P–R

Patau’s syndrome An AUTOSOMAL TRISOMYdisor-
der that results from a REPLICATION ERRORduring
cell division in which a GAMETE(sex cell) ends up
with two copies of CHROMOSOME13 instead of the
normal single copy (as haploid cells, gametes con-
tain one-half the complement of chromosomes).
At CONCEPTIONthe ZYGOTEthus ends up with three
instead of the normal two copies of chromosome
13, which ultimately produces multiple and life-
threatening congenital anomalies. When Patau’s
syndrome occurs as a complete trisomy disorder
(all cells carry the extra chromosome), the anom-
alies are so severe that the disorder often is lethal
well before birth. Occasionally Patau’s syndrome
occurs as a mosaic disorder (some but not all cells
contain the extra chromosome 13), which typi-
cally produces milder though nonetheless signifi-
cant symptoms. Patau’s syndrome occurs in about
1 in 10,000 live births in the United States.

CONGENITAL ANOMALIES

CHARACTERISTIC OF PATAU’S SYNDROME

atrial septal defect (ASD) CLEFT PALATE/CLEFT PALATE
malformed KIDNEYS AND LIP
malformed or absent eyes malformed KIDNEYS
malformed or absent NOSE microcephaly (small head
multiple hernia and BRAIN)
patent ductus arteriosus polycystic kidneys
(PDA) POLYDACTYLY
ventricular septal defect (VSD) Vextrocardia (HEARTon right
side of chest)

Children born with Patau’s syndrome have
severe and complex physical deformities involving
multiple organ systems that require extensive
medical care from the time of birth. Most also
have severe developmental delays and intellectual
impairment arising from malformations affecting

the BRAINand NERVOUS SYSTEM. KARYOTYPEconfirms

the diagnosis. It is rare for a child who has Patau’s

syndrome to survive beyond early childhood;

there are no documented survivals to adulthood.

Ongoing medical care to accommodate physical

anomalies and developmental support to achieve

optimal learning potential provide the child who

survives the best possible QUALITY OF LIFE.

See also AUTOSOME; CHROMOSOME DISORDERS; CON-

GENITAL ANOMALY; CONGENITAL HEART DISEASE; DOWN

SYNDROME; EDWARDS SYNDROME; ETHICAL ISSUES IN

GENETICS AND MOLECULAR MEDICINE; GENETIC SCREEN-

ING; INHERITANCE PATTERNS; MOSAICISM; POLYCYSTIC KID-

NEY DISEASE.

phenotype The outward presentation, or fea-

tures, of an individual’s GENOTYPE(genetic compo-

sition). The phenotype is the construction and

operation that results from implementation of the

genotype, much as a house is the outcome of a

building contractor’s implementation of an archi-

tect’s blueprints. A phenotype consists of such

obvious characteristics as EYEcolor and HAIRpat-

terns as well as less apparent traits such as BLOOD

TYPEand proclivity for health or certain diseases.

The genotype for lipid METABOLISM, for example,

may support effective use of lipids within the body

(supporting health) or the tendency for high levels

of lipids to accumulate in the BLOOD(increasing

the risk for CARDIOVASCULAR DISEASE[CVD]).

See also ALLELE; ALOPECIA; CELL STRUCTURE AND

FUNCTION; FAMILY MEDICAL PEDIGREE; VARIATION.

phenylketonuria (PKU) An inherited genetic

disorder in which the enzyme phenylalanine

hydroxylase is missing or severely deficient, pre-

venting the METABOLISMof the essential amino acid

(one the body must acquire from dietary sources)

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