Frontonasal dysplasia

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Frontonasal dysplasia
Other namesmedian cleft face syndrome, frontonasal dysostosis, frontonasal malformation, Tessier cleft number 0/14
Median Cleft Face Syndrome 1.jpg
Infant with frontonasal dysplasia
Specialty Medical genetics   OOjs UI icon edit-ltr-progressive.svg

Frontonasal dysplasia (FND) is a congenital malformation of the midface. [1] For the diagnosis of FND, a patient should present at least two of the following characteristics: hypertelorism (an increased distance between the eyes), a wide nasal root, vertical midline cleft of the nose and/or upper lip, cleft of the wings of the nose, malformed nasal tip, encephalocele (an opening of the skull with protrusion of the brain) or V-shaped hair pattern on the forehead. [1] The cause of FND remains unknown. FND seems to be sporadic (random) and multiple environmental factors are suggested as possible causes for the syndrome. However, in some families multiple cases of FND were reported, which suggests a genetic cause of FND. [2] [3]

Contents

Classification

[4] There are multiple classification systems for FND. None of these classification systems have unraveled any genetic factors as the cause of FND. Yet, all of them are very valuable in determining the prognosis of an individual. In the subheadings below, the most common classifications will be explained.

Sedano classification

This is a classification based on the embryological cause of FND.

De Myer

This classification is based on the morphologic characteristics of FND, that describes a variety of phenotypes[ citation needed ]

Both of these classifications are further described in table 1. This table originates from the article ‘Acromelic frontonasal dysplasia: further delineation of a subtype with brain malformations and polydactyly (Toriello syndrome)', Verloes et al.

Table 1. Phenotypic Classifications of the face in Frontonasal Dysplasia.
DeMyer classification (slightly expanded)Characteristics
Type 1hypertelorism, cranium bifidum, median cleft nose, and cleft prolabium
Type 2hypertelorism, cranium bifidum, and cleft nose but intact prolabium and palate
Type 3hypertelorism, median cleft nose, and median cleft of notched lip
Type 4hypertelorism and median cleft nose
Each type may be then subdivided in:
Subtype athe two sides of the cleft nose are set apart
Subtype bthe two sides of the nose remain continuous. The cleft of the nose involves the nasal septum and extends to the tip of the nose
Subtype cthe cleft does not reach the tip of the nose. hypertelorism is borderline
Sedano-Jirásek classificationCharacteristics
Type Ahypertelorism, median nasal groove, and absent nasal tip
Type Bhypertelorism, median groove or cleft face, with or without lip or palate cleft
Type Chypertelorism and notching of alae nasi
Type Dhypertelorism, median groove or cleft face, with or without lip or palate cleft and notching of alae nasi

Signs and symptoms

Boy with frontonasal dysplasia, showing hypertelorism Median Cleft Face Syndrome 5.jpg
Boy with frontonasal dysplasia, showing hypertelorism

Midfacial malformations can be subdivided into two different groups. One group with hypertelorism, this includes FND. The other with hypotelorism (a decreased distance between the eyes), this includes holoprosencephaly (failure of development of the forebrain). [5] In addition, a craniofacial cleft can be classified using the Tessier classification. Each of the clefts is numbered from 0 to 14. The 15 different types of clefts are then subdivided into 4 groups, based on their anatomical position in the face: [6] midline clefts, paramedian clefts, orbital clefts and lateral clefts. FND is a midline cleft, classified as Tessier 0/14.

Tessier classification. Left: bony clefts, Right: Soft tissue clefts. Picture Tessier classification.jpg
Tessier classification. Left: bony clefts, Right: Soft tissue clefts.

Besides this, the additional anomalies seen in FND can be subdivided by region. None of these anomalies are specific for the syndrome of FND, but they do occur more often in patients with FND than in the population. The anomalies that may be present are:

The clefts of the face that are present in FND are vertical clefts. These can differ in severity. When they are less severe, they often present with hypertelorism and normal brain development. [8] Mental retardation is more likely when the hypertelorism is more severe or when extracephalic anomalies occur. [9]

Cause

Embryogenesis

Midline facial clefts are one of the symptoms in FND. These defects develop in the early stages of embryological development. This is around the 19th to 21st day of pregnancy. The cause of the defect is failure of the mesodermal migration. The mesoderm is one of the germ layers (a collection of cells that have the same embryological origin). As a result of this failure, a midline facial cleft is formed. [5]

Another symptom of FND is the V-shaped hairline. In the normal situation, hair growth surrounding the eyes is inhibited. However, in FND this suppression is prevented in the midline by the increased inter-ocular distance. This causes the so-called widow's peak (a V-shaped hairline) in FND patients. [9] [10]

Very early in embryogenesis, the face and neck develop. This development continues until adolescence. Organs develop out of primordia (tissue in its earliest recognizable stage of development). The developmental processes of the face and jaw structures originate from different primordia:

[11]

The head of a human embryo of about twenty-nine days old. Gray44.png
The head of a human embryo of about twenty-nine days old.

