Arts syndrome should be included in the differential diagnosis of infantile hypotonia and weakness aggravated by recurrent infection with a family history of X-linked inheritance. Sequence analysis of PRPS1, the only gene associated with Arts syndrome, has detected mutations in both kindreds reported to date. Arts syndrome patients were also found to have reduced levels of hypoxanthine levels in urine and uric acid levels in the serum. In vitro, PRS-1 activity was reduced in erythrocytes and fibroblasts.

While the clinical picture may point towards the diagnosis of the Roussy–Lévy syndrome, the condition can only be confirmed with absolute certainty by carrying out genetic testing in order to identify the underlying mutations.

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.

The degeneration of white matter, which shows the degeneration of myelin, can be seen in a basic MRI and used to diagnose leukodystrophies of all types. T-1 and T-2 weighted FLAIR images are the most useful. FLAIR stands for fluid-attenuated inversion recovery. Electrophysiological and other kinds of laboratory testing can also be done. In particular, nerve conduction velocity is looked at to distinguish between leukodystrophy and other demyelinating diseases, as well as to distinguish between individual leukodystrophies. For example, individuals with X-ALD have normal conduction velocities, while those with Krabbe disease or metachromatic leukodystrophy have abnormalities in their conduction velocities. Next generation multigene sequencing panels for undifferentiated leukodystrophy can now be offered for rapid molecular diagnosis after appropriate genetic counselling.

Though it is only definitively diagnosed by a genetic test, autosomal dominant porencephaly type I can be suspected if the disease is known to run in the family or if someone shows symptoms. CT scanning or MRI may be useful in indicating a diagnosis. COL4A1 may be mutated in other diseases that need to be distinguished, including brain small vessel disease with hemorrhage and HANAC syndrome. CADASIL syndrome is caused by a mutation in a different gene, but may cause similar symptoms. Sporadic porencephaly is another disorder that can appear similar.

Diagnosis of otodental syndrome was established using clinical, histopathological and audiometric methodologies. In normal individuals, by the age of 2-3, radiograph images should depict any signs of premolar development. A formal diagnosis of no premolar growth can be done by age 6 in order to check for signs of otodental syndrome. Sensorineural hearing loss can be another measure for proper diagnosis as well as checking for ocular coloboma. The latter is usually noticed at an around birth.

Molecular genetic testing can aid in the diagnosis of the affected individual, which would determine if there are any abnormalities in the FGF3 gene (11q13) or the FADD gene (11q13.3). Additional tests that can help diagnose otodental syndrome are ear infection tests, hearing tests, oral examination, and eye examinations to check for the specific phenotypic associations. Due to the rarity of otodental syndrome, most symptoms are looked at on an individual basis unless multiple symptoms are all apparent at once.

There is potential for differential diagnosis due to similarities in symptoms. Other diseases that share common symptoms are chondroectodermal dysplasia, achondrodysplasia, and osteopetrosis

CMT can be diagnosed through symptoms, through measurement of the speed of nerve impulses (nerve conduction studies), through biopsy of the nerve, and through DNA testing. DNA testing can give a definitive diagnosis, but not all the genetic markers for CMT are known. CMT is first noticed when someone develops lower leg weakness, such as foot drop; or foot deformities, including hammertoes and high arches. But signs alone do not lead to diagnosis. Patients must be referred to a physician specialising in neurology or rehabilitation medicine. To see signs of muscle weakness, the neurologist asks patients to walk on their heels or to move part of their leg against an opposing force. To identify sensory loss, the neurologist tests for deep tendon reflexes, such as the knee jerk, which are reduced or absent in CMT. The doctor also asks about family history, because CMT is hereditary. The lack of family history does not rule out CMT, but helps rule out other causes of neuropathy, such as diabetes or exposure to certain chemicals or drugs.

In 2010, CMT was one of the first diseases where the genetic cause of a particular patient's disease was precisely determined by sequencing the whole genome of an affected individual. This was done by the scientists employed by the Charcot Marie Tooth Association (CMTA) Two mutations were identified in a gene, SH3TC2, known to cause CMT. Researchers then compared the affected patient's genome to the genomes of the patient's mother, father, and seven siblings with and without the disease. The mother and father each had one normal and one mutant copy of this gene, and had mild or no symptoms. The offspring that inherited two mutant genes presented fully with the disease.

There are very few ways to test a patient for HGF. Currently, the most common way to diagnose a patient is by means of a physical evaluation. The physician can make a physical evaluation of the patient and send them to a dentist or better yet a specialist like a periodontist to evaluate signs of gingival overgrowth, quality of gingiva, inflammation, mechanical difficulties of the mouth, tooth conditions, and any sort of discomfort.

Aside from obvious physical symptoms seen in a physical evaluation, molecular tests can be run to check if there is a mutation in the SOS1 gene to confirm the diagnosis. If there is indeed a mutation in this gene coupled with the typical physical symptoms, then it is quite probable that a patient suffers from this disease. Also, looking at family history is also becoming more prominent in aiding to diagnose the patient. Otherwise, researchers are working to find new and better ways to test for the presence of HGF.

