FGFR2

Jackson-Weiss Syndrome

Clinical Characteristics
Ocular Features: 

The facial malformation such as the flattened midface with maxillary hypoplasia leads to shallow orbits with the result that the eyes appear proptotic.  Some but not all individuals have strabismus, usually exotropia.  Optic atrophy has not been reported. 

Systemic Features: 

Infants usually present at birth with skull deformities resembling some variant of acrocephalosyndactyly.  Some or all of the skull sutures may be fused.  In some individuals craniectomy is necessary while others have normal brain development.  Few patients have evidence of abnormal neurological development and psychometric testing reveals IQ's in the normal range.  The midface is flattened with sometimes severe maxillary hypoplasia.  No hand deformities are present. 

There may be cutaneous syndactyly of the second and third toes.  Variable tarsal fusion is often present. The great toe may be abnormally broad and deviated medially.  The first metatarsals and proximal phalanges of the great toes are generally broad.

The phenotype is highly variable and even among individuals in genetically more homogeneous populations such as the Old Order Amish the range of facial, skull, and digital anomalies include features found among all of the craniosynostosis syndromes except for Apert syndrome.

Genetics

Heterozygous mutations in the FGFR2 gene (10q26.13) are likely responsible for this autosomal dominant condition. 

Other forms of craniosynostosis in which mutations in FGFR2 have been found are: Beare-Stevenson Syndrome (123790), Crouzon Syndrome (123500), Pfeiffer Syndrome (101600), Apert Syndrome (101200), and Saethre-Chotzen Syndrome (101400).

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

There is no treatment beyond surgical correction of selected malformations. The risk of exposure keratitis requires constant vigilance and appropriate corneal lubrication.

References
Article Title: 

Beare-Stevenson Syndrome

Clinical Characteristics
Ocular Features: 

The midface hypoplasia and shallow orbits result in the appearance of prominent eyes.  Ptosis and hypertelorism have been reported while the palpebral fissures are downslanting. One patient has been reported to have optic atrophy.  Another patient was described with cloudy corneas, irregular irides and nonreactive pupils.

Systemic Features: 

Pregnancies may be complicated by polyhydramnios.  Infants are born with craniosynostosis with a cloverleaf pattern usually.  The skull is often shortened in the anteroposterior axis with flattening of the occipital region.  The skin is deeply furrowed with the cutis gyrata patterns most prominent in the posterior scalp but also present on the palms, soles, pinnae, and elsewhere.  Acanthosis nigricans is often present.

There is midface hypoplasia and nearly all individuals have intellectual disability.

The external ear canals can be atretic, the nares are often anteverted, and the mouth may be small.  An excess number of neonatal teeth and hypoplastic nails have been noted.  Hydrocephalus is common.  The umbilical stump is often unusually prominent.  Anogenital anomalies such as an anteriorly placed anus, cryptorchidism, and bifid scrotum may be present.  Pyloric stenosis is sometimes present.

Upper airway obstruction with respiratory distress may necessitate a tracheotomy. A cartilaginous tracheal sleeve replacing the normal C rings of cartilage has been found in several infants. These can be difficult to detect and their presence may have been responsible for breathing restrictions that has led to the demise of some children before two years of age.

Genetics

Reported cases have occurred sporadically.  Increased paternal age has been suggested as a factor in the occurrence of heterozygous mutations in the FGFR2 gene (10q26.13) which have been identified in some individuals.

Other forms of craniosynostosis in which mutations in FGFR2 have been found are: Crouzon Syndrome (123500), Pfeiffer Syndrome (101600), Apert Syndrome (101200), Jackson-Weiss Syndrome (123150), and Saethre-Chotzen Syndrome (101400).

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

There is no general treatment for this syndrome.  Several infants have had tracheotomies and CNS shunts.

References
Article Title: 

Beare-Stevenson cutis gyrata syndrome

Hall BD, Cadle RG, Golabi M, Morris CA, Cohen MM Jr. Beare-Stevenson cutis gyrata syndrome. Am J Med Genet. 1992 Sep 1;44(1):82-9. PubMed PMID: 1519658.

PubMed ID: 
1519658

Pfeiffer Syndrome

Clinical Characteristics
Ocular Features: 

Patients may have extreme proptosis (95%) secondary to shallow orbits and exposure keratitis (41%) is a risk.  Hypertelorism, strabismus, and antimongoloid lid slants are common.  More rare signs include anterior chamber anomalies and optic nerve hypoplasia.

Systemic Features: 

Pfeiffer syndrome has been divided into 3 types, of which cases with types 2 and 3 often die young.  Type 1 has the more typical features with midface hypoplasia, broad thumbs and toes, craniosynostosis, and often some degree of syndactyly.  Adult patients with type 1 may be only mildly affected with some degree of midface hypoplasia and minor broadening of the first digits.  Hearing loss secondary to bony defects is relatively common.  Cleft palate is uncommon.  Airway malformations especially in the trachea can cause respiratory problems.