The formation of the frontonasal process is the result of a complex signaling system which begins with the synthesis of retinoic acid (a vitamin A metabolite). This is needed to set up the facial ectodermal zone. This zone makes signaling molecules that stimulate the cell proliferation of the frontonasal process. A midfacial defect will occur if this signaling pathway is disrupted. It is suggested that the absence of this pathway will lead to the formation of a gap, and that when the pathway is working too hard, excessive tissue will be formed. FND consists of various nasal malformations that result from excessive tissue in the frontonasal process, which results in hypertelorism and a broad nasal bridge.[ citation needed ]

Between the 4th and 8th week of pregnancy, the nasomedial and maxillary processes will fuse to form the upper lip and jaw. A failure of the fusion between the maxillary and nasomedial processes results in a cleft lip. A median cleft lip is the result of a failed fusion between the two nasomedial processes.

The palate is formed between the 6th and 10th week of pregnancy. The primordia of the palate are the lateral palatine processes and median palatine processes. A failure of the fusion between the median and lateral palatine processes results in a cleft palate. [11]

Genetics

There is still some discussion on whether FND is sporadic or genetic. The majority of FND cases are sporadic. Yet, some studies describe families with multiple members with FND. [3] [8] Gene mutations are likely to play an important role in the cause. Unfortunately, the genetic cause for most types of FND remains undetermined.

Frontorhiny

The cause of frontorhiny is a mutation in the ALX3 gene. ALX3 is essential for normal facial development. Different mutations can occur in the ALX3 gene, but they all lead to the same effect: severe or complete loss of protein functionality. [8] The ALX3 mutation never occurs in a person without frontorhiny. [12]

Acromelic frontonasal dysostosis

Acromelic frontonasal dysostosis is caused by a heterozygous mutation in the ZSWIM6 gene. It is thought that acromelic frontonasal dysostosis occurs due to an abnormality in the Sonic Hedgehog (SSH) signaling pathway. This pathway plays an important role in developing the midline central nervous system/craniofrontofacial region and the limbs. Hence, it is plausible that an error in the SSH pathway causes acromelic frontonasal dysostosis, because this syndrome not only shows abnormalities in the midfacial region, but also in the limbs and CNS. [10]

Diagnostics

The main diagnostic tools for evaluating FND are X-rays and CT-scans of the skull. These tools could display any possible intracranial pathology in FND. For example, CT can be used to reveal widening of nasal bones. Diagnostics are mainly used before reconstructive surgery, for proper planning and preparation. [8]

Prenatally, various features of FND (such as hypertelorism) can be recognized using ultrasound techniques. [9] However, only three cases of FND have been diagnosed based on a prenatal ultrasound. [13]

Other conditions may also show symptoms of FND. For example, there are other syndromes that also represent with hypertelorism. Furthermore, disorders like an intracranial cyst can affect the frontonasal region, which can lead to symptoms similar to FND. Therefore, other options should always be considered in the differential diagnosis. [9]

Types

Pai syndrome

The Pai Syndrome is a rare subtype of frontonasal dysplasia. It is a triad of developmental defects of the face, comprising midline cleft of the upper lip, nasal and facial skin polyps and central nervous system lipomas. When all the cases are compared, a difference in severity of the midline cleft of the upper lip can be seen. The mild form presents with just a gap between the upper teeth. The severe group presents with a complete cleft of the upper lip and alveolar ridge. [5]

Nervous system lipomas are rare congenital benign tumors of the central nervous system, mostly located in the medial line and especially in the corpus callosum. Generally, patients with these lipomas present with strokes. However, patients with the Pai syndrome don't. That is why it is suggested that isolated nervous system lipomas have a different embryological origin than the lipomas present in the Pai syndrome. The treatment of CNS lipomas mainly consists of observation and follow up. [5]

Skin lipomas occur relatively often in the normal population. However, facial and nasal lipomas are rare, especially in childhood. However, the Pai syndrome often present with facial and nasal polyps. [14] These skin lipomas are benign, and are therefore more a cosmetic problem than a functional problem.

