In medicine, sclerosis (also spelled sclerosus in the names of a few disorders) refers to the stiffening of a structure, usually caused by a replacement of the normal organ-specific tissue with connective tissue.
- Amyotrophic lateral sclerosis, sometimes known as motor neuron disease or Lou Gehrig's disease, a progressive, incurable, usually fatal disease of motor neurons.
- Atherosclerosis, a deposit of fatty materials, such as cholesterol, in the arteries which causes hardening.
- Focal Segmental Glomerulosclerosis is a disease that attacks the kidney's filtering system (glomeruli) causing serious scarring and thus a cause of nephrotic syndrome in children and adolescents, as well as an important cause of kidney failure in adults.
- Hippocampal sclerosis, a brain damage often seen in individuals with temporal lobe epilepsy.
- Lichen sclerosus, a disease hardening and connecting flesh of the vagina of women and the penis of men. An autoimmune disorder.
- Liver sclerosis is a common misspelling of cirrhosis of the liver.
- Multiple sclerosis, or Focal Sclerosis, is a central nervous system disease which affects coordination.
- Osteosclerosis, a condition where the bone density is significantly increased.
- Otosclerosis, a disease of the ears.
- Systemic sclerosis (progressive systemic scleroderma), a rare, chronic disease which affects the skin, and in some cases also blood vessels and internal organs.
- Tuberous sclerosis, a rare genetic disease which affects multiple systems.
- Primary sclerosing cholangitis, a hardening of the bile duct by scarring and repeated inflammation.
- Primary lateral sclerosis, progressive muscle weakness in the voluntary muscles.