Laboratory Studies
See the list below:
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Molecular analysis of Apert syndrome
The molecular mechanism is exquisitely specific with a narrow mutational spectrum.
More than 98% of cases are caused by specific missense substitution mutations involving adjacent amino acids (Ser252Trp, Ser252Phe, or Pro253Arg) in exon 7 of FGFR2.
The remaining cases are due to Alu-element insertion mutations in or near exon 9.
Imaging Studies
Imaging studies can reveal various aspects of Apert syndrome. (See the images below.)
A 17-month-old boy with Apert syndrome. Three-dimensional (3-D) CT imaging of the head showed craniosynostosis of the coronal suture and a hypoplastic midface.
Axial facial CT scans in the same patient as in the previous image showed bilateral shallowed orbits with proptosis and mild hypertelorism. Crowding of the teeth was present.
Radiograph of bilateral hands in the same patient as in the previous images, at age 18 months, showed bilateral syndactyly involving the second through fifth digits, with absent distal phalanges. Bilateral shortened hypoplastic middle phalanges are present, with bony fusion at the third and fourth middle phalanges, along with deformities of the proximal phalanges and shortened metacarpals.
Radiograph of bilateral feet in the same patient as in the previous images, at age 7 years, showed syndactyly with diffuse deformities and multiple midfoot and hindfoot tarsal coalitions.
Three-dimensional facial CT scans in the same child as in the previous images, at age 9 years, showed hypoplastic midfacial bones.
See the list below:
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Skull radiography
Skull radiography can be performed to evaluate for craniostenosis, which usually involves coronal sutures and maxillary hypoplasia.
Abnormalities include sclerosis of suture line, bony bridging and beaking along the suture line, an indistinct suture line, turribrachycephaly, shallow orbits, and hypoplastic maxillae.
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Spinal radiography
Spinal fusions, most commonly at the levels of C3-4 and C5-6, appear to be progressive and occur at the site of subtle congenital anomalies. They may not be apparent as congenital features.
Small-sized vertebral body and reduced intervertebral disc space are indicators of subsequent bony fusion.
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Limb radiography: Radiographs of the limbs depict multiple epiphyseal dysplasia, short humeri, and glenoid dysplasia.
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Hand radiography
Radiography of the hands can be performed to evaluate for cutaneous and osseous syndactyly.
The characteristic finding is complete syndactyly involving the second and fifth digits (mitten hands).
Multiple progressive synostosis involves distal phalanges, proximal fourth and fifth metacarpals, capitate, and hamate.
Symphalangism of interphalangeal joints is progressive.
Radiography of the distal phalanx reveals shortened and radial deviation.
Radiography of the proximal phalanx of the thumbs reveals delta-shaped deformity.
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Foot radiography
Radiography of the feet can be performed to evaluate for cutaneous and osseous syndactyly. The characteristic finding is complete syndactyly involving the second and fifth digits (sock feet).
Fusion of tarsal bones, metatarsophalangeal and interphalangeal joints, and adjacent metatarsals
Delta-shaped proximal phalanx of the first toes
Occasional partial or complete duplication of the proximal phalanx of the great toes and first metatarsals
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CT scanning
CT scanning with comparative three-dimensional reconstruction analysis of the calvaria and cranial bases has become the most useful radiologic examination in identifying skull shape and the presence or absence of involved sutures.
CT scanning can precisely reveal the pathologic anatomy and permit specific operative planning.
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MRI
MRI reveals the anatomy of the soft-tissue structures and associated brain abnormalities (ie, nonprogressive ventriculomegaly; hydrocephalus; complete or partial absence of the septum pellucidum; absence of septal leaflets; and thinning, deficiency, or agenesis of the corpus callosum). [2, 3]
MRI can also reveal spatial arrangement of the bones.
Other Tests
See the list below:
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Psychometric evaluation
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Hearing assessment
Genetic counseling [25]
A negligible risk for Apert syndrome is noted in siblings of affected individuals when parents are not affected, except in the case of germinal mosaicism; in this case, the risk in future siblings depends on the proportion of germ cells that bear the mutant allele. [26]
A 50% risk for Apert syndrome is present in the siblings of an affected individual if a parent is also affected.
A 50% risk for Apert syndrome is observed in offspring of an affected individual.
Advanced paternal age effect in new mutations has been shown clinically and demonstrated conclusively at the molecular level.
Prenatal diagnosis [25]
Despite the striking physical features seen in newborns with Apert syndrome, de novo cases are often not diagnosed prenatally, or are only identified in the third-trimester. [2, 3]
Prenatal ultrasonographic diagnosis can be made based on findings of acrocephaly, mittenlike hands, and proximally placed and radially deviated thumbs. [27] CNS malformations such as mild ventriculomegaly and agenesis of corpus callosum may be visible in some fetuses with Apert syndrome before the pathognomonic skeletal changes are revealed. The abnormal cranial shape and orbital hypertelorism may be absent or very subtle in the second trimester of pregnancy, becoming obvious only in the third trimester. However, Apert syndrome can be accurately suspected in the second trimester by careful ultrasonographic examination of the fetus, including the extremities and skull shape using 3-dimensional ultrasonography.