The skin lipomas can develop on different parts of the face. The most common place is the nose. Other common places are the forehead, the conjunctivae and the frenulum linguae. The amount of skin lipomas is not related to the severity of the midline clefting. [5]

Patients with the Pai syndrome have a normal neuropsychological development.

Until today there is no known cause for the Pai syndrome. The large variety in phenotypes make the Pai syndrome difficult to diagnose. Thus the incidence of Pai syndrome seems to be underestimated. [14]

Acromelic frontonasal dysplasia (AFND)

Acromelic frontonasal dysplasia is a rare subtype of FND. It has an autosomal dominant inheritance. Acromelic frontonasal dysplasia is associated with central nervous system malformations and limb defects including a clubfoot, an underdeveloped shin-bone, and preaxial polydactyly of the feet. Preaxial polydactyly is a condition in which there are too many toes on the side of the big toe. [10] The phenotype of AFND is severe: a type Ia DeMyer and a Sedano type D. In contrast to the other subtypes of FND, AFND has a relatively high frequency of underlying malformations of the brain. [15]

Frontorhiny

Frontorhiny is another subtype of FND. It consists of multiple characteristics. Patient are characterized by: hypertelorism, a wide nasal bridge, a split nasal tip, a broad columella (strip of skin running from the tip of the nose to the upper lip), widely separated narrow nostrils, a long philtrum (vertical groove on the upper lip) and two-sided nasal swellings. [8]

Frontorhiny is one of the two subtypes of FND where a genetic mutation has been determined. The mutation has an autosomal recessive inheritance pattern. The syndrome is often seen in siblings and, most of the time, parents are carriers. See Genetics. [16]

Craniofrontonasal dysplasia

Craniofrontonasal dysplasia (CFND) is a rare type of FND with X linked inheritance. Multiple features are characteristic for CFND such as craniosynostosis of the coronal sutures (prematurely closed cranial sutures), dry frizzy curled hair, splitting of the nails and facial asymmetry.[ citation needed ]

There is a large variety in phenotype. Women present with a more severe phenotype than men. Females characteristically have FND, craniosynostosis and additional small malformations. Males are usually more mildly affected, presenting with only hypertelorism. The gene that causes CFND is called EFNB1 and is located on the X chromosome. A hypothesis for the more severe outcome in females is based on X-inactivation, which leads to mosaicism. As a result, patients have less functional cells, generating abnormal tissue boundaries, termed "cellular interference". This process almost never occurs in males, as they have less mutagenic material in their genes.[ clarification needed ] EFBN1 also has an important function in males. [16] As the syndrome has an X-linked inheritance pattern, there is no man-to-man inheritance. [3] [7]

Oculoauriculofrontonasal syndrome

OAFNS is a combination of FND and oculo-auriculo-vertebral spectrum (OAVS). [17]

The diagnosis of OAVS is based on the following facial characteristics: microtia (underdeveloped external ear), preauricular tags, facial asymmetry, mandibular hypoplasia and epibulbar lipodermoids (benign tumor of the eye which consists of adipose and fibrous tissue). There still remains discussion about the classification and the minimal amount of characteristics. When someone presents with FND and the characteristics of OAVS, the diagnosis OAFNS may be made. [17]

As the incidence of OAFNS is unknown, there are probably a lot of children with mild phenotypes that aren't being diagnosed as being OAFNS. [17]

The cause of OAFNS is unknown, but there are some theories about the genesis. Autosomal recessive inheritance is suggested because of a case with two affected siblings [18] and a case with consanguineous parents. [19] However, another study shows that it is more plausible that OAFNS is sporadic. [20] It is known that maternal diabetes plays a role in developing malformations of craniofacial structures and in OAVS. Therefore, it is suggested as a cause of OAFNS. Folate deficiency is also suggested as possible mechanism. [17]

Low-dose CT protocols should be considered in diagnosing children with OAFNS. [17]

Treatment

Because newborns can breathe only through their nose, the main goal of postnatal treatment is to establish a proper airway. [21] Primary surgical treatment of FND can already be performed at the age of 6 months, but most surgeons wait for the children to reach the age of 6 to 8 years. This decision is made because then the neurocranium and orbits have developed to 90% of their eventual form. Furthermore, the dental placement in the jaw has been finalized around this age. [21] [22]

Facial bipartition with median faciotomy

To correct the rather prominent hypertelorism, wide nasal root and midline cleft in FND, a facial bipartition can be performed. This surgery is preferred to periorbital box-osteotomy because deformities are corrected with a better aesthetic result. [22]

During the operation, the orbits are disconnected from the skull and the base of the skull. However, they remain attached to the upper jaw. Part of the forehead in the centre of the face is removed (median faciotomy) in the process. Then, the orbits are rotated internally, to correct the hypertelorism. Often, a new nasal bone will have to be interpositioned, using a bone transplant.

