Opioid addiction is a long-lasting (chronic) disease that can cause major health, social, and economic problems. Opioids are a class of drugs that act in the nervous system to produce feelings of pleasure and pain relief. Some opioids are legally pre READ MORE

Opitz G/BBB syndrome is a genetic condition that causes several abnormalities along the midline of the body. "G/BBB" represents the first letters of the last names of the families first diagnosed with this disorder and "Opitz" is the last name of the READ MORE

Optic atrophy type 1 is a condition that often causes slowly worsening vision, usually beginning in childhood. People with optic atrophy type 1 typically experience a narrowing of their field of vision (tunnel vision). Affected individuals gradually READ MORE

Oral-facial-digital syndrome is actually a group of related conditions that affect the development of the oral cavity (the mouth and teeth), facial features, and digits (fingers and toes). Researchers have identified at least 13 potential forms of or READ MORE

Orthostatic hypotension is a drop in blood pressure that occurs when moving from a lying-down (supine) position to a standing (upright) position. The word "orthostasis" means to stand up, so the condition is defined as low blood pressure (hypotension READ MORE

Osteoarthritis is a common disease of the joints that primarily occurs in older adults. This condition is characterized by the breakdown of cartilage, the tough but flexible tissue that covers the ends of the bones at the joints and allows smooth joi READ MORE

Osteogenesis imperfecta (OI) is a group of genetic disorders that mainly affect the bones. The term "osteogenesis imperfecta" means imperfect bone formation. People with this condition have bones that break (fracture) easily, often from mild trauma o READ MORE

Osteoglophonic dysplasia is a condition characterized by abnormal bone growth that leads to severe head and face (craniofacial) abnormalities, short stature, and other features. The term osteoglophonic refers to the bones (osteo-) having distinctive READ MORE

Osteopetrosis is a bone disease that makes bone tissue abnormally compact and dense and also prone to breakage (fracture). Researchers have described several major types of osteopetrosis, which are usually distinguished by their pattern of inheritanc READ MORE

Osteoporosis-pseudoglioma syndrome is a rare condition characterized by severe thinning of the bones (osteoporosis) and eye abnormalities that lead to vision loss. In people with this condition, osteoporosis is usually recognized in early childhood. READ MORE

Otopalatodigital syndrome type 1 is a disorder primarily involving abnormalities in skeletal development. It is a member of a group of related conditions called otopalatodigital spectrum disorders, which also includes otopalatodigital syndrome type 2 READ MORE

Otopalatodigital syndrome type 2 is a disorder primarily involving abnormalities in skeletal development. It is a member of a group of related conditions called otopalatodigital spectrum disorders, which also includes otopalatodigital syndrome type 1 READ MORE