Obstructive sleep apnea
Blockage of the breathing passages for 10 seconds or more during sleep; marked by the child's not being able to breathe even when trying to; commonly caused by enlarged tonsils and/or adenoids; can cause significant problems if not treated; treatment usually involves removing the adenoids and tonsils.

Osteomyelitis
Inflammation of the bone; usually caused by a bacterial infection; bacterial osteomyelitis requires treatment with antibiotics.

Otitis externa
Swimmer's ear; inflammation of the outer ear canal; typically caused by a bacterial infection.

Otitis media
Inflammation of the middle ear; typically caused by a bacterial or viral infection.

P

Pediculosis
See Lice.

Pelvic inflammatory disease (PID)
Infection of the female genital tract; caused by infections like chlamydia and gonorrhea in sexually active girls and women; can cause infertility if not treated promptly with antibiotics.

Peptic ulcer
An area of the stomach where the lining is raw, inflamed, and irritated by stomach acids; usually caused by the bacterium, Helicobacter pylori; less common in children than adults; can be treated with antibiotics.

Peritonitis
Inflammation of the membrane lining the abdomen and pelvis; usually caused by a bacterial infection resulting from a rupture of the intestines (as in a ruptured appendix).

Pertussis
Whooping cough; a vaccine-preventable, contagious respiratory disease marked by symptoms of a common cold followed by spasms of forceful coughing which can last weeks to months and result in serious complications; caused by the bacterium, Bordatella pertussis; treatment with antibiotics helps prevent spread to others, but usually does not help cure the affected child unless given very early; whooping cough can be prevented with routine immunization (the "aP" in DTaP vaccine).

Petechiae
Pinpoint sized, non-raised, round, dark red spots just below the skin; don't go away when the skin is pressed and released; can be due bleeding problems, trauma or infections.

Pharyngitis
Sore throat; inflammation of the throat generally caused by a viral or bacterial infection.

Phimosis
Inability to pull the foreskin back over the head of the penis; can be treated by circumcision, but resolves by itself in most boys by age 3 years.

Pinkeye
See conjunctivitis.

Pinworms
A common intestinal infection characterized mainly by itching around the anus; caused by tiny white worms (Enterobius vermicularis); can be treated with oral medication.

Platelet
A very small fragment of a larger blood cell called a megakaryocyte; important in blood clotting.

Pneumococcus
Streptococcus pneumoniae; a vaccine-preventable bacterium capable of causing infections in the bloodstream, lungs, ears or nervous system; typically marked by rapid onset and high fever; usually responds well to antibiotics, but serious infections may be fatal; a new vaccine recently has been approved for routine use in infants.

Pneumonia
Inflammation of the lung tissue causing symptoms including fever, cough, fast breathing and, sometimes, shortness of breath; usually caused by a bacterial or viral infection.

Polio
Poliomyelitis; a vaccine-preventable, contagious viral infection that can attack the nervous system and result in varying degrees of permanent weakness and paralysis; is extremely rare in developed countries because of successful immunization programs with oral polio vaccine (OPV) or inactivated polio vaccine (IPV); there is no specific treatment, only supportive care.

Proteinuria
Increased concentration of protein in the urine; seen in nephrotic syndrome, chronic kidney infections and other kidney disorders.

Psoriasis
A chronic skin condition marked by recurrent red itchy patches covered with silvery scales and plaques; most commonly seen on elbows, knees, scalp and trunk; cause is unknown; there is no cure, but symptomatic treatment helps.

Purpura
Purplish spots in the skin caused by hemorrhage; can be caused by a variety of conditions, including low platelet count, viral infections, trauma or autoimmune disorders such as Henoch-Schoenlein purpura.

Pyelonephritis
A bacterial infection of the kidney marked by fever, fatigue, nausea, vomiting and flank pain; treatable with antibiotics.

Pyloric stenosis
An obstruction of the stomach outlet to the intestines caused by an enlargement of the circular muscle (pylorus) at the far end of the stomach; typically begins with forceful (projectile) vomiting around three weeks of age; often requires surgical repair.

Q

Quadriplegia
Paralysis of the body from the neck down, including both arms and both legs.

R

Reactive airway disease
Asthma.

Respiratory syncytial virus (RSV)
A highly contagious respiratory virus that is the primary cause of bronchiolitis in infants.

Rheumatic fever
A condition marked by involvement of the heart, blood vessels, joints, nervous system and/or skin; follows group A streptococcal upper respiratory infections, particularly strep throat; can result in permanent heart valve damage; treatment with antibiotics (usually penicillin) centers around preventing further streptococcal infections.

Rhinitis
Inflammation of the mucous membranes of the nose, causing runny nose and nasal stuffiness; usually caused by viral upper respiratory infections or allergies.

Rickets
A disease caused by vitamin D deficiency marked by abnormalities of bone, growth and muscle function; usually caused by insufficient vitamin D intake and/or limited exposure to sunlight.

Ringworm
A fungal (not worm) infection of the skin causing itchy, pinkish, ring-shaped patches, often with a pale central area; transmitted by direct contact; treatable with at least four weeks of medication.

Roseola
Roseola infantum; exanthem subitum; sixth disease; a mild viral infection of infants and toddlers marked by three or four days of very high fever and then, after the fever breaks, the development of a red rash; caused by herpesvirus 6; resolves without treatment, but febrile seizures may occur during the febrile stage of the infection.

Rotavirus
A group of viruses that is a major cause of vomiting and diarrhea in children; in temperate climates, usually occurs in winter months.

Rubella (German measles)
A vaccine-preventable viral infection marked by mild upper respiratory symptoms, a red rash and generalized lymphadenopathy; a cause of serious birth defects if contracted early in pregnancy; prevented by routine immunization with rubella vaccine (the "R" in MMR vaccine).