Popliteal pterygium syndrome
Encyclopedia
Popliteal pterygium syndrome (PPS) is an inherited
condition affecting the face
, limbs
, and genitalia. The syndrome
goes by a number of names including the popliteal web syndrome and, more inclusively, the facio-genito-popliteal syndrome. The term PPS was coined by Gorlin et al.. in 1968 on the basis of the most unusual anomaly, the popliteal
pterygium
(a web behind the knee
).
of PPS are highly variable, but include the following:
of PPS has been made in several ethnic groups, including Caucasian
, Japan
ese, and sub-Saharan African. Males and females are equally likely to suffer from the syndrome. Since the disorder is very rare, its incidence rate is difficult to estimate, but is less than 1 in 10,000.
The genetic locus
for PPS was localized to chromosome 1 in 1999.
The disorder is inherited in an autosomal
dominant manner and is due to mutation
of the IRF6
gene
. Most reported cases are sporadic; advanced parental age
is found in a number of these cases, suggesting new mutations.
The term PPS has also been used for two rare autosomal recessive
ly inherited conditions: Lethal PPS and PPS with Ectodermal Dysplasia. Although both conditions feature a cleft lip/palate, syngnathia
, and popliteal
pterygium
, they are clinically distinguishable from the autosomal dominant case. Lethal PPS is differentiated by microcephaly
, corneal aplasia
, ectropion
, bony fusions, hypoplastic
nose
and absent thumb
s, while PPS with Ectodermal Dysplasia is differentiated by wool
ly hair
, brittle nails, ectoderm
al anomalies, and fissure of the sacral
vertebrae.
(VDWS) and popliteal pterygium syndrome (PPS) are allelic
variants of the same condition; that is, they are caused by different mutations of the same gene. PPS includes all the features of VDWS, plus popliteal pterygium, syngnathia, distinct toe/nail abnormality, syndactyly
, and genito-urinary malformations.
Heredity
Heredity is the passing of traits to offspring . This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism. Through heredity, variations exhibited by individuals can accumulate and cause some species to evolve...
condition affecting the face
Face
The face is a central sense organ complex, for those animals that have one, normally on the ventral surface of the head, and can, depending on the definition in the human case, include the hair, forehead, eyebrow, eyelashes, eyes, nose, ears, cheeks, mouth, lips, philtrum, temple, teeth, skin, and...
, limbs
Limb (anatomy)
A limb is a jointed, or prehensile , appendage of the human or other animal body....
, and genitalia. The syndrome
Syndrome
In medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms , phenomena or characteristics that often occur together, so that the presence of one or more features alerts the physician to the possible presence of the others...
goes by a number of names including the popliteal web syndrome and, more inclusively, the facio-genito-popliteal syndrome. The term PPS was coined by Gorlin et al.. in 1968 on the basis of the most unusual anomaly, the popliteal
Popliteal
Popliteal refers to anatomical structures located in the back of the knee:*Popliteal artery*Popliteal vein*Popliteal fossa*Popliteal lymph nodes*Popliteal nerves*Popliteal pterygium...
pterygium
Pterygium
Pterygium most often refers to a benign growth of the conjunctiva. A pterygium commonly grows from the nasal side of the sclera. It is usually present in the palpebral fissure. It is associated with, and thought to be caused by ultraviolet-light exposure , low humidity, and dust...
(a web behind the knee
Knee
The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...
).
Clinical features
Clinical expressionsMedical sign
A medical sign is an objective indication of some medical fact or characteristic that may be detected by a physician during a physical examination of a patient....
of PPS are highly variable, but include the following:
- LimbLimb (anatomy)A limb is a jointed, or prehensile , appendage of the human or other animal body....
findings: an extensive web running from behind the knee down to the heelHeelIn human anatomy, the heel is the prominence at the posterior end of the foot. It is based on the projection of one bone, the calcaneus or heel bone, behind the articulation of the bones of the lower leg.- Human anatomy :...
(90%), malformed toenails, and webbed toes. - FacialFaceThe face is a central sense organ complex, for those animals that have one, normally on the ventral surface of the head, and can, depending on the definition in the human case, include the hair, forehead, eyebrow, eyelashes, eyes, nose, ears, cheeks, mouth, lips, philtrum, temple, teeth, skin, and...
findings: cleft palate with or without cleft lip (75%), pits in the lower lipLipLips are a visible body part at the mouth of humans and many animals. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech...
(40%), and fibrous bands in the mouthMouthThe mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
known as syngnathiaSyngnathiaSyngnathia is a congenital adhesion of the maxilla and mandible by fibrous bands....
(25%). - Genital findings (50%): hypoplasiaHypoplasiaHypoplasia is underdevelopment or incomplete development of a tissue or organ. Although the term is not always used precisely, it properly refers to an inadequate or below-normal number of cells. Hypoplasia is similar to aplasia, but less severe. It is technically not the opposite of hyperplasia...
of the labia majoraLabia majoraThe labia majora are two prominent longitudinal cutaneous folds that extend downward and backward from the mons pubis to the perineum and form the lateral boundaries of the pudendal cleft, which contains the labia minora, interlabial sulci, clitoral hood, clitoral glans, frenulum clitoridis, the...
, malformation of the scrotumScrotumIn some male mammals the scrotum is a dual-chambered protuberance of skin and muscle containing the testicles and divided by a septum. It is an extension of the perineum, and is located between the penis and anus. In humans and some other mammals, the base of the scrotum becomes covered with curly...
, and cryptorchidismCryptorchidismCryptorchidism is the absence of one or both testes from the scrotum. It is the most common birth defect regarding male genitalia. In unique cases, cryptorchidism can develop later in life, often as late as young adulthood. About 3% of full-term and 30% of premature infant boys are born with at...
