A newly-discovered mutation within the immune system can, in certain cases, lead to life-threatening complications from chickenpox infections. For one in every 5,000 people that could lead to brain inflammation, and for one of every 500 people it could lead to severe pneumonia. Those complications, while uncommon, could lead to death. Prior to this discovery, the cause of those complications was unknown, leading to an inability to predict who might be susceptible.
Those affected have mutations in RNA polymerase III, also known as POL III. That is the sensor used by the body to recognize the varicella zoster virus that causes chickenpox and shingles. Patients who suffered severe complications from chickenpox had a POL III mutation that caused the body’s immune system to fail to recognize the infection with the chickenpox virus. Therefore the immune system did not put up any defense against the virus and the virus was able to spread within the body, in some cases eventually reaching the brain.
While the sample size of this observation was very small, it may nonetheless provide insights into how to predict chickenpox complications, and may very well also provide insights into combating complications from other common diseases that afflict otherwise healthy individuals.