Acanthosis nigricans is a skin condition characterized by areas of dark, velvety discoloration in body folds and creases. The affected skin can become thickened. Most often, acanthosis nigricans affects your armpits, groin and neck. The sk...

Alkaptonuria is an inherited condition that causes urine to turn black when exposed to air. Ochronosis, a buildup of dark pigment in connective tissues such as cartilage and skin, is also characteristic of the disorder. This blue-black pigmentatio...

What is arsenic? Arsenic is a grey-appearing chemical element (atomic number 33, symbol As in the periodic table) also termed a metalloid. Arsenic can exist in a metallic state in three forms (yellow, black, and gray; with gray predominati...

Bile duct cancer, also called cholangiocarcinoma, is when unusual cells grow out of control inside your bile ducts. Those are thin tubes about 4 to 5 inches long that move a fluid called bile from your liver to your gallbladder and small intestine...

Bile duct cancer, also called cholangiocarcinoma, is when unusual cells grow out of control inside your bile ducts. Those are thin tubes about 4 to 5 inches long that move a fluid called bile from your liver to your gallbladder and small intestine...

Hairy tongue is an uncommon, benign condition that is also known as black hairy tongue or lingua nigra. It is characterized by abnormal elongation and blackish or dark brownish discoloration or "staining" of the thread-like elevations (filiform pa...

Bloom syndrome is a rare genetic disorder characterized by short stature; increased sensitivity to light (photosensitivity); multiple small dilated blood vessels on the face (facial telangiectasia), often resembling a butterfly in shape; immune de...

Blue rubber bleb nevus syndrome (BRBNS) is a rare blood vessel (vascular) disorder that affects the skin and internal organs of the body. Multiple distinctive skin lesions are usually characteristic of this disorder and are often present at birth ...

Bullous pemphigoid is an uncommon skin disease characterized by tense blisters on the surface of the skin. Occasionally, the inner lining tissue of the mouth, nasal passages, or conjunctivae of the eyes (mucous membrane tissue) can be involved. Th...

Central serous chorioretinopathy (CSC) is a disorder of the eye in which fluid accumulates beneath the retina, causing it to detach from the back of the eye. This can lead to blurred vision, distortion of vision, and blind spots. CSC is usually ca...

Chanarin Dorfman syndrome is a rare hereditary disorder of fat (lipid) metabolism. It is characterized by scaly skin (ichthyosis), degeneration of the muscles (myopathy), and abnormal white blood cells with small spaces (vacuoles) filled with fat ...

Chilblains (CHILL-blayns) are the painful inflammation of small blood vessels in your skin that occur in response to repeated exposure to cold but not freezing air. Also known as pernio, chilblains can cause itching, red patches, swelling and blis...

Best vitelliform macular dystrophy is an autosomal dominant genetic form of macular degeneration that usually begins in childhood or adolescence and slowly progresses to affect central vision. The age of onset and severity of vision loss are highl...

Autosomal dominant interstitial kidney disease describes a group of diseases affecting solely the proper function of the kidney and having the following characteristics: They are inherited in an autosomal dominant manner; kidney disease develops, ...

An ectopic pregnancy is a pregnancy located outside the inner lining of the uterus. Risk factors for ectopic pregnancy include previous ectopic pregnancies and conditions (surgery, infection) that disrupt the normal anatomy of the F...

"Eye floaters" are deposits or condensation in the vitreous jelly of the eye. People use the term eye floaters to describe seeing floating spots within their vision when they look around. Eye floaters may be present in only one eye or both eyes....

Fabry disease is caused by the lack of or faulty enzyme needed to metabolize lipids, fat-like substances that include oils, waxes, and fatty acids. The enzyme is known as ceramide trihexosidase, also called alpha-galactosidase-A. A mutation in the...

Fox-Fordyce disease is a rare skin disorder that primarily affects women. The disorder is characterized by intense itching especially in the underarm area, the pubic area and around the nipples. In Fox-Fordyce disease abnormalities affecting the a...

Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency (G6PDD) is an inherited, sex-linked, metabolic disorder characterized by an enzyme defect that leads to the breakdown of red blood cells (hemolysis) upon exposure to stresses associated with some...

Though ulcers often heal on their own, you shouldn't ignore their warning signs. If not properly treated, ulcers can lead to serious health problems, including: Bleeding Perforation (a hole through the wall of the stomach)...

Fabry disease is a rare genetic disorder of fat (lipid) metabolism characterized by a deficiency of the enzyme alpha-galactosidase A (previously known as ceramide trihexosidase). The disorder belongs to a group of diseases known as lysosomal stora...