Use of three-dimensional ultrasonography to demonstrate the fetal abnormalities (eg, premature closure of the coronal suture; a wide metopic suture; abnormalities of the hands, feet, and face) is particularly useful in parental counseling. [28]
If the molecular defect has been identified in the affected parent, prenatal molecular diagnosis can be achieved by direct DNA testing on fetal DNA obtained from amniocentesis or chronic villus sampling (CVS). In general, linkage analysis can be considered if a mutation has not been detected in the affected parent (although >98% of patients with Apert syndrome tested so far have FGFR2 mutations) and at least 2 affected relatives are available.
The abnormal sonographic findings with a high suspicion of Apert syndrome should be confirmed by detection of a mutation in the FGFR2 gene. Two mutations, S252W C→G and P253R C→G are found in 98% of patients. [29]
Fetoscopy to visualize fetal anomalies comparable to Apert syndrome in a pregnancy at risk is an invasive procedure and is not currently used.
Noninvasive prenatal diagnosis of Apert syndrome using polymerase chain reaction (PCR) and restriction enzyme digestion of cffDNA in maternal plasma has been reported. [30] Au et al have developed a real-time qPCR assay using molecular beacon probes to detect the S252W mutation in the FGFR2 gene, in fetal DNA extracted from plasma of pregnant women at risk for Apert syndrome. [31]
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An infant with Apert syndrome is shown. Note the characteristic ocular hypertelorism, down-slanting palpebral fissures, proptotic eyes, horizontal groove above the supraorbital ridge, break of the eyebrows' continuity, depressed nasal bridge, and short, wide nose with bulbous tip.
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Note the mitten appearance of the hands with syndactyly involving the second, third, fourth, and fifth fingers. This patient also has characteristic concave palms, hitchhiker posture (radial deviation) of the short broad thumbs, and contiguous nail beds (synonychia).
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Note the socklike appearance of the feet with syndactyly involving the second, third, fourth, and fifth toes. The patient also has contiguous nail beds (synonychia).
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In this profile photo, turribrachycephaly (high prominent forehead), proptosis, a depressed nasal bridge, a short nose, and low-set ears are prominent.
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This radiograph demonstrates turribrachycephaly, shallow orbits, ocular hypertelorism, and a hypoplastic maxilla.
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Note the osseous syndactyly involving the second, third, fourth, and fifth fingers; multiple synostosis involving the distal phalanges and proximal fourth and fifth metacarpals; symphalangism of the interphalangeal joints; shortening and radial deviation of the distal phalanx; and the delta-shaped deformity of proximal phalanx of the thumbs.
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Note the osseous syndactyly, fusion of the interphalangeal joints, synostosis involving the proximal first and second metatarsals, and the partially duplicated and delta-shaped proximal phalanx of the great toes.
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A 9-month-old girl was seen because of syndactyly of the hands and feet as well as associated with craniofacial anomalies. The family and pregnancy histories were noncontributory. The child had broad thumbs with 2-5 digits with cutaneous syndactyly (only the right hand is shown here). The feet were characterized by brachydactyly and syndactyly of 2-5 toes. Genomic DNA analysis showed a heterozygous C-to-G mutation at nucleotide 755 of the fibroblast growth factor receptor 2 (FGFR2) gene (c.755C>G) that changes a codon for serine (TCG) to that for tryptophan (TGG) at amino acid position 252 (p.Ser252Trp). This mutation is diagnostic for Apert syndrome.
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The right hand radiograph for the same patient in the previous image, at age 15 months (left image), showed soft-tissue fusion between the second through fourth digits as well as fusion of the proximal soft tissues between the fourth and fifth digits. Hypoplastic, deformed phalanges were present with fusion of the proximal and middle phalanges of the second through fourth digits. Bony fusion was also seen at the bases of the fourth and fifth metacarpals along with fusion of the capitate and hamate. The thumb pointed laterally with a sharp angulation at the first metacarpophalangeal joint. A right hand radiograph from the child at age 1 month (right image) is provided for comparison. Similar abnormalities were also seen in the left hand (not shown).
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Radiographs of both feet in the same child as in the previous images, at age 1 month, showed foreshortening of the bilateral second metatarsals, the right third proximal phalanx and left fourth phalanx, and the distal phalanges of the left second, third, fourth, and fifth digits. Both great toes are bulbous and foreshortened, with deformed phalanges and partially duplicated metatarsals. Soft-tissue fusion was present in the second through fifth digits of both feet.
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Magnetic resonance images of the brain obtained at in the same patient as in the previous images, at age 16 months, showed hypoplasia of the parieto-occipital white matter, with undulating bilateral lateral ventricle occipital horns (arrow; left image). Shallow orbits can be appreciated bilaterally with ocular hypertelorism (right image).
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A 17-month-old boy with Apert syndrome. Three-dimensional (3-D) CT imaging of the head showed craniosynostosis of the coronal suture and a hypoplastic midface.
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Axial facial CT scans in the same patient as in the previous image showed bilateral shallowed orbits with proptosis and mild hypertelorism. Crowding of the teeth was present.
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Radiograph of bilateral hands in the same patient as in the previous images, at age 18 months, showed bilateral syndactyly involving the second through fifth digits, with absent distal phalanges. Bilateral shortened hypoplastic middle phalanges are present, with bony fusion at the third and fourth middle phalanges, along with deformities of the proximal phalanges and shortened metacarpals.
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Radiograph of bilateral feet in the same patient as in the previous images, at age 7 years, showed syndactyly with diffuse deformities and multiple midfoot and hindfoot tarsal coalitions.
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Three-dimensional facial CT scans in the same child as in the previous images, at age 9 years, showed hypoplastic midfacial bones.