Currently, purine replacement via S-adenosylmethionine (SAM) supplementation in people with Arts syndrome appears to improve their condition. This suggests that SAM supplementation can alleviate symptoms of PRPS1 deficient patients by replacing purine nucleotides and open new avenues of therapeutic intervention. Other non-clinical treatment options include educational programs tailored to their individual needs. Sensorineural hearing loss has been treated with cochlear implantation with good results. Ataxia and visual impairment from optic atrophy are treated in a routine manner. Routine immunizations against common childhood infections and annual influenza immunization can also help prevent any secondary infections from occurring.

Regular neuropsychological, audiologic, and ophthalmologic examinations are also recommended.

Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible if the disease-causing mutation in the family is known.

MJD can be diagnosed by recognizing the symptoms of the disease and by taking a family history. Physicians ask patients questions about the kind of symptoms relatives with the disease had, the progression and harshness of symptoms, and the ages of onset in family members.

Presymptomatic diagnosis of MJD can be made with a genetic test. The direct detection of the genetic mutation responsible for MJD has been available since 1995. Genetic testing looks at the number of CAG repeats within the coding region of the MJD/ATXN3 gene on chromosome 14. The test will show positive for MJD if this region contains 61-87 repeats, as opposed to the 12-44 repeats found in healthy individuals. A limitation to this test is that if the number of CAG repeats in an individual being tested falls between the healthy and pathogenic ranges (45-60 repeats), then the test cannot predict whether an individual will have MJD symptoms.

Currently there are no open research studies for otodental syndrome. Due to the rarity of this disease, current research is very limited.

The most recent research has involved case studies of the affected individuals and/or families, all of which show the specific phenotypic symptoms of otodental syndrome. Investigations on the effects of FGF3 and FADD have also been performed. These studies have shown successes in supporting previous studies that mutations to FGF3 and neighboring genes may cause the associated phenotypic abnormalities. According to recent studies involving zebrafish embryos, there is also support in that the FADD gene contributed to ocular coloboma symptoms as well.

Future research studies are required in order to better grasp the specific relationship between the gene involved and its effect on various tissues and organs such as teeth, eyes, and ear. Little is known and there is still much to be determined.

The severity of symptoms vary widely even for the same type of CMT. There have been cases of monozygotic twins with varying levels of disease severity, showing that identical genotypes are associated with different levels of severity (see penetrance). Some patients are able to live a normal life and are almost or entirely asymptomatic. A 2007 review stated that "Life expectancy is not known to be altered in the majority of cases".

One of the main methods of pinpointing a "NOTCH2" mutation that leads to HCS is through whole genome sequencing. This is then followed by exome capture by means of in-solution hybridization. The exome part of the genome consists of exons. Parallel sequencing follows the hybridization, which results in about 3.5 Gb of sequence data. These sequence data are then analyzed. Through sequence analysis and symptom presentation in HCS patients, this proves to be the most definitive method of diagnosis.

Treatment for autosomal dominant porencephaly type I is based on the symptoms that an individual is experiencing - for example, treatment of seizures with anticonvulsants. It is particularly important for individuals with this disorder and hypertension to control their blood pressure, as they are at higher risk of stroke. Other stroke prevention treatments include avoiding anticoagulants, smoking, and situations that may lead to head trauma.

Currently, no research has shown a higher prevalence of most leukodsytrophy types in any one place around the world. There is, however, a higher prevalence of the Canavan disease in the Jewish population for unknown reasons. 1 in 40 individuals of Ashkenazi Jewish descent are carriers of Canavan disease. This estimates to roughly 2.5%. Additionally, due to an autosomal recessive inheritance patterns, there is no significant difference found between affected males and affected females for most types of leukodystrophy including, but not limited to, metachromatic leukodystrophy, Krabbe disease, Canavan disease, and Alexander disease. The one exception to this is any type of leukodystrophy carried on a sex chromosome, such as X-linked adrenoleukodystrophy, which is carried on the X-chromosome. Because of the inheritance pattern of X-linked diseases, males are more often affected by this type of leukodystrophy, although female carriers are often symptomatic, though not as severely so as males. To date, there have been no found cases of a leukodystrophy carried on the Y chromosome.

In a sample of 19 children, a 1997 study found that 3 died before the age of 3, and 2 never learned to walk. The children had various levels of delayed development with developmental quotients from 60 to 85.

Currently, there is no cure for laminopathies and treatment is largely symptomatic and supportive. Physical therapy and/or corrective orthopedic surgery may be helpful for patients with muscular dystrophies. Cardiac problems that occur with some laminopathies may require a pacemaker. Treatment for neuropathies may include medication for seizures and spasticity.

