Introduction
PPS is a disorder that impairs the development of the face, skin, and genitalia. Popliteal pterygium syndrome is also known as a facio-genito-popliteal syndrome, popliteal web syndrome, and congenital popliteal webbing. When they first present, patients typically have considerable webbed skin down the back of the entire leg, from the hip to the heel. In addition, the lower extremity's range of motion is restricted at all involved joints due to these enlarged skin folds, which are frequently bilaterally present (on both sides of the body) in those affected.
What Is the Cause of Popliteal Pterygium Syndrome?
Popliteal pterygium syndrome is a genetic disorder resulting from the malfunctioning of one or more genes. For example, IRF6 (interferon regulatory factor 6) gene variants, commonly called mutations, cause popliteal pterygium syndrome. An essential protein for early development is produced according to instructions from the IRF6 gene. As a transcription factor, this protein controls the expression of specific genes by binding to specific DNA (deoxyribonucleic acid) regions. In the cells that develop into tissues in the head and face, the IRF6 protein is active. Other bodily components, like the skin and genitalia, are also affected by it during development.
The impact of the transcription factor on the activity of particular genes may be altered by variations in the IRF6 gene that produces popliteal pterygium syndrome. This impairs the growth and maturation of tissues in the face, skin, and genitalia, which causes popliteal pterygium syndrome's indications and symptoms.
What Is the Inheritance Pattern of Popliteal Pterygium Syndrome?
The pattern of inheritance for this disease is autosomal dominant. In contrast to the X and Y chromosomes, autosomal genes can be located on any chromosome (sex chromosomes). Like chromosomes, genes frequently exist in pairs. Dominant refers to the fact that just one copy of the illness-causing change (pathogenic variant) on the causative gene (causal gene) is required for a person to have the condition. The earlier term "mutation" occasionally refers to a pathogenic variety.
Sometimes, a parent with a genetic disorder passes on the harmful variation to their child. Other times, there is no known family history of the condition, and the disease arises from a new harmful mutation (de novo) in the causative gene.
Probability - There is a 50 % (one in two) chance that each child of a person with an autosomal dominant disease will inherit the variation and the disease. Children who inherit a dominant variant typically develop the condition, though it may affect them less or more severely than their parents. A person may occasionally carry a pathogenic variation for an autosomal dominant disease without displaying any symptoms or signs of the illness.
What Are the Symptoms of Popliteal Pterygium Syndrome?
Some of the symptoms of popliteal pterygium syndrome are:
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Cleft Palate - When the palatine processes fail to fuse, it results in a cleft palate, which manifests as a separation of the soft and hard palate (roof of the mouth).
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Generalized Hirsutism - Almost the entire body has abnormally high hair growth.
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Joint Stiffness - Joint stiffness is the tightness felt in a joint or joints upon moving them after being inactive for a while. Over time, joint stiffness usually gets better.
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Micrognathia - Undersized mandible.
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The Thin Vermilion Border of the Upper Lip - The vermilion on the top of the upper lip appears less in height in the frontal perspective (subjective).
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Webbed Toes - Toe webbing or fusion that affects soft tissue or bone structure.
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Rib Anomalies - Abnormal rib structure.
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Abnormalities in Nails - Nail disease.
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Ankyloblepharon - One or more bands of tissue partially fuse the upper and lower eyelid borders.
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Bifid Scrotum - Cleft of the scrotum (the skin pouch that contains and protects the testicles).
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Cryptorchidism - Inguinal canal with testicles. This means that one or both testes would not have been present in the scrotum if the testis or testes could not descend through the inguinal canal.
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Fibrous Syngnathia - Alveolar ridges with complete or almost completely soft tissue union.
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Finger Syndactyly - Finger webbing or fusion involves bone structure and soft tissue.
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Hypoplastic Vaginal Majora - Underdeveloped vaginal lips.
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Lip Pits - An indentation on the lip.
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Non-midline Cleft Lip - The lateral regions of the upper lip are split instead of the midline/median area.
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Popliteal Pterygium - An occurrence of a pterygium (or pterygia) in the popliteal region (the back of the knee).
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Scoliosis - The existence of unusual lateral spine curvature.
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Small Scrotum - Underdeveloped scrotum.
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Ambiguous Genitalia - Infants with ambiguous genitalia have external genitalia that does not appear male or female.
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Choanal Atresia - The choana (the posterior nasal aperture) is absent or closed abnormally.
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Specific Learning Disability - Impairment of specific learning-related abilities, such as reading, writing, coordination, self-control, or attention. There is no connection between disability and a general lack of intelligence.
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Split Hand - A syndrome where the fingers and metacarpals, which make up the hand's middle, are absent, creating the impression of an aperture.
How Is Popliteal Pterygium Syndrome Diagnosed?
The different methods to diagnose popliteal pterygium syndrome are:
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Ultrasound - The cleft lip and palate can be seen on ultrasound as early as the first trimester when popliteal pterygium syndrome can be identified.
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Clinical Findings - A physical exam is often used to diagnose the remaining clinical findings after birth. These include the recognizable fibrous band of tissue behind the knee, the corresponding knee flexion contracture, and the symptoms of other often affected organ systems (face, genitourinary).
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Amniocentesis or Chorionic Villi Sample Testing - It is an option for patients with a family history of this condition.
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Genetic Testing - Could be employed postnatally to validate the IRF6 mutation linked to the autosomal dominant form of PPS.
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AP (Antero-Posterior) /Lateral X-Rays of the Knee - This may be taken to ensure the underlying bone architecture is not causing any loss of knee extension.
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MRI (Magnetic Resonance Imaging) Scan - Additionally, since the position of vital blood arteries and nerves can be seen during MRI scans of the knee, they may be useful in operating planning to avoid damaging them when the pterygium is surgically removed.
How Is Popliteal Pterygium Syndrome Treated?
Surgery is the mainstay of treatment for popliteal pterygium syndrome. With milder cases leading to less functional impairment, observation does play a minor role in pediatric patients. But this is uncommon. Due to the severity of joint contracture, most patients have trouble walking and doing other daily activities and instead choose to undergo surgery for treatment. To do this, the pterygium itself is surgically removed.
What Is the Procedure?
The superficial fibrous band is sliced (tenotomy) or completely removed (full resection). Following the release, it is common for nearby tissues to need lengthening or grafting to accommodate the knee joint's expanded range of motion. Other treatment options include:
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Sciatic nerve grafting.
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Local tendon lengthening.
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Once additional knee extension is attained, skin grafting may be necessary to cover the back of the leg.
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Comprehensive treatment (restoring a more typical joint alignment).
Either method aims to achieve a stable, straight knee that can be used for walking.
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Acute correction with soft tissue release and bone cutting.
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Progressive correction with an external fixator.
Conclusion
Popliteal pterygium syndrome is an uncommon condition that causes a variety of birth abnormalities. Most of the time, phenotypic traits are used to make a clinical diagnosis. For example, early surgical removal of the fibrous web and a Z-plasty in succession allows for greater knee flexion correction and improves outcomes. In addition, correcting facial deformities improves a child's appearance.
