Pre-implantation genetic diagnosis (PGD or PIGD) is a technique used to identify genetically normal embryos and is useful for couples who have a family history of genetic disorders. This is an option for people choosing to procreate through IVF. PGD is considered difficult due to it being both time consuming and having success rates only comparable to routine IVF.

Blastomere biopsy is a technique in which blastomeres are removed from the zona pellucida. It is commonly used to detect aneuploidy. Genetic analysis is conducted once the procedure is complete. Additional studies are needed to assess the risk associated with the procedure.

Prenatal Diagnosis:

- Aymé, "et al." (1989) reported prenatal diagnosis of Fryns syndrome by sonography between 24 and 27 weeks.

- Manouvrier-Hanu et al. (1996) described the prenatal diagnosis of Fryns syndrome by ultrasonographic detection of diaphragmatic hernia and cystic hygroma. The diagnosis was confirmed after termination of the pregnancy. The fetus also had 2 erupted incisors; natal teeth had not been mentioned in other cases of Fryns syndrome.

Differential Diagnosis:

- McPherson et al. (1993) noted the phenotypic overlap between Fryns syndrome and the Pallister–Killian syndrome (601803), which is a dysmorphic syndrome with tissue-specific mosaicism of tetrasomy 12p.

- Veldman et al. (2002) discussed the differentiation between Fryns syndrome and Pallister–Killian syndrome, noting that differentiation is important to genetic counseling because Fryns syndrome is an autosomal recessive disorder and Pallister–Killian syndrome is usually a sporadic chromosomal aberration. However, discrimination may be difficult due to the phenotypic similarity. In fact, in some infants with 'coarse face,' acral hypoplasia, and internal anomalies, the initial diagnosis of Fryns syndrome had to be changed because mosaicism of isochromosome 12p was detected in fibroblast cultures or kidney tissue. Although congenital diaphragmatic hernia is a common finding in both syndromes, bilateral congenital diaphragmatic hernia had been reported only in patients with Fryns syndrome until the report of the patient with Pallister–Killian syndrome by Veldman et al. (2002).

- Slavotinek (2004) reviewed the phenotypes of 52 reported cases of Fryns syndrome and reevaluated the diagnostic guidelines. She concluded that congenital diaphragmatic hernia and distal limb hypoplasia are strongly suggestive of Fryns syndrome, with other diagnostically relevant findings including pulmonary hypoplasia, craniofacial dysmorphism, polyhydramnios, and orofacial clefting. Slavotinek (2004) stated that other distinctive anomalies not mentioned in previous guidelines include ventricular dilatation or hydrocephalus, agenesis of the corpus callosum, abnormalities of the aorta, dilatation of the ureters, proximal thumbs, and broad clavicles.

Suspicion of a chromosome abnormality is typically raised due to the presence of developmental delays or birth defects. Diagnosis of ring 18 is usually made via a blood sample. A routine chromosome analysis, or karyotype, is usually used to make the initial diagnosis, although it may also be made by microarray analysis. Increasingly, microarray analysis is also being used to clarify breakpoints. Prenatal diagnosis is possible via amniocentesis or chorionic villus sampling.

Suspicion of a chromosome abnormality is typically raised due to the presence of developmental delays or birth defects. Diagnosis of 18p- is usually made via a blood sample. A routine chromosome analysis, or karyotype, is usually used to make the initial diagnosis, although it may also be made by microarray analysis. Increasingly, microarray analysis is also being used to clarify breakpoints. Prenatal diagnosis is possible via amniocentesis of chorionic villus sampling.

Y chromosome microdeletion is currently diagnosed by extracting DNA from leukocytes in a man's blood sample, mixing it with some of the about 300 known genetic markers for sequence-tagged sites (STS) on the Y chromosome, and then using polymerase chain reaction amplification and gel electrophoresis in order to test whether the DNA sequence corresponding to the selected markers is present in the DNA.

Such procedures can test only the integrity of a tiny part of the overall 23 million base pair long Y chromosome, therefore the sensitivity of such tests depends on the choice and number of markers used. Present diagnostic techniques can only discover certain types of deletions and mutations on a chromosome and give therefore no complete picture of genetic causes of infertility. They can only demonstrate the presence of some defects, but not the absence of any possible genetic defect on the chromosome.

The gold standard test for genetic mutation, namely complete DNA sequencing of a patient's Y chromosome, is still far too expensive for use in epidemiologic research or even clinical diagnostics.

At present, treatment for ring 18 is symptomatic, meaning that the focus is on treating the signs and symptoms of the conditions as they arise. To ensure early diagnosis and treatment, it is suggested that people with ring 18 undergo routine screenings for thyroid, hearing, and vision problems.

Since Duane-radial ray syndrome is a genetic disorder, a genetic test would be performed. One test that can be used is the SALL4 sequence analysis that is used to detect if SALL4 is present. If there is no pathogenic variant observed, a deletion/duplication analysis can be ordered following the SALL4 sequence analysis. As an alternative, another genetic test called a multi-gene panel can be ordered to detect SALL4 and any other genes of interest. The methods used for this panel vary depending on the laboratory.