The recent progress in uncovering the molecular mechanisms of toxic progerin formation in laminopathies leading to premature aging has opened up the potential for the development of targeted treatment. The farnesylation of prelamin A and its pathological form progerin is carried out by the enzyme farnesyl transferase. Farnesyl transferase inhibitors (FTIs) can be used effectively to reduce symptoms in two mouse model systems for progeria and to revert the abnormal nuclear morphology in progeroid cell cultures. Two oral FTIs, lonafarnib and tipifarnib, are already in use as anti-tumor medication in humans and may become avenues of treatment for children suffering from laminopathic progeria. Nitrogen-containing bisphosphate drugs used in the treatment of osteoporosis reduce farnesyldiphosphate production and thus prelamin A farnesylation. Testing of these drugs may prove them to be useful in treating progeria as well. The use of antisense oligonucleotides to inhibit progerin synthesis in affected cells is another avenue of current research into the development of anti-progerin drugs.

There are five sub-types of MJD that are characterized by the age of onset and range of symptoms.

The sub-types illustrate a wide variety of symptoms that patients can experience. However, assigning individuals to a specific sub-type of the disease is of limited clinical significance.

- Type I is distinguished by arrival between the ages of 10 and 30 and represents approximately 13% of individuals. It usually has fast development and severe rigidity and dystonia.

- Type II is the most common sub-type (approximately 57% of individuals with MJD ) and typically begins between 20 and 50 years of age . It has an intermediate progression and causes symptoms that include spasticity, exaggerated reflex responses and spastic gait, ataxia and upper motor neuron signs.

- Type III MJD has a slow progression. Patients typically have an onset between the ages of 40 and 70 and represent approximately 30% of MJD patients. Symptoms include muscle twitching, tingling, cramps, unpleasant sensations such as numbness, pain in the feet, hands and limbs and muscle atrophy. Nearly all patients experience a decline in their vision such as blurred vision, double vision, inability to control eye movements, and loss of capability to distinguish color. Some patients also experience Parkinsonian symptoms.

- Type IV is distinguished by Parkinsonian symptoms that respond particularly well to levodopa treatment.

- Type V appears to resemble Hereditary Spastic Paraplegia; however, more research is needed to conclude the relationship between Type V MJD and hereditary spastic paraplegia.

There is no pharmacological treatment for Roussy–Lévy syndrome.

Treatment options focus on palliative care and corrective therapy. Patients tend to benefit greatly from physical therapy (especially water therapy as it does not place excessive pressure on the muscles), while moderate activity is often recommended to maintain movement, flexibility, muscle strength and endurance.

Patients with foot deformities may benefit from corrective surgery, which, however, is usually a last resort. Most such surgeries include straightening and pinning the toes, lowering the arch, and sometimes, fusing the ankle joint to provide stability. Recovering from these surgeries is oftentimes long and difficult. Proper foot care including custom-made shoes and leg braces may minimize discomfort and increase function.

While no medicines are reported to treat the disorder, patients are advised to avoid certain medications as they may aggravate the symptoms.

Because this genetic anomaly is genetically linked, genetic counseling may be the only way to decrease occurrences of Cherubism. The lack of severe symptoms in the parents may be the cause of failure in recognizing the disorder. The optimal time to be tested for mutations is prior to having children. The disorder results from a genetic mutation, and this gene has been found to spontaneously mutate. Therefore, there may be no prevention techniques available.

Usually, a common form of treatment for the condition is a type of hand cream which moisturises the hard skin. However, currently the condition is incurable.

Diagnostic procedures that may reveal muscular disorders include direct clinical observations. This usually starts with the observation of bulk, possible atrophy or loss of muscle tone. Neuromuscular disease can also be diagnosed by testing the levels of various chemicals and antigens in the blood, and using electrodiagnostic medicine tests including electromyography (measuring electrical activity in muscles) and nerve conduction studies.

In neuromuscular disease evaluation, it is important to perform musculoskeletal and neurologic examinations. Genetic testing is an important part of diagnosing inherited neuromuscular conditions.

In terms of diagnosis of HNPP measuring nerve conduction velocity may give an indication of the presence of the disease.Other methods via which to ascertain the diagnosis of hereditary neuropathy with liability to pressure palsy are:

- Family history

- Genetic test

- Physical exam(lack of ankle reflex)

The disorder is characterized by absence or underdevelopment of the cerebellar vermis and a malformed brain stem (molar tooth sign), both of which can be visualized on a MRI scan. Together with this sign, the diagnosis is based on the physical symptoms and genetic testing for mutations. If the gene mutations have been identified in a family member, prenatal or carrier diagnosis can be pursued.

Joubert Syndrome is known to affect 1 in 80,000-100,000 newborns. Due to the variety of genes this disorder is affected by, it is likely to be under-diagnosed. It is commonly found in Ashkenazi Jewish, French-Canadians, and Hutterite ethnic populations. Most cases of Joubert syndrome are autosomal recessive - in these cases, both parents are either carriers or affected. Rarely, Joubert syndrome is inherited in an X-linked recessive pattern. In these cases, males are more commonly affected because affected males must have one X chromosome mutated, while affected females must have mutated genes on both X chromosomes.

Physical therapy is the predominant treatment of symptoms. Orthopedic shoes and foot surgery can be used to manage foot problems.