The infection enigma: why some people die from typically harmless germs

[Jaybee00]

Partially Paywalled—seems interesting.

The infection enigma: why some people die from typically harmless germs

Millions of people worldwide carry genetic mutations that weaken their immune system.

www.nature.com

 

[Yann04]

Millions of people worldwide carry genetic mutations that weaken their immune system.

Michael Levin had just started working as a paediatric infectious-disease doctor in London when he received an urgent call from a hospital in Malta. It was the early 1980s, and a young boy had been brought in with symptoms of a severe infection that was spreading through his body, damaging multiple organs and tissues. But his doctors could find no trace of a pathogen.

The boy was flown to Levin’s hospital for further tests. To the surprise of Levin and his colleagues, the culprit was a common bacterium: Mycobacterium fortuitum, which lives in water and soil, and is usually harmless. “Everyone’s exposed to them, but almost no one gets ill,” says Levin, who is now at Imperial College London. Despite aggressive treatment, the boy eventually passed away.

Levin and his colleagues eventually identified what made these children so sick: a genetic mutation affecting a receptor for interferon-γ, an immune molecule with myriad functions, including regulating inflammation. Not long after that, a group in France discovered that similar mutations were responsible for rare cases of severe disease caused by another mycobacterial species — this time, a weakened form used as a tuberculosis vaccine.

Researchers have since amassed a broad library of mutations in hundreds of genes that underlie ‘inborn errors of immunity’ (IEIs) and that make millions of people around the world susceptible to a wide range of infectious diseases and immune-linked ailments that many people can simply shrug off.