Genetics

This is a genetically heterogeneous disorder resulting from mutations in at least 2 genes, FGFR1 (8p11.2-p11.1) and FGFR2 (10q26).  The less common cases with the latter mutation are allelic to Apert (101200), Crouzon (123500), and Jackson-Weiss (123150) syndromes.  Inheritance is autosomal dominant but some cases are only mildly affected.  New mutations exhibit a paternal age effect.

Other forms of craniosynostosis in which mutations in FGFR2 have been found are: Beare-Stevenson Syndrome (123790), and Saethre-Chotzen Syndrome (101400).

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Exposure keratitis requires the usual treatment.  Fronto-orbital advancement surgery for the midface underdevelopment is generally helpful for the complications of proptosis.  Airway obstruction may require tracheostomy or surgical correction of the air passages.

References
Article Title: 

FGFR2 mutations in Pfeiffer syndrome

Lajeunie E, Ma HW, Bonaventure J, Munnich A, Le Merrer M, Renier D. FGFR2 mutations in Pfeiffer syndrome. Nat Genet. 1995 Feb;9(2):108.

PubMed ID: 
7719333

Crouzon Syndrome

Clinical Characteristics
Ocular Features: 

The primary ocular features result from pattern-specific, premature synostoses of cranial sutures.  The orbits are often shallow resulting in proptosis, sometimes to such an extent that exposure keratitis or even spontaneous subluxation of the globe results.  This is exacerbated by the midface hypoplasia that is often present.  As many as 22% of patients have optic atrophy, most likely secondary to chronic papilledema from elevated intracranial pressure.  Strabismus is common, often with a V-pattern exotropia.  Overaction of the inferior obliques and underaction of the superior obliques have been described.

Systemic Features: 

The coronal sutures are the most commonly affected by the premature synostosis and hence the skull is often brachycephalic and the forehead is prominent.  Increased intracranial pressure is a risk.  The nose is parrot-beaked and the upper lip is short.  Maxillary hypoplasia from the midface underdevelopment can cause crowding and displacement of the upper teeth.

Genetics

This type of craniosynostosis is caused by mutations in the fibroblast growth factor receptor-2 gene, FGFR2, located at 10q26.  It is generally considered an autosomal dominant disorder based on familial cases but most occur sporadically.  A paternal age effect on mutations has been found. 

The same gene is mutant in other craniosynostosis disorders sometimes clinically separated such as Pfeiffer Syndrome (101600), Jackson-Weiss syndrome (123150), Beare-Stevenson Syndrome (123790), Apert Syndrome (101200), and Saethre-Chotzen Syndrome (101400).  However, this entire group has many overlapping features making classification on clinical grounds alone difficult.  Only Apert syndrome (101200) is caused by a unique mutation whereas other syndromes seem to owe their existence to multiple mutations.

 

 

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Exposure keratitis must be treated.  Cranial surgery has been necessary for some patients to relieve the papilledema but the post operative outcome can be complicated by hydrocephalus.

References
Article Title: 

Apert Syndrome

Clinical Characteristics
Ocular Features: 

In 10% of patients, keratitis and corneal scarring occur from the sometimes marked proptosis and corneal exposure.  Optic atrophy is present in over 20% of patients.  Strabismus, primarily exotropia, is found in more than 70% and various extraocular muscle anomalies may be detectable.  Usually the exotropia has a V-pattern with overaction of the inferior oblique muscles while the superior oblique is weak.  Amblyopia occurs in nearly 20%.  The lid fissures often slant downward and the eyebrows may be interrupted.

Systemic Features: 

This brachysphenocephalic type of acrocephaly is associated with syndactyly in the hands and feet.  Pre- and postaxial polydactyly may be present.  There is considerable variation in expression with some patients so mildly affected that they appear virtually normal, whereas others have extreme degrees of brachycephaly with high foreheads, midface hypoplasia, and proptosis secondary to shallow orbits.  Imaging often reveals one or more CNS anomalies such as defects of the corpus callosum, partial absence of the septum pellucidum, ventriculomegaly, and sometimes hydrocephalus.  A small but significant proportion of patients have some developmental delay and cognitive impairment.  Over 39% of patients have a normal IQ.

Genetics

This type of craniosynostosis is caused by mutations in the fibroblast growth factor receptor-2 gene, FGFR2, located at 10q26.13.  It is generally considered an autosomal dominant disorder based on familial cases but most occur sporadically.  A paternal age effect on mutations has been found.  The same gene is mutant in allelic disorders sometimes clinically separated and labeled Crouzon (123500) and Pfeiffer (some cases) (101600) syndromes.  Jackson-Weiss syndrome (123150) maps to the same locus.  However, this entire group has many overlapping features making classification on clinical grounds alone difficult.  Only Apert syndrome is caused by mutations in a single gene whereas other syndromes seem to result from mutations in multiple genes.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No specific treatment is available for this disorder but exposure keratitis may require surveillance and therapy.

References
Article Title: 
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