An international team of researchers said Thursday they have created a map of gene mutations that contribute to the neurodegenerative disorder known as hereditary spastic paraplegia (HSP), which is considered as the first step toward the development of new treatments for the disease.

HSP is characterized by progressive stiffness and contraction of the lower limbs and is associated with epilepsy, cognitive impairment, blindness and other neurological features.

The researchers sequenced the exomes, vital parts of the genome, of more than 120 patients from 55 different families displaying autosomal recessive HSP, which means some siblings were afflicted and some were not.

The researchers identified 13 mutated genes as well as another 18 candidate mutations, most of which were shared by more than half of the family members in the study.

"After uncovering so many novel genetic bases of HSP, we were in the unique position to investigate how these causes link together. We were able to generate an 'HSPome,' a map that included all of the new and previously described causes," senior author Joseph Gleeson, professor of the University of California, San Diego, said in a statement.

The HSPome will help locate and validate even more genetic mutations in patients, and indicate key biological pathways underlying HSP, said the researchers, who were also interested in understanding how HSP relates to other groups of disorders.

They found that the HSPome links HSP to other more common neurodegenerative disorders, such as Alzheimer's disease and amyotrophic lateral sclerosis.

"Knowing the biological processes underlying neurodegenerative disorders is seminal to driving future scientific studies that aim to uncover the exact mechanisms implicated in common neurodegenerative diseases, and to indicate the path toward development of effective treatments," added Gleeson.

The findings were published in the US journal Science.