Hereditary angioedema with C1 esterase inhibitor deficiency is a rare genetic disorder that causes sudden, unpredictable episodes of severe swelling in different parts of the body, including the face, hands, feet, digestive system, and airways—where it can become life-threatening.

Hereditary ataxia represents a complex group of genetic disorders that cause progressive problems with balance, coordination, and movement, affecting thousands of people and their families around the world.

Hereditary haemorrhagic telangiectasia is a genetic disorder that affects blood vessels throughout the body, causing them to form abnormally and bleed easily. While frequent nosebleeds are the most common sign, this condition can also affect the lungs, brain, liver, and other organs, sometimes leading to serious complications.

Hereditary hypophosphataemic rickets is a group of genetic disorders that prevent the kidneys from properly handling phosphate, a mineral essential for building strong bones and teeth. When phosphate levels drop too low, children develop bone abnormalities like bowed legs, while adults experience bone pain and weakness.

Hereditary motor and sensory neuropathy is a group of inherited conditions that progressively damage the nerves connecting your brain and spinal cord to the rest of your body, causing muscle weakness, sensory changes, and foot problems that can affect your daily life.

Hereditary neuropathic amyloidosis is a rare inherited disease where abnormal proteins build up in the body’s nerves and organs, slowly causing damage that can affect sensation, movement, and many bodily functions.

Hereditary nonpolyposis colorectal cancer (HNPCC) is a type of colorectal cancer caused by genetic changes that run in families, increasing the risk of developing cancer before age 50 and affecting multiple generations.

Hereditary optic atrophy is a group of inherited disorders that damage the optic nerve, causing progressive vision loss that typically begins in childhood or adolescence and affects both eyes.

Heritable pulmonary arterial hypertension is a serious inherited condition that causes high blood pressure in the blood vessels of the lungs, potentially leading to heart failure.

Hernia repair is a surgical procedure used to fix a condition where an organ or tissue pushes through a weak spot in the muscle or tissue wall that normally holds it in place.

Herpes simplex virus is a common infection that affects millions of people worldwide. While there is no cure, the infection can be effectively managed with proper treatment and care.

Herpes simplex meningitis is a viral infection that causes swelling in the protective membranes surrounding the brain and spinal cord. While it can cause severe symptoms, most people recover within weeks with proper treatment.

Once herpes simplex virus enters the body, it remains there for life, mostly dormant in nerve cells. Periodically, the virus can “wake up” and travel back to the skin, causing recurring outbreaks of blisters and sores.

Herpes virus infection is a very common viral condition that affects billions of people worldwide. While there is no cure, most people with herpes experience either no symptoms or mild symptoms that can be effectively managed with treatment.

Herpes zoster, commonly known as shingles, is a painful viral infection that causes a distinctive blistering rash on one side of the body. Anyone who has had chickenpox is at risk, as the same virus remains dormant in the body and can reactivate years later, especially as we age.

Hidradenitis suppurativa is a long-term skin condition that causes painful lumps and abscesses in areas where skin rubs together, such as the armpits, groin, and under the breasts. While there is no cure, various treatments and lifestyle changes can help manage symptoms and improve quality of life.

High grade B-cell lymphoma Burkitt-like lymphoma is a rare and extremely fast-growing type of cancer that affects the body’s infection-fighting system, sharing features with both Burkitt lymphoma and other aggressive B-cell cancers while lacking specific genetic markers that define these diseases.

High grade B-cell lymphoma with Burkitt-like features that has returned after treatment presents one of the most challenging situations in cancer care, with survival outcomes that remain difficult to predict despite advances in understanding these aggressive blood cancers.

High-grade B-cell lymphoma is an aggressive type of blood cancer that grows quickly and requires prompt treatment, but modern therapies can put many people into remission.

Hip arthroplasty, commonly known as hip replacement, is one of the most successful surgeries in modern medicine, performed more than 450,000 times each year in the United States to help people overcome severe hip pain and return to everyday activities.

A hip fracture is a break in the upper portion of the thighbone that most commonly affects older adults and requires prompt medical attention. Each year, more than 300,000 people in the United States sustain a hip fracture, with most occurring in adults 65 or older following household or community falls.