Hepatitis A is a highly contagious liver infection caused by the hepatitis A virus. It is typically spread through contaminated food or water, or through close contact with an infected person. Symptoms of hepatitis A can include fever, fatigue, lo...

Hepatitis B is a viral infection that attacks the liver and can cause both acute and chronic disease. The virus is transmitted through contact with the blood or other body fluids of an infected person. Hepatitis B can be a mild illness lasting a f...

Hepatitis C is a viral infection that causes liver inflammation, sometimes leading to serious liver damage. The hepatitis C virus (HCV) is spread through contact with infected blood, most commonly through sharing needles or other equipment used to...

Alkaptonuria is a rare genetic metabolic disorder characterized by the accumulation of homogentisic acid in the body. Affected individuals lack enough functional levels of an enzyme required to breakdown homogentisic acid. Affected individuals may...

Chanarin Dorfman syndrome is a rare hereditary disorder of fat (lipid) metabolism. It is characterized by scaly skin (ichthyosis), degeneration of the muscles (myopathy), and abnormal white blood cells with small spaces (vacuoles) filled with fat ...

Chanarin Dorfman syndrome is a rare hereditary disorder of fat (lipid) metabolism. It is characterized by scaly skin (ichthyosis), degeneration of the muscles (myopathy), and abnormal white blood cells with small spaces (vacuoles) filled with fat ...

Incontinentia Pigmenti (IP) is a rare genetic dermatological disorder affecting the skin, hair, teeth, and central nervous system. Progressive skin changes occur in four stages, the first of which appear in early infancy or can be present at birth...

Juvenile Macular Dystrophy (JMD) is a rare, inherited eye disorder that affects the macula, the part of the eye responsible for central vision. It is characterized by progressive vision loss, usually beginning in childhood or adolescence. Symptoms...

Madelung's disease is a disorder of fat metabolism (lipid storage) that results in an unusual accumulation of fat deposits around the neck and shoulder areas. Adult alcoholic males are most often affected, although women and those who do not drink...

Drug-induced liver diseases are diseases of the liver that are caused by physician-prescribed medications, over-the-counter medications, vitamins, hormones, herbs, illicit ("recreational") drugs, and environmental toxins. What is the liver...

Macular hole is a small break in the macula, a small spot near the center of the retina that is responsible for sharp, central vision. Macular holes can cause blurred or distorted central vision, and if left untreated, can lead to permanent vision...

Macular pucker is a condition in which the macula, the part of the eye responsible for central vision, becomes wrinkled or distorted. It is caused by the formation of scar tissue on the macula, which can cause blurred or distorted vision. Treatmen...

Neuroblastoma is a disease in which malignant (cancer) cells form in nerve tissue of the adrenal gland, neck, chest, or spinal cord. Neuroblastoma often begins in the nerve tissue of the adrenal glands. There are two adrenal glands, one on...

Alkaptonuria is a rare genetic metabolic disorder characterized by the accumulation of homogentisic acid in the body. Affected individuals lack enough functional levels of an enzyme required to breakdown homogentisic acid. Affected individuals may...

Alkaptonuria is a rare genetic metabolic disorder characterized by the accumulation of homogentisic acid in the body. Affected individuals lack enough functional levels of an enzyme required to breakdown homogentisic acid. Affected individuals may...

X-linked ichthyosis is a genetic skin disorder that affects males. It is an inborn error of metabolism characterized by a deficiency of the enzyme steroid sulfatase. Under normal conditions, this enzyme breaks down (metabolizes) cholesterol sulfat...

X-linked ichthyosis is a genetic skin disorder that affects males. It is an inborn error of metabolism characterized by a deficiency of the enzyme steroid sulfatase. Under normal conditions, this enzyme breaks down (metabolizes) cholesterol sulfat...

Tetracycline staining refers to a discoloration of the teeth caused by the use of tetracycline antibiotics during tooth development. Tetracycline antibiotics can bind to calcium ions in developing teeth, leading to a yellow or grayish-brown discol...

Tinea versicolor is a common fungal infection of the skin. The fungus interferes with the normal pigmentation of the skin, resulting in small, discolored patches. These patches may be lighter or darker in color than the surrounding skin and most c...

Peptic ulcers are open sores that develop on the inside lining of your stomach a...

Gilbert syndrome is a mild genetic liver disorder in which the body cannot properly process bilirubin, a yellowish waste product that is formed when old or worn out red blood cells are broken down (hemolysis). Individuals with Gilbert syndrome hav...

Porphyria cutanea tarda (PCT) is a type of porphyria in which affected individuals are sensitive to sunlight. Exposed skin shows abnormalities that range from slight fragility of the skin to persistent scarring and disfiguration. Due to fragility ...