Complications of this procedure are: bleeding, meningitis, cerebrospinal fluid leakage and blindness. [23]

Rhinoplasty

Structural nasal deformities are corrected during or shortly after the facial bipartition surgery. In this procedure, bone grafts are used to reconstruct the nasal bridge. However, a second procedure is often needed after the development of the nose has been finalized (at the age of 14 years or even later).

Secondary rhinoplasty is based mainly on a nasal augmentation, since it has been proven better to add tissue to the nose than to remove tissue. This is caused by the minimal capacity of contraction of the nasal skin after surgery. [24]

In rhinoplasty, the use of autografts (tissue from the same person as the surgery is performed on) is preferred. However, this is often made impossible by the relative damage done by previous surgery. In those cases, bone tissue from the skull or the ribs is used. However, this may give rise to serious complications such as fractures, resorption of the bone, or a flattened nasofacial angle.To prevent these complications, an implant made out of alloplastic material could be considered. Implants take less surgery time, are limitlessly available and may have more favorable characteristics than autografts. However, possible risks are rejection, infection, migration of the implant, or unpredictable changes in the physical appearance in the long term.[ citation needed ]

At the age of skeletal maturity, orthognathic surgery may be needed because of the often hypoplastic maxilla. Skeletal maturity is at the age of six reached around the age of 13 to 16. Orthognathic surgery engages in diagnosing and treating disorders of the face and teeth- and jaw position. [21]

Related Research Articles

<span class="mw-page-title-main">Hypertelorism</span> Abnormally increased distance between two body parts, usually the eyes

Hypertelorism is an abnormally increased distance between two organs or bodily parts, usually referring to an increased distance between the orbits (eyes), or orbital hypertelorism. In this condition the distance between the inner eye corners as well as the distance between the pupils is greater than normal. Hypertelorism should not be confused with telecanthus, in which the distance between the inner eye corners is increased but the distances between the outer eye corners and the pupils remain unchanged.

<span class="mw-page-title-main">Popliteal pterygium syndrome</span> Medical condition

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.

<span class="mw-page-title-main">Nevoid basal-cell carcinoma syndrome</span> Medical condition

Nevoid basal-cell carcinoma syndrome (NBCCS) is an inherited medical condition involving defects within multiple body systems such as the skin, nervous system, eyes, endocrine system, and bones. People with this syndrome are particularly prone to developing a common and usually non-life-threatening form of non-melanoma skin cancer. About 10% of people with the condition do not develop basal-cell carcinomas (BCCs).

<span class="mw-page-title-main">Duane-radial ray syndrome</span> Medical condition

Duane-radial ray syndrome, also known as Okihiro Syndrome, is a rare autosomal dominant disorder that primarily affects the eyes and causes abnormalities of bones in the arms and hands. This disorder is considered to be a SALL4-related disorder due to the SALL4 gene mutations leading to these abnormalities. It is diagnosed by clinical findings on a physical exam as well as genetic testing and imaging. After being diagnosed, there are other evaluations that one may go through in order to determine the extent of the disease. There are various treatments for the symptoms of this disorder.

<span class="mw-page-title-main">Craniofrontonasal dysplasia</span> Medical condition

Craniofrontonasal dysplasia is a very rare X-linked malformation syndrome caused by mutations in the ephrin-B1 gene (EFNB1). Phenotypic expression varies greatly amongst affected individuals, where females are more commonly and generally more severely affected than males. Common physical malformations are: craniosynostosis of the coronal suture(s), orbital hypertelorism, bifid nasal tip, dry frizzy curled hair, longitudinal ridging and/or splitting of the nails, and facial asymmetry.

Aarskog–Scott syndrome (AAS) is a rare disease inherited as X-linked and characterized by short stature, facial abnormalities, skeletal and genital anomalies. This condition mainly affects males, although females may have mild features of the syndrome.

<span class="mw-page-title-main">3C syndrome</span> Medical condition

3C syndrome is a rare condition whose symptoms include heart defects, cerebellar hypoplasia, and cranial dysmorphism. It was first described in the medical literature in 1987 by Ritscher and Schinzel, for whom the disorder is sometimes named.

<span class="mw-page-title-main">Acrocallosal syndrome</span> Medical condition

Acrocallosal syndrome is an extremely rare autosomal recessive syndrome characterized by corpus callosum agenesis, polydactyly, multiple dysmorphic features, motor and intellectual disabilities, and other symptoms. The syndrome was first described by Albert Schinzel in 1979. Mutations in KIF7 are causative for ACLS, and mutations in GLI3 are associated with a similar syndrome.

