Gene link found for paralyzing nerve disease ALS

ATLANTA, Georgia (Reuters) -- Researchers said on Tuesday they were homing in on a new gene associated with the paralyzing disease known as Lou Gehrig's disease, ALS or motor neuron disease, which may shed light on what causes the illness and may offer treatments for it.

The new gene also seems to be linked with a rare form of dementia that affects these patients, the researchers report in this week's Journal of the American Medical Association.

Amyotrophic lateral sclerosis or ALS causes a progressive degeneration of the nerves and has no cure. Patients become gradually paralyzed and die. Baseball player Lou Gehrig died of ALS and physicist Stephen Hawking is confined to a wheelchair because of it.

The patients involved in the study all seemed to have inherited ALS, because it ran in their families, Betsy Hosler of Massachusetts General Hospital and Harvard University, who worked on the study, told a briefing of science reporters.

"What we have done ... is to study families," Hosler said. Most cases of ALS are sporadic -- they occur with no pattern. But in 10 percent of cases it runs in families.

"Occasionally if you ask (a patient) will say 'oh yes, my uncle had the same disease, or a cousin'," Hosler said. In such cases, doctors believe an inherited genetic defect must be responsible.

Usually, an ALS patient endures the inexorable paralysis with a clear mind. But in about 5 percent of both sporadic and familial ALS, the patient develops dementia.

Hosler's team looked at 500 people from 20 families that had members with both ALS and dementia.

About 25 percent of familial cases are linked to a defect in a gene known as SOD1. This leaves 75 percent of cases unexplained.

Looking for a gene is like trying to put a puzzle together without knowing what the final picture will be, Hosler said. But her team seems to have found a common genetic pattern on chromosome 9, she said.

"We hope that this locus (area on the chromosome where the gene is found) will now account for another fairly large group of the ALS cases," she said.

It may also shed some light on the causes of dementia.

"One of the major questions in studying ALS has always been why just the motor neurons?" Hosler said. The disease affects only nerve cells that are associated with moving muscles.

"Now we have a handle perhaps in these patients on the cause of death of several classes of neurons. In these patients, not only motor neurons but neurons in frontal temporal lobes (of the brain) are affected."

Their patients, when they develop dementia, have inappropriate, impulsive behavior, have trouble performing daily tasks and suffer memory changes.

Hosler said it is far too soon to know what treatments or even cures might be offered by the study. But the area they have identified is near other genes associated with damage to nerve and muscle function.

Nearby is a gene associated with a disease known as Friedrick's ataxia, marked by an inability to carry out tasks such as buttoning a shirt; and one associated with a similar illness known as choreoacanthocytosis, which may or may not be related to ALS, Hosler said.

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Lou Gehrig's Disease - Doctor's Guide to the Internet
MedicineNet.com - Amyotrophic Lateral Sclerosis

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