Phenylketonuria 391

cat breeds can become infected with the parasite; cats become infected by killing and eating small rodents. Most children contract the disease not from cats, however, but from raw meat. The meat becomes infected because sheep and cattle graze in pastures contaminated by cats. The disease, which rarely causes symptoms, can be treated with antibacterial drugs.

pharyngitis An acute inflammation of the part of the throat between the tonsils and the larynx (the pharynx). Especially sore throats should be reported to a physician, who may take a throat culture and prescribe antibiotics.


The illness most often is caused by a viral infection, although it also may be due to a bacterial infection. It is a common symptom of a cold or influenza, of

MONONUCLEOSIS or SCARLET FEVER. DIPHTHERIA is a rare cause of pharyngitis.


In addition to the sore throat, there may be pain when swallowing together with a slight fever, earache, and tender, swollen lymph nodes in the neck. In very severe cases the fever may be quite high, and the soft palate and throat may swell so that breathing becomes difficult. Extensive swelling and fluid buildup in the larynx can be life threatening.


Warm salt water gargles can help ease symptoms. If the inflammation is bacterial, antibiotics can be prescribed.

phenylketonuria (PKU) An inherited metabolic disease (one of the many possible inborn errors of metabolism) that leads to mental retardation and other developmental disabilities if untreated in infancy. In phenylketonuria (PKU), an amino acid called phenylalanine builds up in the bloodstream, causing brain damage. Infants with untreated PKU appear to develop typically for the first few months of life, but by 12 months of age most babies will have a significant developmental delay and will be diagnosed with mental retardation.

PKU is inherited as a single-gene disorder, which is a condition caused by a mutant or abnormal gene. It is an autosomal recessive disorder, which means that each parent of a child with PKU carries one defective gene for the disorder and one normal gene. In a recessive condition, an individual must have two defective genes in order to have the disorder. Individuals with only one copy of a defective gene are called "carriers," show no symptoms of having the disease, and usually remain unaware of their status until they have an affected child. In order for a child to inherit PKU, both parents must be PKU carriers. When this occurs, there is a one in four chance of their producing an affected child with each pregnancy. Boys and girls are equally at risk of inheriting this disorder.

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