MRI imaging can be used to detect whether the abducens nerve is present.

1. Clinical Genetics and Genetic Testing

Genetic testing is necessary to confirm the diagnosis of PMS. A prototypical terminal deletion of 22q13 can be uncovered by karyotype analysis, but many terminal and interstitial deletions are too small to detect with this method. Chromosomal microarray should be ordered in children with suspected developmental delays or ASD. Most cases will be identified by microarray; however, small variations in genes might be missed. The falling cost for whole exome sequencing may replace DNA microarray technology for candidate gene evaluation. Biological parents should be tested with fluorescence "in situ" hybridization (FISH) to rule out balanced translocations or inversions. Balanced translocation in a parent increases the risk for recurrence and heritability within families (figure 3).

Clinical genetic evaluations and dysmorphology exams should be done to evaluate growth, pubertal development, dysmorphic features (table 1) and screen for organ defects (table 2)

2. Cognitive and Behavioral Assessment

All patients should undergo comprehensive developmental, cognitive and behavioral assessments by clinicians with experience in developmental disorders. Cognitive evaluation should be tailored for individuals with significant language and developmental delays. All patients should be referred for specialized speech/language, occupational and physical therapy evaluations.

3. Neurological Management

Individuals with PMS should be followed by a pediatric neurologist regularly to monitor motor development, coordination and gait, as well as conditions that might be associated with hypotonia. Head circumference should be performed routinely up until 36 months. Given the high rate of seizure disorders (up to 41% of patients) reported in the literature in patients with PMS and its overall negative impact on development, an overnight video EEG should be considered early to rule out seizure activity. In addition, a baseline structural brain MRI should be considered to rule out the presence of structural abnormalities.

4. Nephrology

All patients should have a baseline renal and bladder ultrasonography and a voiding cystourethrogram should be considered to rule out structural and functional abnormalities. Renal abnormalities are reported in up to 38% of patients with PMS. Vesicouretral reflux, hydronephrosis, renal agenesis, dysplasic kidney, polycystic kidney and recurrent urinary tract infections have all been reported in patients with PMS.

5. Cardiology

Congenital heart defects (CHD) are reported in samples of children with PMS with varying frequency (up to 25%)(29,36). The most common CHD include tricuspid valve regurgitation, atrial septal defects and patent ductus arteriousus. Cardiac evaluation, including echocardiography and electrocardiogram, should be considered.

6. Gastroenterology

Gastrointestinal symptoms are common in individuals with PMS. Gastroesophageal reflux, constipation, diarrhea and cyclic vomiting are frequently described.

Table 3: Clinical Assessment Recommendations in Phelan McDermid Syndrome.

At present, treatment for 18p- is symptomatic, meaning that the focus is on treating the signs and symptoms of the conditions as they arise. To ensure early diagnosis and treatment, it is suggested that people with 18p- undergo routine screenings for hearing and vision problems.

Microdeletions in the Y chromosome have been found at a much higher rate in infertile men than in fertile controls and the correlation found may still go up as improved genetic testing techniques for the Y chromosome are developed.

Much study has been focused upon the "azoospermia factor locus" (AZF), at Yq11. A specific partial deletion of AZFc called "gr/gr deletion" is significantly associated with male infertility among Caucasians in Europe and the Western Pacific region.

Additional genes associated with spermatogenesis in men and reduced fertility upon Y chromosome deletions include RBM, DAZ, SPGY, and TSPY.

Although LFS is usually suspected when intellectual disability and marfanoid habitus are observed together in a patient, the diagnosis of LFS can be confirmed by the presence of the p.N1007S missense mutation in the "MED12" gene.

In the differential diagnosis of LFS, another disorder that exhibits some features and symptoms of LFS and is also associated with a missense mutation of "MED12" is Opitz-Kaveggia syndrome (FGS). Common features shared by both LFS and FGS include X-linked intellectual disability, hyperactivity, macrocephaly, corpus callosum agenesis and hypotonia. Notable features of FGS that have not been reported with LFS include excessive talkativness, consistent strength in socialization skills, imperforate anus (occlusion of the anus) and ocular hypertelorism (extremely wide-set eyes).

Whereas LFS is associated with missense mutation p.N1007S, FGS is associated with missense mutation p.R961W. As both disorders originate from an identical type of mutation in the same gene, while exhibiting similar, yet distinct characteristics; LFS and FGS are considered to be allelic. In the context of "MED12", this suggests that the phenotype of each disorder is related to the way in which their respective mutations alter the "MED12" sequence and its function.

In France, Aymé, "et al." (1989) estimated the prevalence of Fryns syndrome to be 0.7 per 10,000 births based on the diagnosis of 6 cases in a series of 112,276 consecutive births (live births and perinatal deaths).

Diagnosis is usually based on clinical findings, although fetal chromosome testing will show trisomy 13. While many of the physical findings are similar to Edwards syndrome there are a few unique traits, such as polydactyly. However, unlike Edwards syndrome and Down syndrome, the quad screen does not provide a reliable means of screening for this disorder. This is due to the variability of the results seen in fetuses with Patau.

