Retroperitoneal fibrosis is a rare condition where scar-like tissue grows behind the abdominal cavity, potentially squeezing vital organs like the ureters, kidneys, and major blood vessels. While most cases have no known cause, early diagnosis and treatment can lead to full recovery for many patients.

Rett syndrome is a rare genetic disorder that disrupts brain development, causing severe physical and mental disabilities primarily in girls. After months of normal growth, children lose abilities they once had—from speaking and walking to using their hands purposefully—creating a profound impact on nearly every aspect of their lives.

Rhabdoid tumour is a rare and highly aggressive cancer that primarily affects babies and very young children, developing rapidly in the kidneys, brain, soft tissues, or other organs throughout the body.

Rhabdoid tumour of the kidney is one of the most aggressive childhood cancers, striking primarily infants and toddlers with devastating speed and intensity.

Rhabdomyosarcoma is a rare type of cancer that develops in muscle tissue and primarily affects children and teenagers, though adults can also be diagnosed. This aggressive disease requires a combination of treatments and can occur anywhere in the body, making early recognition of symptoms crucial for better outcomes.

When rhabdomyosarcoma returns after treatment, it presents one of the most challenging situations in childhood cancer care, with nearly one-third of patients with localized disease and over two-thirds with metastatic disease experiencing recurrence, typically within three years of initial diagnosis.

Rhegmatogenous retinal detachment is a serious eye emergency where a tear in the retina allows fluid to seep underneath, causing it to separate from the back of the eye. Without prompt treatment, this condition can lead to permanent vision loss.

Rheumatic disorders represent a large group of over 200 conditions that primarily affect the joints, muscles, bones, and connective tissues throughout the body, causing pain, swelling, and difficulty with daily activities.

Rheumatoid arthritis is a long-term condition where the immune system attacks the body’s own joints, causing pain, swelling and stiffness that can affect daily activities and quality of life.

Allergic rhinitis, commonly known as hay fever, affects millions of people worldwide, causing sneezing, congestion, and itchy eyes when the immune system overreacts to harmless particles in the air.

Richter’s syndrome is a rare but serious complication where chronic lymphocytic leukemia transforms rapidly into a more aggressive form of cancer, usually an aggressive type of lymphoma, requiring immediate medical attention and specialized treatment.

Right ventricular dysfunction occurs when the right side of your heart cannot pump blood effectively to your lungs. This condition can lead to fluid buildup in your body, causing swelling in your legs and abdomen, and can significantly impact your overall health and quality of life.

ROHHAD syndrome is an extremely rare and life-threatening disorder that causes previously healthy children to suddenly gain dramatic amounts of weight, develop serious breathing problems, and experience multiple body system failures. With fewer than 200 documented cases worldwide, this mysterious condition poses unique challenges for families and doctors alike.

Rosai-Dorfman syndrome is a rare condition where the body produces too many white blood cells called histiocytes, which can accumulate in lymph nodes and other parts of the body, causing swelling and various symptoms depending on where these cells collect.

Round cell liposarcoma is a rare cancer that develops in fat cells, usually appearing as a slow-growing lump in the arms or legs, most commonly affecting people between the ages of 20 and 40.

Rubella is a viral infection that usually causes mild symptoms in most people, but it poses a serious threat to unborn babies when it infects pregnant women, potentially leading to severe birth defects or pregnancy loss.

Salivary gland cancer is a rare disease that forms in the glands that produce saliva in your mouth and throat. Although uncommon, it requires specialized care and attention, as the type and location of the tumor significantly affects treatment and recovery.

SAPHO syndrome is a rare condition that combines bone and joint inflammation with skin problems, creating a unique challenge for both patients and doctors trying to understand and manage this complex disorder.

Sarcoidosis is a condition where the immune system overreacts and forms tiny lumps called granulomas in various organs of the body, most commonly in the lungs and lymph nodes, though it can affect almost any part of the body including the skin, eyes, heart, and nervous system.

Sarcoma is a rare type of cancer that begins in the bones and soft tissues of the body. Although sarcomas make up only 1% of all adult cancers, they require specialized care from expert teams who understand how to treat these complex diseases.

