In terms of the diagnosis of Romano–Ward syndrome the following is done to ascertain the condition(the "Schwartz Score" helps in so doing):

- Exercise test

- ECG

- Family history

Prenatal screening is not typically done for FHM, however it may be performed if requested. As penetrance is high, individuals found to carry mutations should be expected to develop signs of FHM at some point in life.

"See the equivalent section in the main migraine article."

People with FHM are encouraged to avoid activities that may trigger their attacks. Minor head trauma is a common attack precipitant, so FHM sufferers should avoid contact sports. Acetazolamide or standard drugs are often used to treat attacks, though those leading to vasoconstriction should be avoided due to the risk of stroke.

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

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.

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.

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.

At least one clinical trial on readaptation of the vestibulo-ocular reflex undertaken by Dr Mingjia Dai from Mount Sinai Hospital in New York City has produced results for a significant percentage of patients who have participated in the program.

Dai has developed an intervention that provided improvement in symptoms for 70% of the patients in the clinical trial phase. The protocol involves a physical manipulation of the patient intended to readapt the vestibulo-ocular reflex. While the program is no longer in the research phase, Dai continues to accept patients. According to Dai, "success" is measured as a 50% reduction of symptoms.

Recent research reveals a very small percentage of MdDS cases may be related to optokinetic nystagmus (OKN).

MdDS is diagnosed several ways, one being by the symptoms: in particular, the "constant rocking, swaying feeling" and the abatement of this feeling when in motion again and as a matter of exclusion. There are no definitive tests that confirm MdDS, only tests that rule out other conditions. Tests include hearing and balance, and MdDS is generally diagnosed by either a neurologist or an ear nose & throat specialist.

Treatment for Romano–Ward syndrome can "deal with" the imbalance between the right and left sides of the sympathetic nervous system which may play a role in the cause of this syndrome. The imbalance can be temporarily abolished with a left stellate ganglion block, which shorten the QT interval. If this is successful, surgical ganglionectomy can be performed as a permanent treatment.Ventricular dysrhythmia may be managed by beta-adrenergic blockade (propranolol)

Laboratory testing reveals multiple mutations of HCS. Two genetic variants result in sporadic HCS symptoms, which are HCS-02 and HCS-03. These mutations produce symptoms that come and go, but have been present "de novo". HCS-03 was identified as the variant that is passed through afflicted family members and presents symptoms throughout the lifetime of the individual. All variants of HCS lead to the same premature termination of PEST sequences which compromise normal function of "NOTCH2". "NOTCH" has four different receptors, which have an affinity for similar ligands. They are classified as single-pass transmembrane receptors.

Weissenbacher-Zweymüller syndrome is diagnosed upon a thorough clinical evaluation, detailed patient history, identification of characteristic symptom and a variety of specialized tests which includes x-rays.

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.

The risk for untreated LQTS patients having events (syncopes or cardiac arrest) can be predicted from their genotype (LQT1-8), gender, and corrected QT interval.

- High risk (> 50%) - QTc > 500 ms, LQT1, LQT2, and LQT3 (males)

- Intermediate risk (30-50%) - QTc > 500 ms, LQT3 (females) or QTc < 500 ms, LQT2 (females) and LQT3

- Low risk (< 30%) - QTc < 500 ms, LQT1 and LQT2 (males)

A 1992 study reported that mortality for symptomatic, untreated patients was 20% within the first year and 50% within the first 10 years after the initial syncope.

Since about 2002, some patients with this disorder have been offered drug therapy with bisphosphonates (a class of osteoporosis drugs) to treat problems with bone resorption associated with the bone breakdown and skeletal malformations that characterize this disorder. Brand names include Actonel (risedronate/alendronate), made by Merck Pharmaceuticals. Other drugs include Pamidronate, made by Novartis and Strontium Ranelate, made by Eli Lilly. However, for more progressive cases, surgery and bone grafting are necessary.

There is no cure as of now. Treatment is directed towards the specific symptoms that are present in each individual. Individuals with hearing loss are able to get treated with hearing aids.

The diagnosis of LQTS is not easy since 2.5% of the healthy population has prolonged QT interval, and 10–15% of LQTS patients have a normal QT interval. A commonly used criterion to diagnose LQTS is the LQTS "diagnostic score", calculated by assigning different points to various criteria (listed below). With four or more points, the probability is high for LQTS; with one point or less, the probability is low. A score of two or three points indicates intermediate probability.