HIV is a virus that attacks the body’s immune system, but with today’s medicines, people with HIV can live long, healthy lives and protect their partners from infection.

Hodgkin’s disease, also known as Hodgkin lymphoma, is a type of cancer that affects the lymphatic system, a vital part of the body’s immune system. Despite being a serious condition, it is considered one of the most curable cancers, with treatment often eliminating all signs and symptoms.

When Hodgkin lymphoma returns after treatment, it’s called recurrent or relapsed disease. While this can be concerning, many people can achieve another remission and may even be cured with further treatment.

While Hodgkin lymphoma has a high cure rate with initial treatment, a significant portion of patients face the challenge of disease that either doesn’t respond to treatment or returns after remission, requiring specialized approaches to achieve successful outcomes.

When cells cannot repair certain types of DNA damage properly, cancer may develop. In advanced ovarian cancer, a condition called homologous recombination deficiency affects about half of all patients and plays a crucial role in determining which treatments may work best.

This less common form of breast cancer requires specialized treatment approaches that target both its aggressive growth patterns and the specific proteins that fuel its development.

Hormone receptor positive breast cancer is the most common form of breast cancer, accounting for 70 to 80% of all cases. This type of cancer uses the body’s natural hormones, particularly estrogen and progesterone, to fuel its growth—but understanding this characteristic also opens the door to targeted treatments that can effectively block these hormones and improve outcomes.

Hormone receptor positive HER2 negative breast cancer is the most common type of breast cancer, accounting for about 70% of all cases. This type responds to hormone-blocking treatments because the cancer cells have receptors for estrogen or progesterone, but don’t have high levels of the HER2 protein.

Hormone refractory breast cancer, also called endocrine-resistant breast cancer, occurs when breast cancer cells that were once controlled by hormone therapy develop the ability to grow without responding to these treatments.

Hormone-dependent prostate cancer is a type of prostate cancer that needs male hormones, particularly testosterone, to grow and survive. This characteristic makes it possible to treat the cancer by reducing or blocking these hormones in the body.

Hormone-refractory prostate cancer represents an advanced stage where cancer continues to grow despite treatments that lower testosterone levels, presenting both complex challenges and evolving treatment options for patients and their healthcare teams.

Hot flushes are sudden waves of intense heat that sweep through your body, often leaving you drenched in sweat and flushed. These uncomfortable episodes affect up to 80% of women during menopause and can disrupt daily life for years.

Human epidermal growth factor receptor (HER) negative refers to a classification used primarily in breast cancer when tumor cells do not produce excess amounts of certain growth factor receptors. Understanding this status is crucial for determining the most appropriate treatment approach for patients.

Human herpesvirus 6 encephalitis is a serious brain infection that primarily affects people with weakened immune systems. While most children are infected with the virus early in life without serious problems, the virus can reactivate later and cause dangerous brain inflammation in vulnerable individuals.

Huntington’s disease is an inherited condition that causes brain cells to gradually break down and die, leading to uncontrollable movements, changes in thinking, and emotional challenges. While there is currently no cure, treatment and support can help people manage symptoms and maintain quality of life for many years.

A hydrocele is a fluid-filled swelling that occurs in the scrotum, the pouch of skin that holds the testicles. While the swelling can be alarming, hydroceles are usually painless and often harmless, particularly in newborn babies where they commonly resolve on their own within the first year of life.

Hydrocephalus is a condition where fluid builds up inside the brain, creating harmful pressure that can damage brain tissue and affect how the brain works.

Hyperadrenocorticism is a condition in which the body produces too much of the hormone cortisol over an extended period, leading to a range of physical and emotional symptoms that can significantly impact daily life and overall health.

Hypercholesterolaemia is a common condition where there is too much “bad” cholesterol in your blood. It affects nearly one-third of adults and significantly increases the risk of heart attacks and strokes. The good news is that most people can manage it through lifestyle changes, and effective medications are available when needed.

Hyperchylomicronaemia, also known as familial chylomicronemia syndrome, is a rare genetic disorder that prevents the body from properly breaking down fats in the blood, leading to dangerously high levels of triglycerides that can cause serious complications including life-threatening inflammation of the pancreas.

