Popliteal pterygium syndrome

DiseaseDisorder infobox
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Caption =
ICD10 = ICD10|Q|79|8|q|65
(EUROCAT Q79.82)
ICD9 = ICD9|756.89
ICDO =
OMIM = 119500
DiseasesDB = 33503
MedlinePlus =
eMedicineSubj =
eMedicineTopic =

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). [ [http://pediatrics.aappublications.org/cgi/content/abstract/41/2/503 pediatrics] ]

Clinical Features

Clinical expressions of PPS are highly variable, but include the following: [ [http://www.medterms.com/script/main/art.asp?articlekey=5001 medterms.com] ] [J Pediatr Orthop B 2004, 13:197-201.]

* Limb findings: an extensive web running from behind the knee down to the heel (90%), malformed toenails, and webbed toes.
* Facial findings: cleft palate with or without cleft lip (75%), pits in the lower lip (40%), and fibrous bands in the mouth known as syngnathia (25%).
* Genital findings (50%): hypoplasia of the labia majora, malformation of the scrotum, and cryptorchidism.

Epidemiology

The diagnosis of PPS has been made in several ethnic groups, including Caucasian, Japanese, 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. [J Med Genet 1990; 27:320-6.]

Genetics

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 recessively 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 thumbs, while PPS with Ectodermal Dysplasia is differentiated by woolly hair, brittle nails, ectodermal anomalies, and fissure of the sacral vertebrae. [Brit J Oral Maxillofacial Surg 1998; 36:138-40.]

Relationship to Van der Woude syndrome

Van der Woude syndrome (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. [Hong Kong Med J 2004; 10(5):331-6.]

References