- QTc (Defined as QT interval / square root of RR interval)

- ≥ 480 ms - 3 points

- 460-470 ms - 2 points

- 450 ms and male gender - 1 point

- "Torsades de pointes" ventricular tachycardia - 2 points

- T wave alternans - 1 point

- Notched T wave in at least 3 leads - 1 point

- Low heart rate for age (children) - 0.5 points

- Syncope (one cannot receive points both for syncope and "torsades de pointes")

- With stress - 2 points

- Without stress - 1 point

- Congenital deafness - 0.5 points

- Family history (the same family member cannot be counted for LQTS and sudden death)

- Other family members with definite LQTS - 1 point

- Sudden death in immediate family members (before age 30) - 0.5 points

Medical diagnosis is required. Clinical tests can be performed, as well as molecular genetic testing. The available tests include:

Sequence analysis of the entire coding region

- Severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN) - Sanger Sequencing: Diagnosis, Mutation Confirmation, Pre-symptomatic, Risk Assessment, Screening

- Craniosynostosis: Diagnosis

- Invitae FGFR3-Related Disorders Test: Pre-symptomatic, Diagnosis, Therapeutic management

Mutation scanning of select exons

- Skeletal Dysplasia Panel: Diagnosis, Prognostic

Sequence analysis of select exons

- Severe Achondroplasia with Developmental Delay and Acanthosis Nigricans (SADDAN, FGFR3): Diagnosis, Mutation Confirmation, Risk Assessment

- Severe Achondroplasia, Developmental Delay, Acanthosis Nigricans: Diagnosis, Mutation Confirmation

Deletion/duplication analysis

- Invitae FGFR3-Related Disorders Test: Pre-symptomatic, Diagnosis, Therapeutic management

Life with SADDAN is manageable, although therapy, surgery, and lifelong doctor surveillance may be required.

A clinical diagnosis of SCS can be verified by testing the TWIST1 gene (only gene in which mutations are known to cause SCS) for mutations using DNA analysis, such as sequence analysis, deletion/duplication analysis, and cytogenetics/ FISH analysis. Sequence analysis of exon 1 (TWIST1 coding region) provides a good method for detecting the frequency of mutations in the TWIST1 gene. These mutations include nonsense, missense, splice site mutation, and intragenic deletions/insertions. Deletion/duplication analysis identifies mutations in the TWIST1 gene that are not readily detected by sequence analysis. Common methods include PCR, multiplex ligation-dependent probe amplification (MLPA), and chromosomal microarray (CMA). Cytogenetic/FISH analysis attaches fluorescently labels DNA markers to a denatured chromosome and is then examined under fluorescent lighting, which reveals mutations caused by translocations or inversions involving 7p21. Occasionally, individuals with SCS have a chromosome translocation, inversion, or ring chromosome 7 involving 7p21 resulting in atypical findings, such as, increased developmental delay. Individuals with SCS, typically have normal brain functioning and rarely have mental impairments. For this reason, if an individual has both SCS and mental retardation, then they should have their TWIST1 gene screened more carefully because this is not a normal trait of SCS. Cytogenetic testing and direct gene testing can also be used to study gene/chromosome defects. Cytogenetic testing is the study of chromosomes to detect gains or losses of chromosomes or chromosome segments using fluorescent in situ hybridization (FISH) and/or comparative genomic hybridization (CGH). Direct gene testing uses blood, hair, skin, amniotic fluid, or other tissues in order to find genetic disorders. Direct gene testing can determine whether an individual has SCS by testing the individual's blood for mutations in the TWIST1 gene.

Revesz syndrome has so far been observed only in children. There is not much information about the disease because of its low frequency in general population and under reporting of cases.

Diagnosis may be suspected on the basis of the clinical and radiologic findings, and can supported by molecular analysis of the SHOX, SHOXY and PAR1 genes.

May also be suspected by ultrasound during the second trimester of gestation.

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.

Up until recently, experts frequently disagreed on whether a patient had SCS, Crouzon syndrome, isolated craniosynostosis, or some other disease because the symptoms are so closely related, they literally had no way of differentiating between all of them. However, we now have direct gene testing, which allows for a more definitive diagnosis because it allows them to be differentiated from each other based on which gene is mutated in each condition. The following is a list of conditions commonly confused/misdiagnosed for SCS, some of their symptoms, and which mutated gene each contains:

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.

Diagnosis is based on physical examination including radiographs of the hands and feet and imaging studies of the kidneys, bladder, and female reproductive tract. HOXA13 is the only gene known to be associated with HFGS. Approximately 60% of mutations are polyalanine expansions. Molecular genetic testing is clinically available.