IgG4 Autoimmune diseases
A brief introduction into IgG4-AID
MuSK Myasthenia Gravis
Imagine your brain sends a clear command for your arm to lift or your mouth to speak, but the message gets lost along the way. For patients living with MuSK Myasthenia Gravis (MuSK-MG), this is not a hypothetical scenario, but a daily reality.
MuSK-MG is a rare, chronic autoimmune disease that most often affects young adults, especially women in their 20s to 40s, although men and older people can also develop it. In our muscle cells, there is a molecule called MuSK (Muscle-Specific Kinase), which acts like an antenna, helping the muscles to receive the "move" signal sent by our nerves. In MuSK-MG patients, the body's defense system mistakenly produces proteins called IgG4 antibodies, which attack these MuSK molecules. Because the signal gets lost, muscles become weak and tired very easily.
What makes MuSK-MG particularly challenging is its fluctuating nature. A person might wake up feeling relatively strong, but by lunchtime, simple actions require massive effort. The symptoms primarily attack the face, neck and shoulders. Patients often struggle with droopy eyelids or double vision, and weak muscles can make it difficult to chew, swallow or talk. Everyday tasks we take for granted, like holding our heads up to look at a screen or lifting our arms to brush our hair, become an exhausting marathon. In severe cases, breathing muscles can be affected, leading to a "crisis" that requires immediate emergency medical care.
Because the weakness comes and goes, diagnosing MuSK-MG requires a careful medical investigation. Doctors rely on clinical observations alongside specialized diagnostic tools. These include neurophysiological testing (to evaluate muscle responses by sending tiny electrical impulses to the nerves), the ice pack test (where an ice pack is held over a drooping eyelid to check for improvement) and blood tests (to detect the specific antibodies attacking the MuSK molecule).
Living with this condition means becoming a master of pacing oneself. Because exhaustion builds with activity and improves with rest, daily life is structured around "good hours". Fortunately, medical treatments play an very important role in expanding these windows of strength. While there is currently no permanent cure, doctors successfully manage the condition using a combination of symptom-relieving medications and immunomodulatory therapies. These include corticosteroids, immunosuppressants like azathioprine, IVIG, plasma exchange (to clean the blood of harmful antibodies), acetylcholinesterase inhibitors, and targeted biological therapies like rituximab. With the right treatment plan, many individuals regain significant physical strength and reclaim their independence.
Why does raising awareness for this rare condition matter so much? On a personal level, knowing the symptoms helps people recognize the warning signs early and seek medical help quickly, avoiding dangerous complications. On a broader level, even though it is a rare disease, the number of diagnosed cases has been rising in recent years. By funding research and understanding how to fix this specific broken signal, scientists can unlock vital secrets about the human immune system. Ultimately, what we learn from MuSK-MG today could pave the way for breakthrough treatments for a wide range of other autoimmune diseases tomorrow.
Autoimmune encephalitis
Albert had always been a happy, intelligent, and very active person. He loved riding bicycles, swimming, and hiking. Even as he grew older and became a grandfather to several children, he stayed energetic and adventurous, always teaching his grandchildren new hobbies and spending time outdoors.
But after Albert turned 72 years old, things slowly began to change. He started having mild memory problems and trouble sleeping. Sometimes he forgot small things or seemed confused. He went to several doctors, but at first nobody could find the cause. After some time, his family noticed that his face and one of his arms would suddenly make quick, strange movements that he could not control. The movements were very brief lasting only a second or two, but they started happening many times throughout the day. Also, he had a seizure, the memory problems started getting worse and he had trouble walking.
Later, doctors diagnosed Albert with a rare disease called LGI1 autoimmune encephalitis. For his diagnosis, doctors did a brain scan and a few other simple tests. They checked if the brain looked inflamed or damaged, how well it was working, and if there were harmful antibodies in his blood. These antibodies attach to a protein named LGI1 that is essential for normal communication in the brain and in the nervous system. By interfering with it, they disrupt how signals are sent, affecting movement control and causing other symptoms Albert is experiencing.
The doctor explained that one approach was to use medication such as corticosteroids and immunosuppressants to calm down the immune system. Plasma exchange could be used to filter his blood to remove the harmful antibodies. The doctor also mentioned IVIG, where healthy antibodies from donated blood were given to help block the harmful ones. In some cases, doctors can also use treatments such as rituximab to kill the cells that produce these antibodies. Together, Albert and his doctor chose the treatment plan and started it. Over time, Albert responded well and began to feel much better.
However, the doctor explained that this illness can be unpredictable. Even after improvement, it can sometimes come back again, so careful follow-up and monitoring are still important.
Autoimmune nodopathies and paranodopathies
Autoimmune nodopathies and paranodopathies are rare diseases of the nerves. They happen when the body's immune system mistakenly attacks important parts of the nerves called the node and paranode. These areas act a bit like "electrical relay stations," where the electrical signals moving through nerves to muscles can "jump over" the gaps in the sheath covering the nerves like an insulation layer. When they are damaged, nerve signals slow down or become blocked, which can lead to weakness and loss of sensation.
