Legg-Calve-Perthes disease is a temporary condition in children in which the ball-shaped head of the thigh bone (femur), also known as the femoral head, loses its blood supply. Hence, the femoral head collapses. The body will absorb the dead bone cells and replace them with new bone cells, eventually reshaping the femoral head of the thigh bone. The femur is the large bone in the thigh, and the femoral head is the rounded ball at the end of the bone that fits into the hip socket. Legg-Calve-Perthes disease causes the hip joint to become painful and stiff for a short period of time.

The Epstein-Barr virus (EBV) can cause many different infections in humans, including mononucleosis (also called mono or the kissing disease). Many EBV infections produce mild symptoms that are similar to the common cold. However, individuals who develop mono may experience more serious symptoms, such as extreme fatigue, sore throat, enlarged lymph nodes, fever, headache, swollen tonsils, loss of appetite, soft and swollen spleen, and night sweats. EBV infections in adolescents and young adults typically cause mono.

Spina bifida is a birth defect that occurs when the tissue surrounding the spinal cord does not close properly. It is one of several disorders known as neural tube defects. Neural tube defects occur in about one out of every 1,000 births and spina bifida affects seven out of every 10,000 births. Spina bifida is the most common neural tube defect.

Roseola (also known as sixth disease, exanthema subitum, roseola infantum, baby measles, or three day fever) is a type of viral infection that is characterized by a sudden onset of high fever followed by a rash. Roseola is caused by two forms of the herpes virus. The infection can occur at any time of the year and usually is not serious.

Otitis media refers to inflammation of the middle ear. When infection occurs, the condition is called acute otitis media, or ear infection. Acute otitis media occurs when a cold, allergy, or upper respiratory infection (including the nose, sinuses, larynx or voice box, and throat) and the presence of bacteria or viruses lead to the accumulation of pus, inflammation, and mucus behind the eardrum, blocking the eustachian tube (tube leading from the ear to the throat). Earache is painful due to swelling, but usually does not require treatment. More fluid may collect and push against the eardrum, causing pain and sometimes a temporary or, in severe cases, a permanent loss of hearing. Fever generally lasts about one to two days; pain and crying may last for three to four hours. After that, most children have some pain on and off for up to four days, although young children may have pain that comes and goes for up to nine days. Adults experience similar symptoms.

Cystic fibrosis (CF), also called mucoviscidosis, is an inherited life-threatening disorder that causes severe lung damage and nutritional deficiencies.

The term cerebral palsy, or CP, refers to a neurological disorder that appears in infancy or early childhood (most commonly under 37 weeks of age) and permanently affects body movement and muscle coordination but does not worsen over time.

A fever is an increase in normal body temperature. Healthy individuals typically have a body temperature of about 98.6 degrees Fahrenheit. The body temperature fluctuates by about one degree throughout the day. However, if a person's body temperature increases more than it normally does throughout the day, he/she has a fever. A person can usually recognize when he/she has a fever because it often causes symptoms, such as chills or sweating.