.
Epidemiology
The diagnosisDiagnosis
Diagnosis is the identification of the nature and cause of anything. Diagnosis is used in many different disciplines with variations in the use of logics, analytics, and experience to determine the cause and effect relationships...
of PPS has been made in several ethnic groups, including Caucasian
Caucasian race
The term Caucasian race has been used to denote the general physical type of some or all of the populations of Europe, North Africa, the Horn of Africa, Western Asia , Central Asia and South Asia...
, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese, and sub-Saharan African. Males and females are equally likely to suffer from the syndrome. Since the disorder is very rare, its incidence rate is difficult to estimate, but is less than 1 in 10,000.
Genetics
Locus (genetics)
In the fields of genetics and genetic computation, a locus is the specific location of a gene or DNA sequence on a chromosome. A variant of the DNA sequence at a given locus is called an allele. The ordered list of loci known for a particular genome is called a genetic map...
for PPS was localized to chromosome 1 in 1999.
The disorder is inherited in an autosomal
Autosome
An autosome is a chromosome that is not a sex chromosome, or allosome; that is to say, there is an equal number of copies of the chromosome in males and females. For example, in humans, there are 22 pairs of autosomes. In addition to autosomes, there are sex chromosomes, to be specific: X and Y...
dominant manner and is due to mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
of the IRF6
IRF6
Interferon regulatory factor 6 also known as IRF6 is a protein that in humans is encoded by the IRF6 gene.-Function:This gene encodes a member of the interferon regulatory transcription factor family...
gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
. Most reported cases are sporadic; advanced parental age
Senescence
Senescence or biological aging is the change in the biology of an organism as it ages after its maturity. Such changes range from those affecting its cells and their function to those affecting the whole organism...
is found in a number of these cases, suggesting new mutations.
The term PPS has also been used for two rare autosomal recessive
Recessive
In genetics, the term "recessive gene" refers to an allele that causes a phenotype that is only seen in a homozygous genotype and never in a heterozygous genotype. Every person has two copies of every gene on autosomal chromosomes, one from mother and one from father...
ly inherited conditions: Lethal PPS and PPS with Ectodermal Dysplasia. Although both conditions feature a cleft lip/palate, syngnathia
Syngnathia
Syngnathia is a congenital adhesion of the maxilla and mandible by fibrous bands....
, and popliteal
Popliteal
Popliteal refers to anatomical structures located in the back of the knee:*Popliteal artery*Popliteal vein*Popliteal fossa*Popliteal lymph nodes*Popliteal nerves*Popliteal pterygium...
pterygium
Pterygium
Pterygium most often refers to a benign growth of the conjunctiva. A pterygium commonly grows from the nasal side of the sclera. It is usually present in the palpebral fissure. It is associated with, and thought to be caused by ultraviolet-light exposure , low humidity, and dust...
, they are clinically distinguishable from the autosomal dominant case. Lethal PPS is differentiated by microcephaly
Microcephaly
Microcephaly is a neurodevelopmental disorder in which the circumference of the head is more than two standard deviations smaller than average for the person's age and sex. Microcephaly may be congenital or it may develop in the first few years of life...
, corneal aplasia
Aplasia
Aplasia is defined in general as "defective development or congenital absence of an organ or tissue." In the field of hematology, the term refers to "incomplete, retarded, or defective development, or cessation of the usual regenerative process."-Examples:*Acquired pure red cell aplasia*Aplasia...
, ectropion
Ectropion
Ectropion is a medical condition in which the lower eyelid turns outwards. It is one of the notable aspects of newborns exhibiting congenital Harlequin type ichthyosis, but ectropion can occur due to any weakening of tissue of the lower eyelid. The condition can be repaired surgically...
, bony fusions, hypoplastic
Hypoplasia
Hypoplasia is underdevelopment or incomplete development of a tissue or organ. Although the term is not always used precisely, it properly refers to an inadequate or below-normal number of cells. Hypoplasia is similar to aplasia, but less severe. It is technically not the opposite of hyperplasia...
nose
Human nose
The visible part of the human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the ethmoid bone and the nasal septum, which consists mostly of cartilage and which separates the nostrils...
and absent thumb
Thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
s, while PPS with Ectodermal Dysplasia is differentiated by wool
Wool
Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits....
ly hair
Hair
Hair is a filamentous biomaterial, that grows from follicles found in the dermis. Found exclusively in mammals, hair is one of the defining characteristics of the mammalian class....
, brittle nails, ectoderm
Ectoderm
The "ectoderm" is one of the three primary germ cell layers in the very early embryo. The other two layers are the mesoderm and endoderm , with the ectoderm as the most exterior layer...
al anomalies, and fissure of the sacral
Sacral
Sacral may refer to:*sacred*sacrum...
vertebrae.
Relationship to Van der Woude syndrome
Van der Woude syndromeVan der Woude syndrome
Van Der Woude syndrome is a genetic disorder and congenital malformation. People with VDWS have cleft lip with or without cleft palate, pits or mucous cysts on the lower lip, hypodontia, a hypernasal voice, cleft or bifid uvula, syngnathia, narrow high arched palate, and ankyloglossia...
(VDWS) and popliteal pterygium syndrome (PPS) are allelic
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
variants of the same condition; that is, they are caused by different mutations of the same gene. PPS includes all the features of VDWS, plus popliteal pterygium, syngnathia, distinct toe/nail abnormality, syndactyly
Syndactyly
Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and kangaroo, but is an unusual condition in humans.-Classification:...
, and genito-urinary malformations.