Huntington’s Disease Protects Against Cancer
People with motor neuron diseases such as Huntington’s disease seem to be protected against cancer, researchers reported.
The underlying cause of the “PolyQ” diseases is an increased number of glutamine units in different genes, according to Jianguang Ji, MD, and colleagues at Lund University in Malmö, Sweden.
But patients with the polyglutamine tracts – and therefore one of nine different PolyQ diseases - have significantly lower cancer risks than the general population, Ji and colleagues reported online in The Lancet Oncology.
The finding suggests that a common mechanism - perhaps related to the increased number of glutamine units - underlies the protective effect, they argued.
The PolyQ diseases include Huntington’s, spinobulbar muscular atrophy (SBMA), dentatorubral and pallidoluysian atrophy, and six types of spinocerebellar ataxia.
They are all characterized by progressive degeneration of motor neurons, although the details vary. All have an increased number of repeated genetic sequences - cystosine-adenine-guanine - but in different genes.
What is Huntington’s disease?
Huntington’s disease (HD) is named after George Huntington who first described it in 1872. It is an inherited, genetic condition that affects the brain and nervous system. It can interfere with movements of your body, can affect your cognition (your perception, reasoning, awareness, thinking and judgement) and can lead to a change in your behaviour.
Observations have suggested that Huntington’s patients have a lower risk of cancer, the researchers noted, but those could be accounted for by a range of factors, including a tendency for doctors to miss the cancer diagnosis because of concern for the main disease.
To help clarify the matter, Ji and colleagues turned to Sweden’s nationwide medical records system, which allowed them to find patients with Huntington’s, spinobulbar muscular atrophy, and hereditary ataxia (which was used as a proxy for spinocerebellar ataxia).
The researchers compared cancer incidence in those patients and their unaffected parents with incidence in the general population of Sweden between January 1969 and December 2008.
All told, they found 1,510 patients with Huntington’s, 471 with SBMA, and 3,425 with hereditary ataxia. They found:
Cancer was diagnosed in 91 Huntington’s patients, or 6%, leading to a standardized incidence ratio of 0.47 (95% CI 0.38 to 0.58) compared with the general population.
34 (or 7.2%) of SBMA patients had a cancer diagnosis, yielding a standardized incidence ratio of 0.65 (95% CI 0.45 to 0.91).
And 421 (or 12.3%) of the hereditary ataxia patients had cancer, leading to standardized incidence ratio of 0·77 (95% CI 0.70 to 0.85).