<span class="mw-page-title-main">Michels syndrome</span> Medical condition

Michels syndrome is a syndrome characterised by intellectual disability, craniosynostosis, blepharophimosis, ptosis, epicanthus inversus, highly arched eyebrows, and hypertelorism. People with Michels syndrome vary in other symptoms such as asymmetry of the skull, eyelid, and anterior chamber anomalies, cleft lip and palate, umbilical anomalies, and growth and cognitive development.

<span class="mw-page-title-main">Fryns syndrome</span> Medical condition

Fryns syndrome is an autosomal recessive multiple congenital anomaly syndrome that is usually lethal in the neonatal period. Fryns (1987) reviewed the syndrome.

A facial cleft is an opening or gap in the face, or a malformation of a part of the face. Facial clefts is a collective term for all sorts of clefts. All structures like bone, soft tissue, skin etc. can be affected. Facial clefts are extremely rare congenital anomalies. There are many variations of a type of clefting and classifications are needed to describe and classify all types of clefting. Facial clefts hardly ever occur isolated; most of the time there is an overlap of adjacent facial clefts.

Malpuech facial clefting syndrome, also called Malpuech syndrome or Gypsy type facial clefting syndrome, is a rare congenital syndrome. It is characterized by facial clefting, a caudal appendage, growth deficiency, intellectual and developmental disability, and abnormalities of the renal system (kidneys) and the male genitalia. Abnormalities of the heart, and other skeletal malformations may also be present. The syndrome was initially described by Georges Malpuech and associates in 1983. It is thought to be genetically related to Juberg-Hayward syndrome. Malpuech syndrome has also been considered as part of a spectrum of congenital genetic disorders associated with similar facial, urogenital and skeletal anomalies. Termed "3MC syndrome", this proposed spectrum includes Malpuech, Michels and Mingarelli-Carnevale (OSA) syndromes. Mutations in the COLLEC11 and MASP1 genes are believed to be a cause of these syndromes. The incidence of Malpuech syndrome is unknown. The pattern of inheritance is autosomal recessive, which means a defective (mutated) gene associated with the syndrome is located on an autosome, and the syndrome occurs when two copies of this defective gene are inherited.

<span class="mw-page-title-main">Ectrodactyly</span> Medical condition

Ectrodactyly, split hand, or cleft hand involves the deficiency or absence of one or more central digits of the hand or foot and is also known as split hand/split foot malformation (SHFM). The hands and feet of people with ectrodactyly (ectrodactyls) are often described as "claw-like" and may include only the thumb and one finger with similar abnormalities of the feet.

Fryns-Aftimos syndrome is a rare chromosomal condition and is associated with pachygyria, severe mental retardation, epilepsy and characteristic facial features. This syndrome is a malformation syndrome, characterized by numerous facial dysmorphias not limited to hypertelorism, iris or retinal coloboma, cleft lip, and congenital heart defects. This syndrome has been seen in 30 unrelated people. Characterized by a de novo mutation located on chromosome 7p22, there is typically no family history prior to onset. The severity of the disorder can be determined by the size of the deletion on 7p22, enveloping the ACTB gene and surrounding genes, which is consistent with a contiguous gene deletion syndrome. Confirming a diagnosis of Fryns-Aftimos syndrome typically consists of serial single-gene testing or multigene panel of genes of interest or exome sequencing.

<span class="mw-page-title-main">Pascual-Castroviejo syndrome type 1</span> Medical condition

Pascual-Castroviejo syndrome type 1 is a rare autosomal recessive condition characterized by facial dysmorphism, cognitive impairment and skeletal anomalies.

<span class="mw-page-title-main">Bifid nose</span> Medical condition

A bifid nose is an uncommon congenital malformation which is characterized by the presence of a cleft between the two nostrils of the nose. It is the result of a disturbance during embryological nose development.

<span class="mw-page-title-main">Pai syndrome</span> Medical condition

Pai syndrome, also known as Median cleft of the upper lip-corpus callosum lipoma-midline facial cutaneous polyps syndrome, is a very rare genetic disorder which is characterized by nervous system, cutaneous, ocular, nasal and bucal anomalies with facial dysmorphisms.

The Crane–Heise syndrome is a very rare and lethal birth defect without a known cause. It was first described in a 1981 publication, and its main signs are facial malformations, lack of bone mineralization, and musculoskeletal anomalies.

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