Early stage research identifying genes for muscle-wasting conditions, such as this, gives us valuable insight into better understanding these complex and rare conditions,' said Robert Meadowcroft, chief executive of Muscular Dystrophy UK.
He added that 'the results from this paper could help some families living with congenital MD to receive a faster diagnosis, paving the way for a potential treatment for this mutation in the future'.
The researchers involved in the study say that more work is needed to understand why the disruption identified in the gene leads to the disorder itself.