Hypereosinophilic syndrome is a rare group of blood disorders caused by an excess of white blood cells called eosinophils, which can damage organs throughout the body. Without treatment, this condition can be life-threatening, but with prompt diagnosis and care, more than 80% of people are alive five years after diagnosis.

Hypergammaglobulinaemia benign monoclonal is a condition that involves abnormal protein production in the blood, though it differs from the more commonly discussed polyclonal form and requires careful understanding to distinguish it from related conditions.

Hyperglycaemia, also known as high blood sugar, occurs when the level of glucose in your blood rises above normal levels. This condition most commonly affects people with diabetes, but it can also develop in those without the disease, particularly during illness or hospitalization.

Hyperhidrosis is a condition where your body sweats much more than it needs to stay cool. This excessive sweating can soak through your clothes, disrupt your daily activities, and cause emotional distress, but there are many treatments available to help you manage it.

Hyperinsulinaemic hypoglycaemia is a serious condition where the pancreas produces too much insulin, causing dangerously low blood sugar levels that can lead to permanent brain damage if not treated promptly.

Hyperinsulinism is a rare and serious disorder where the pancreas produces too much insulin, causing dangerously low blood sugar levels that can permanently harm the brain, especially in newborns and infants.

Hyperkalaemia occurs when potassium levels in your blood rise too high, which can be life-threatening. While mild cases may not show symptoms, severe hyperkalaemia can cause dangerous heart problems that require urgent medical attention.

Hyperlipidemia, also known as high cholesterol, is a common condition where there are too many fats in your blood. While it usually has no symptoms, it can lead to serious problems like heart attack and stroke if left untreated. The good news is that with healthy lifestyle changes and sometimes medication, you can manage your cholesterol levels and protect your heart.

Hyperoxaluria occurs when there is too much oxalate in the urine, leading to kidney stones and potentially serious kidney damage that can affect long-term health.

Primary hyperparathyroidism is a disorder where one or more of the four tiny parathyroid glands in your neck becomes overactive and produces too much parathyroid hormone, leading to high calcium levels in your blood that can affect your bones, kidneys, and other organs.

Secondary hyperparathyroidism is a condition where the parathyroid glands produce too much parathyroid hormone in response to an underlying health problem, most commonly chronic kidney disease or vitamin D deficiency.

Hyperphagia is an intense, persistent sensation of hunger that does not go away even after eating. This condition involves an extreme drive to consume food, food-related behavior problems, and a lack of normal satiety—the feeling of fullness that typically follows a meal.

Congenital adrenal hyperplasia is a group of inherited conditions that affect the adrenal glands and their ability to produce vital hormones, requiring lifelong management to maintain health and prevent serious complications.

Hypersensitivity is an abnormal immune response where the body overreacts to substances that are usually harmless, affecting about 15% of the population and causing conditions ranging from mild allergies to life-threatening reactions.

Hypersomnia makes staying awake during the day extremely difficult, even after a full night’s sleep. This neurological condition can affect every part of your life, from work and school to relationships and safety, but understanding the condition and finding the right treatment can help you manage its impact.

High blood pressure affects nearly half of all adults in the United States and about 1.4 billion people worldwide, yet many don’t even know they have it because it usually causes no symptoms. This silent condition can lead to serious health problems like heart attack, stroke, and kidney disease, but the good news is that lifestyle changes and proper treatment can help keep it under control.

Hyperthyroidism occurs when the thyroid gland makes too much thyroid hormone, causing the body’s metabolism to speed up. This can lead to a wide range of symptoms affecting the heart, weight, energy levels, and emotions. The condition is treatable with medications, radioactive iodine, or surgery.

Hypertonic bladder, commonly known as overactive bladder, is a chronic condition that causes sudden and strong urges to urinate that may be difficult to control, affecting millions of people worldwide and significantly impacting daily activities and quality of life.

Hypertriglyceridaemia is a condition where you have too much of a type of fat called triglycerides in your blood. This condition affects about 1 in 5 adults and can raise your risk of heart disease and, at very high levels, inflammation of the pancreas.