Achondroplasia is a bone growth disorder that causes short-limb dwarfism, where the upper ends of one’s legs and arms remain shorter than the lower ends. The average height of patients is below four feet, one inch for females and four feet, four inches for males.

Also called skin tags, acrochordons are skin-colored non-cancerous growths. They usually look like a skin tissue cluster branching from a tiny stem. At times, they are darker and resemble a raised mole.

Actinic keratosis, or solar keratosis, is a condition that causes lesions or patches on the skin’s outer layer due to prolonged exposure to UV rays from sunlight. It is common among individuals over 40 and can lead to skin cancer if left untreated.

Acute flaccid myelitis is a rare but severe condition that causes spinal cord damage. This condition can lead to sudden legs or arms weakening. In addition, it can also result in loss of muscle reflexes and tone.

Also called adrenal insufficiency, Addison’s disease is a rare illness that develops when the body does not yield certain hormones in adequate quantities. The adrenal glands make too little cortisol and aldosterone in those with Addison’s disease.

A brain aneurysm is a weak spot in a blood vessel in the brain, causing it to bulge. This bulge in the vessel can exert pressure on surrounding tissues and potentially lead to a rupture, resulting in serious complications.

Adenoid cystic carcinoma is a rare form of cancer that develops in the glands that produce saliva. The glands are located under the tongue and on each side of the jaw below the jawbone.

Agoraphobia is an anxiety disorder where a person develops an irrational and extreme fear of being unable to escape an embarrassing or difficult situation. Some believe it is a fear of leaving the house, but it is much more complex.