Acquired haemophilia is a rare but potentially life-threatening bleeding disorder that can appear suddenly in people who have never had bleeding problems before. Unlike the inherited form of haemophilia, this condition develops when the body’s immune system mistakenly attacks its own clotting factors.

Activated PI3 kinase delta syndrome is a rare inherited immune disorder that leaves people vulnerable to repeated infections and other serious health problems. First identified in 2013, this condition affects the immune system’s ability to fight bacteria and viruses, often leading to a complex pattern of symptoms that can vary widely from one person to another.

Acute respiratory distress syndrome (ARDS) is a life-threatening lung injury that causes fluid to build up in the tiny air sacs of your lungs, leading to dangerously low oxygen levels in your blood. This serious condition usually develops within hours to days after a major illness or injury, and requires immediate intensive care treatment.

Adrenocortical carcinoma is a rare but aggressive cancer that develops in the outer layer of the adrenal glands, small organs that sit on top of your kidneys and produce vital hormones. Though it affects only about 1 or 2 people per million each year, this cancer can cause serious health problems by releasing excessive amounts of hormones or growing large enough to press on nearby organs.

Adrenogenital syndrome, also known as congenital adrenal hyperplasia, is a group of genetic disorders that affects the adrenal glands and their ability to produce vital hormones your body needs to function properly.

Advanced systemic mastocytosis is a rare and serious blood disorder where abnormal mast cells build up uncontrollably in various organs, potentially causing organ damage and life-threatening complications.

Aicardi-Goutières syndrome is a rare inherited disease that primarily attacks the brain’s white matter, triggering an immune system response that mistakenly turns against the body itself, leading to serious neurological problems that can appear at birth or develop within the first months of life.

Alagille syndrome is a genetic condition affecting multiple organs, most notably causing malformed or too few bile ducts in the liver, leading to bile buildup that damages liver tissue. This rare disorder can also affect the heart, eyes, bones, kidneys, and blood vessels, with symptoms ranging from mild to life-threatening.

Alexander disease is a rare genetic disorder that progressively damages the nervous system, causing the protective coating around nerve fibers in the brain to deteriorate over time and leading to serious neurological problems.

Alport’s syndrome is a rare genetic condition that affects the kidneys, ears, and eyes. It occurs when the body cannot produce normal proteins needed for healthy kidney function, which can lead to kidney failure over time.

Alternating hemiplegia of childhood is a rare brain disorder that causes sudden, temporary paralysis in young children, along with developmental challenges and other symptoms that can significantly impact their quality of life.

Alveolar rhabdomyosarcoma is a rare and aggressive form of soft tissue cancer that typically strikes teenagers and young adults. This cancer develops from skeletal muscle cells and often appears in the arms, legs, or trunk, spreading rapidly and presenting unique treatment challenges.

Amyotrophic lateral sclerosis is a progressive nervous system disease that affects nerve cells in the brain and spinal cord, leading to loss of muscle control. While there is currently no cure, treatments and supportive care can help manage symptoms and improve quality of life.

Anaplastic thyroid cancer is one of the most aggressive forms of cancer affecting the thyroid gland, growing rapidly and often spreading to other parts of the body before diagnosis, yet recent advances in targeted treatments offer new hope for some patients.

Andersen-Tawil syndrome is a rare genetic disorder that affects the muscles, heart, and physical development, causing episodes of muscle weakness, abnormal heart rhythms, and distinctive physical features in those affected.

Angelman syndrome is a rare genetic disorder that primarily affects the nervous system, causing severe developmental delays, intellectual disability, and problems with movement and speech. Despite these challenges, people with this condition often have a remarkably happy demeanor, with frequent smiling and laughter.

Angiosarcoma is a rare and aggressive cancer that starts in the lining of blood vessels or lymph vessels, most often appearing on the skin of the head and neck but capable of developing almost anywhere in the body.

Metastatic angiosarcoma is an advanced and extremely aggressive form of a rare cancer that originates from blood or lymph vessel cells and has spread to other parts of the body, with survival measured in months rather than years.

Angiosarcoma is a rare and aggressive cancer that begins in the cells lining blood vessels or lymph vessels. When detected before it spreads to other parts of the body, it is called non-metastatic angiosarcoma. Understanding this condition, its symptoms, and treatment options can help patients make informed decisions about their care.

Recurrent angiosarcoma is a highly aggressive cancer that returns after initial treatment, presenting one of the most challenging situations in cancer care. Understanding the nature of recurrence and available treatment options can help patients and their families navigate this difficult diagnosis.

Antisynthetase syndrome is a rare condition where your immune system mistakenly attacks your own body, causing inflammation in muscles, joints, lungs, skin, and blood vessels.

Antithrombin III deficiency is a rare blood disorder that disrupts the body’s natural ability to control blood clotting, putting people at risk for dangerous blood clots that can affect the legs, lungs, and other vital organs.

Arterial tortuosity syndrome is a rare genetic disorder that causes blood vessels to become twisted, elongated, and prone to serious complications that can affect the heart, brain, and other vital organs.

Atypical haemolytic uraemic syndrome is a rare, potentially life-threatening condition where the immune system mistakenly attacks blood vessel cells, forming dangerous clots that can damage kidneys and other vital organs.

Atypical teratoid/rhabdoid tumor (ATRT) is a very rare and aggressive cancer of the brain or spinal cord that grows quickly and requires immediate medical attention.