These diseases can affect adults of different ages. In some people, the immune system produces antibodies, which are proteins that normally help fight infections, but here attack the body's own nerves instead. Researchers are still learning why this happens, but infections, immune system changes, and genetic factors may all play a role.
Diagnosing autoimmune nodo/paranodopathies can sometimes take time because their symptoms can look similar to other nerve diseases. Doctors usually combine several tests to make the diagnosis. These may include a neurological examination, nerve conduction studies to measure how well nerves send signals, blood tests to look for antibodies, and sometimes spinal fluid analysis or nerve imaging.
Many people first notice weakness in their arms or legs, numbness, tingling, poor balance, or difficulty walking. Some may also experience tremors or problems with fine hand movements such as buttoning clothes or writing. In more severe cases, swallowing or breathing muscles can also be affected.
These diseases matter because early diagnosis and the right treatment can make a big difference. Some patients respond well to treatments that calm down the immune system. However, treatments commonly used for other nerve diseases may not work as well in nodo/paranodopathies, which makes correct diagnosis especially important.
Living with the disease can affect daily life in many ways. Everyday activities such as climbing stairs, carrying groceries, cooking, or working may become more difficult. Fatigue and uncertainty about symptoms can also affect emotional well-being. Support from healthcare professionals, physiotherapists, family members, and patient groups can help people maintain their independence and quality of life.
Research on autoimmune nodopathies and paranodopathies is growing rapidly, and scientists and doctors are working together to better understand these diseases. We hope that our ongoing research will lead to earlier diagnosis, more effective treatments, and improved care, helping affected people maintain their independence and quality of life.
Caspr2 autoimmune encephalitis
Have you ever thought on how the Eurostar crosses the Channel Tunnel in high speed and without any incident every day? This tunnel system requires organized control points that tell trains where they are and regulate speed, distribute electricity along the route, with the aim to maintain a safe and efficient operation. Something very similar happens in our nervous system: neurons are the cellular units that form the fibers that transmit information from our brain to our muscles and organs for them to function properly, see them as the tracks of the train and the information to be the train itself. In the nervous system, these tracks go through high-speed insulated tunnels called "myelin sheaths" allowing signals to travel fast. As in the Eurostar tunnel, in the nervous system there are specialized proteins such as Caspr2 that help organize the signaling checkpoints and infrastructure that keep everything running smoothly and the traffic coordinated.
In Caspr2 autoimmune encephalitis, the immune system (aka the body's own maintenance team) produces IgG4 antibodies targeting the CASPR2 protein, which instead of destroying cells directly, they interfere on how the nerve signaling is organized, like workers incorrectly placing covers over the control panels. It's not that the tracks disappear, but that the traffic-control system along the tracks gets attacked, making the communication between different parts of the train line chaotic and the nervous system unreliable. In patients, this disruption can lead to problems such as seizures, confusion, memory issues, abnormal movements, nerve hyperexcitability, or sleep disturbances, which affect many ordinary daily activities. The disease presents rapidly and unexpectedly, causing a wide range of debilitating symptoms in patients, which leads to significant suffering. The greatest challenge is diagnosing and treating the disease in time to prevent possible long-term complications.
For diagnosing this conditions, doctors currently combine symptoms, brain scans, electrical tests, and more important, they try to identify Caspr2 antibodies in blood or spinal fluid. Like engineers investigating a rail network problem, they look for evidence of what is causing the disruption.
The earlier doctors identify the immune attack, the better the chance of restoring the nervous system's communication, thus preventing larger disruptions across the network.
However, we still do not fully understand why the immune system damages part of the nervous system and how this comes to happen, and that is what we are trying to investigate. The more we understand how diseases like CASPR2 autoimmune encephalitis work, the better we can diagnose them, treat them, and help patients recover.
Anti-IgLON5 disease
Anti-IgLON5 disease is a rare neurological disorder in which the body's immune system attacks its own brain cells (neurons). To understand it, you can think of the brain as a communication network, where neurons constantly send signals to each other. These signals partly depend on a molecule called IgLON5, which helps support normal communication between brain cells. In this disease, the immune system mistakenly produces antibodies against IgLON5 instead of only against harmful invaders like viruses and bacteria.
This abnormal immune response is thought to affect how brain cells function and communicate, leading to a wide range of symptoms. Because it affects only about 1 in every 150,000 people, mostly adults around the age of 69, it is often difficult to diagnose. Diagnosis is usually based on a combination of clinical symptoms, neurological examination, sleep studies, and most importantly the detection of IgLON5 antibodies in patients' samples.
The most common symptoms are sleep disturbances, such as abnormal movements during sleep, breathing difficulties, insomnia, and excessive daytime sleepiness. However, these symptoms can be subtle and may go unnoticed for some time. Therefore, many patients first seek medical attention because of gait problems, such as difficulty walking and imbalance. Difficulty swallowing is also common, and additional neurological symptoms may occur as well.
This disease is critical because it causes progressive dysfunction of neurons, which over time can lead to significant reduction in independence and quality of life because of worsening balance, mobility, and safe swallowing. Without early diagnosis and appropriate immunotherapy, the disease may continue to progress and lead to severe complications such as aspiration and respiratory failure, which can be life-threatening.