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.

If a contracture is less than 30 degrees, it may not interfere with normal functioning. The common treatment is splinting and occupational therapy. Surgery is the last option for most cases as the result may not be satisfactory.

Due to a developmental arrest there is an abnormal alignment of the joint surfaces at either interphalangeal joint causing angulation in the plane of the palm. The finger may be slightly bent or have a very prominent bend.

The diagnosis of CdLS is primarily a clinical one, based on medical signs that are evident in a medical history, physical examination, and laboratory tests. Since 2006, testing for NIPBL and SMC1A has been available through the University of Chicago. This is best accomplished through a referral to a genetics specialist or clinic.

CdLS is thought to be underdiagnosed and frequently misdiagnosed.

Diagnosis is based on the distinctive cry and accompanying physical problems. These common symptoms are quite easily observed in infants. Affected children are typically diagnosed by a doctor or nurse at birth. Genetic counseling and genetic testing may be offered to families with individuals who have cri du chat syndrome. Prenatally the deletion of the cri du chat related region in the p arm of chromosome 5 can be detected from amniotic fluid or chorionic villi samples with BACs-on-Beads technology. G-banded karyotype of a carrier is also useful. Children may be treated by speech, physical and occupational therapists. Heart abnormalities often require surgical correction.

MRI will help with the diagnosis of structural abnormality of the brain. Genetic testing may also be pursued.

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.

The specific cause of camptodactyly remains unknown, but there are a few deficiencies that lead to the condition. A deficient lumbrical muscle controlling the flexion of the fingers, and abnormalities of the flexor and extensor tendons.

A number of congenital syndromes may also cause camptodactyly:

- Jacobsen syndrome

- Beals Syndrome

- Blau syndrome

- Freeman-Sheldon syndrome

- Cerebrohepatorenal syndrome

- Weaver syndrome

- Christian syndrome 1

- Gordon Syndrome

- Jacobs arthropathy-camptodactyly syndrome

- Lenz microphthalmia syndrome

- Marshall-Smith-Weaver syndrome

- Oculo-dento-digital syndrome

- Tel Hashomer camptodactyly syndrome

- Toriello-Carey syndrome

- Stuve-Wiedemann syndrome

- Loeys-Dietz syndrome

- Fryns syndrome

- Marfan's syndrome

- Carnio-carpo-tarsal dysthropy

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.

Diagnosing Jacobsen Syndrome can be difficult in some cases because it is a rare chromosomal disorder. There are a variety of tests that can be carried out like karyotype, cardiac echocardiogram, a renal sonogram, a platelet count, blood count, a brain imaging study. Genetic testing can be carried out for diagnosis. In which chromosomes are stained to give a barcode like appearance and studied under the microscope which reveals the broken and deleted genes. It can also be diagnosed early in the prenatal stage if there are any abnormalities seen in the ultrasound. A simple assessment of the symptoms can be done to diagnose the Syndrome. A thorough physical examination could be carried out to assess the symptoms.

Marshall–Smith syndrome is not to be confused with:

- Marshall syndrome (aka.Periodic fever, aphthous stomatitis, pharyngitis and adenitis (PFAPA syndrome, see also: Periodic fever syndrome)

- Sotos (like) syndrome

- Weaver-Smith syndrome (WSS)

Respiratory complications are often cause of death in early infancy.

The differential diagnosis includes Treacher Collins syndrome, Nager acrofacial dysostosis (preaxial cranial dysostosis). Other types of axial cranial dysostosis included the Kelly, Reynolds, Arens (Tel Aviv), Rodríguez (Madrid), Richieri-Costa and Patterson-Stevenson-Fontaine forms.

The Cornelia de Lange Syndrome (CdLS) Foundation is a nonprofit, family support organization based in Avon, Connecticut, that exists to ensure early and accurate diagnosis of CdLS, promote research into the causes and manifestations of the syndrome, and help people with a diagnosis of CdLS, and others with similar characteristics, make informed decisions throughout their lives.

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.

Brain MRI shows vermis atrophy or hypoplasic. Cerebral and cerebellar atrophy with white matter changes in some cases.

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.

Kosaki overgrowth syndrome (KOGS) is a rare (27 cases reported by 2017) syndrome caused by mutations in the PDGFRB gene.

Though only definitively diagnosable by genetic sequence testing, including a G band analysis, ATR-16 syndrome may be diagnosed from its constellation of symptoms. It must be distinguished from ATR-X syndrome, a very similar disease caused by a mutation on the X chromosome, and cases of alpha-thalassemia that co-occur with intellectual disabilities with no underlying genetic relationship.

Diagnosis of Harlequin syndrome is made when the individual has consistent signs and symptoms of the condition, therefore, it is made by clinical observation. In addition, a neurologist or primary care physician may require an MRI test to rule out similar disorders such as Horner's syndrome, Adie's syndrome, and Ross' syndrome. In an MRI, a radiologist may observe areas near brain or spinal cord for lesions, or any damage to the nerve endings. It is also important that the clinician rules out traumatic causes by performing autonomic function tests. Such tests includes the following: tilt table test, orthostatic blood pressure measurement, head-up test, valsalva maneuver, thermoregulatory sweat test, tendon reflex test, and electrocardiography (ECG). CT scan of the heart and lungs may also be performed to rule out a structural underlying lesion. The medical history of the individual should be carefully noted.

Miller syndrome is a genetic condition also known as the Genee–Wiedemann syndrome, Wildervanck–Smith syndrome, or postaxial acrofacial dystosis. The incidence of this condition is not known, but it is considered extremely rare. It is due to a mutation in the DHODH gene. Nothing is known of its pathogenesis.

Treatments for ATR-16 syndrome depend on the symptoms experienced by any individual. Alpha thalassemia is usually self-limiting, but in some cases may require a blood transfusion or chelating treatment.

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).

De Quervain syndrome is diagnosed clinically, based on history and physical examination, though diagnostic imaging such as x-ray may be used to rule out fracture, arthritis, or other causes, based on the patient's history and presentation. Finkelstein's test is a physical exam maneuver used to diagnose de Quervain syndrome. To perform the test, the examiner grasps the thumb and sharply deviates the hand toward the ulnar side. If sharp pain occurs along the distal radius (top of forearm, about an inch below the wrist), de Quervain's syndrome is likely. While a positive Finkelstein's test is often considered pathognomonic for de Quervain syndrome, the maneuver can also cause pain in those with osteoarthritis at the base of the thumb.

Differential diagnoses include:

1. Osteoarthritis of the first carpo-metacarpal joint

2. Intersection syndrome—pain will be more towards the middle of the back of the forearm and about 2–3 inches below the wrist

3. Wartenberg's syndrome

8p23.1 duplication syndrome is a rare genetic disorder caused by a duplication of a region from human chromosome 8. This duplication syndrome has an estimated prevalence of 1 in 64,000 births and is the reciprocal of the 8p23.1 deletion syndrome. The 8p23.1 duplication is associated with a variable phenotype including one or more of speech delay, developmental delay, mild dysmorphism, with prominent forehead and arched eyebrows, and congenital heart disease (CHD).