Sarcoma metastatic is a rare and serious condition where cancer that starts in the bones or soft tissues has spread to distant parts of the body, most commonly the lungs.

Schizoaffective disorder is a mental health condition that combines symptoms of both schizophrenia and mood disorders, affecting how people think, feel, and perceive reality. This rare condition affects approximately 3 in every 1,000 people and requires specialized treatment to help individuals manage their symptoms and improve their quality of life.

Schizoaffective disorder depressive type is a complex mental health condition that combines symptoms of schizophrenia, such as hallucinations and delusions, with persistent episodes of depression. Understanding this condition is the first step toward effective treatment and better quality of life.

Schizophrenia is a serious mental health condition that changes how people think, feel, and behave, affecting approximately 1 in 345 people worldwide. While living with this condition can be challenging, effective treatments including medication and therapy can help many people manage their symptoms and lead fulfilling lives.

Schizophreniform disorder is a mental health condition that causes symptoms similar to schizophrenia—including hallucinations, delusions, and disorganized thinking—but with a critical difference: these symptoms last between one and six months, not a lifetime.

Sciatica affects about 40% of people during their lifetime, causing pain that radiates from the lower back down through the leg. While it can be debilitating, most people recover with time and self-care, though understanding its causes and treatment options is essential for effective management.

Digital ulcers are painful, open wounds that affect approximately half of all people with scleroderma at some point during their disease, significantly impacting hand function and quality of life.

Scoliosis is a condition where the spine curves sideways, often forming a C or S shape, instead of being straight. While most cases are mild and don’t cause symptoms, it can sometimes lead to back pain and uneven posture. This condition affects millions of people worldwide and is most commonly diagnosed during adolescence.

Seasonal allergies affect millions of people, turning beautiful spring days and sunny summers into times of sneezing, itchy eyes, and congestion. When trees bloom and grasses grow, your body may mistake harmless pollen for a dangerous invader, causing uncomfortable symptoms that can last for weeks or months.

Secondary progressive multiple sclerosis is a stage of MS where symptoms gradually worsen over time. It develops after relapsing-remitting MS, when the pattern of flare-ups and recovery periods changes to steady progression. While there’s no cure, treatments and lifestyle adjustments can help manage symptoms and support independence.

A seizure is a surge of abnormal electrical activity in the brain that can cause temporary changes in awareness, muscle control, behavior, and senses. Anyone can experience a seizure at any age, and understanding the different types, causes, and treatments can help you or your loved ones manage this condition more effectively.

Selective polysaccharide antibody deficiency is a condition where the immune system fails to produce protective antibodies against certain bacteria, even though overall antibody levels remain normal. This leaves affected individuals vulnerable to repeated respiratory infections caused by bacteria with sugar-coated surfaces.

Senile dementia is an outdated term that historically referred to age-related mental decline in older adults, but it incorrectly implies that serious memory and thinking problems are a normal part of aging when they are not.

Sepsis is a life-threatening medical emergency that happens when your body’s response to an infection causes damage to its own tissues and organs. It is one of the most frequent causes of death worldwide, requiring immediate medical attention and treatment to improve chances of survival.

Septic shock is the most severe stage of sepsis, a life-threatening condition that occurs when your body’s response to an infection spirals dangerously out of control, causing extremely low blood pressure and organ failure.

Serous cystadenocarcinoma is the most common form of ovarian cancer, accounting for about three out of four cases. This cancer begins in the cells that line the ovaries, fallopian tubes, or the abdomen’s inner lining, and often grows and spreads quickly.

Severe myoclonic epilepsy of infancy is a rare seizure disorder that begins in the first year of life in previously healthy babies, characterized by prolonged seizures often triggered by fever and leading to developmental challenges as the child grows.

Sexual dysfunction is a common problem that can affect anyone at any age, preventing you from feeling pleasure or satisfaction from sexual activity. While many people find it difficult to talk about, this condition is highly treatable, and understanding its causes and solutions can help you and your partner enjoy a healthier, more fulfilling sex life.