Identification of 45,X/46,XY karyotype has significant clinical implications due to known effects on growth, hormonal balance, gonadal development and histology. 45,X/46,XY is diagnosed by examining the chromosomes in a blood sample.

The age of diagnosis varies depending on manifestations of disease prompting reason for cytogenetic testing. Many patients are diagnosed prenatally due to fetal factors (increased nuchal fold, or abnormal levels of serum), maternal age or abnormal ultrasounds, while others will be diagnosed postnatal due to external genital malformation. It is not uncommon for patients to be diagnosed later in life due to short stature or delayed puberty, or a combination of both.

45,X/46,XY mosaicism can be detected prenatally through amniocentesis however, it was determined that the proportion of 45,X cells in the amniotic fluid cannot predict any phenotypic outcomes, often making prenatal genetic counselling difficult.

There is no consensus on what degree of angulation justifies a diagnosis, an incline between 15° and 30° is typical. A similar-sounding term, camptodactyly, is a fixed flexion deformity of a digit.

The duplication involved in PTLS is usually large enough to be detected through G-banding alone, though there is a high false negative rate. To ascertain the diagnosis when karyotyping results are unclear or negative, more sophisticated techniques such as subtelomeric fluorescent in-situ hybridization analysis and array comparative genomic hybridization (aCGH) may be used.

There is no known cure for this syndrome. Patients usually need ophthalmic surgery and may also need dental surgery

Genetic counseling and screening of the mother's relatives is recommended.

Due to the wide range of genetic disorders that are presently known, diagnosis of a genetic disorder is widely varied and dependent of the disorder. Most genetic disorders are diagnosed at birth or during early childhood, however some, such as Huntington's disease, can escape detection until the patient is well into adulthood.

The basic aspects of a genetic disorder rests on the inheritance of genetic material. With an in depth family history, it is possible to anticipate possible disorders in children which direct medical professionals to specific tests depending on the disorder and allow parents the chance to prepare for potential lifestyle changes, anticipate the possibility of stillbirth, or contemplate termination. Prenatal diagnosis can detect the presence of characteristic abnormalities in fetal development through ultrasound, or detect the presence of characteristic substances via invasive procedures which involve inserting probes or needles into the uterus such as in amniocentesis.

Initially, the clinical presentation of SDS may appear similar to cystic fibrosis. However, CF can be excluded with a normal chloride in sweat test but faecal elastase as a marker of pancreatic function will be reduced. The variation, intermittent nature, and potential for long-term improvement of some clinical features make this syndrome difficult to diagnose. SDS may present with either malabsorption, or hematological problems. Rarely, SDS may present with skeletal defects, including severe rib cage abnormalities that lead to difficulty in breathing. Diagnosis is generally based on evidence of exocrine pancreatic dysfunction and neutropenia. Skeletal abnormalities and short stature are characteristics that can be used to support the diagnosis. The gene responsible for the disease has been identified and genetic testing is now available. Though useful in diagnostics, a genetic test does not surmount the need for careful clinical assessment and monitoring of all patients.

More than 80% of children with Patau syndrome die within the first year of life. Children with the mosaic variation are usually affected to a lesser extent. In a retrospective Canadian study of 174 children with trisomy 13, median survival time was 12.5 days. One and ten year survival was 19.8% and 12.9% respectively.

Diagnosis of 48, XXXY is usually done by a standard karyotype. A karyotype is a chromosomal analysis in which a full set of chromosomes can be seen for an individual. The presence of the additional 2 X chromosomes on the karyotype are indicative of XXXY syndrome.

Another way to diagnosis 48, XXXY is by chromosomal microarray showing the presence of extra X chromosomes. Chromosomal microarray (CMA) is used to detect extra or missing chromosomal segments or whole chromosomes. CMA uses microchip-based testing to analyze many pieces of DNA. Males with 48, XXXY are diagnosed anywhere from before birth to adulthood as a result of the range in the severity of symptoms. The age range at diagnosis is likely due to the fact that XXXY is a rare syndrome, and does not cause as extreme phenotypes as other variants of Klinefelter syndrome (such as XXXXY).

Diagnostic testing could also be done via blood samples. Elevated levels of follicle stimulating hormone, luteinizing hormone, and low levels of testosterone can be indicative of this syndrome.

Turner syndrome may be diagnosed by amniocentesis or chorionic villus sampling during pregnancy.

Usually, fetuses with Turner syndrome can be identified by abnormal ultrasound findings ("i.e.", heart defect, kidney abnormality, cystic hygroma, ascites). In a study of 19 European registries, 67.2% of prenatally diagnosed cases of Turner Syndrome were detected by abnormalities on ultrasound. 69.1% of cases had one anomaly present, and 30.9% had two or more anomalies.

An increased risk of Turner syndrome may also be indicated by abnormal triple or quadruple maternal serum screen. The fetuses diagnosed through positive maternal serum screening are more often found to

have a mosaic karyotype than those diagnosed based on ultrasonographic abnormalities, and

conversely, those with mosaic karyotypes are less likely to have associated ultrasound abnormalities.