Shock is a life-threatening medical emergency that occurs when your body doesn’t have enough blood flowing through it to keep your organs working properly. Without quick treatment, shock can lead to permanent organ damage or death.

Short stature is when a child’s height falls well below what is typical for their age and sex. While most children with short stature are healthy and have no medical problems, understanding growth patterns can help families know when to seek medical advice.

Changes in the SHOX gene, located on the sex chromosomes, can lead to a range of conditions affecting growth and bone development, from mild short stature to more severe skeletal abnormalities that impact daily activities.

Short bowel syndrome is a serious condition that occurs when the body cannot absorb enough nutrients and fluids from food because part of the small intestine is missing or damaged. This rare disorder affects how your body processes the food you eat and requires specialized care to manage.

Shprintzen-Goldberg syndrome is a rare genetic disorder that affects multiple parts of the body, causing distinctive skull and facial features, skeletal problems, and developmental challenges that vary widely from person to person.

Sickle cell anaemia is a serious inherited blood disorder where red blood cells become rigid and crescent-shaped, blocking blood flow and causing pain, infections, and organ damage throughout life.

When sickle-shaped blood cells block vessels in the body, they trigger painful episodes known as sickle cell crises. These sudden events are a common complication that people with sickle cell disease face throughout their lives.

Sickle cell disease is a group of inherited blood disorders that causes red blood cells to become rigid and crescent-shaped, blocking blood flow and leading to severe pain, infections, and organ damage throughout the body.

Sinus rhythm is the normal rhythm of a healthy heart, where electrical signals begin in the sinus node and travel through the heart in a regular pattern, causing it to beat steadily at 60 to 100 beats per minute in adults.

Bacterial sinusitis is a bacterial infection that causes inflammation in the hollow spaces around your nose, often developing after a cold or viral infection that won’t go away. While most sinus infections are caused by viruses and clear up on their own, bacterial sinusitis may require different treatment to help you feel better.

Sjogren’s syndrome is a long-term autoimmune disease where the body’s immune system attacks the glands that produce moisture, leading to widespread dryness throughout the body, especially in the eyes and mouth.

Skin angiosarcoma is a rare and aggressive cancer that develops in the lining of blood vessels and lymph vessels, most commonly appearing on the head, neck, and scalp, often resembling a bruise that grows and changes over time.

Bacterial skin infections occur when harmful bacteria enter your body through breaks in the skin, and while many are mild and easily treated, some can become serious or even life-threatening if not properly managed.

Skin cancer is the most common cancer in the United States, affecting about 1 in 5 people at some point in their lives. While most types can be cured if caught early, understanding the signs, risk factors, and ways to protect yourself is essential for prevention and early detection.

Skin candida, also known as cutaneous candidiasis, is a yeast infection that affects the skin when a type of fungus called Candida grows out of control. While it commonly causes itchy, red rashes in warm, moist areas of the body, it can usually be treated effectively with antifungal medications and improved hygiene.

Skin disorders affect millions of people worldwide and include all conditions that irritate, inflame, or change the appearance of your skin, ranging from minor issues to serious health concerns.

Surgical excision is a common and effective procedure to remove skin cancers and other abnormal growths from the skin, typically performed in a doctor’s office using local anesthesia.

Skin papillomas are small, benign growths that appear on the skin, most commonly caused by a viral infection. While they are generally harmless, understanding their nature, causes, and treatment options can help you make informed decisions about managing these common skin changes.

When skin squamous cell carcinoma spreads beyond its original location to other parts of the body, it becomes a life-threatening condition that requires specialized treatment approaches and careful medical management.

Squamous cell carcinoma of the skin can return after treatment, presenting challenges for patients and healthcare providers alike. Understanding recurrence patterns, risk factors, and available treatment options is essential for managing this condition effectively.

A skin ulcer is an open wound that develops when poor blood circulation prevents injuries from healing properly, often affecting the legs, feet, back, and hips, with older people being more commonly affected.

Wrinkles are a natural part of aging that everyone experiences, appearing as lines, creases, or folds on the skin, most commonly on the face, neck, hands, and arms.