Electrodiagnostic testing (also called electrophysiologic) includes nerve conduction studies which involves stimulating a peripheral motor or sensory nerve and recording the response, and needle electromyography, where a thin needle or pin-like electrode is inserted into the muscle tissue to look for abnormal electrical activity.

Electrodiagnostic testing can help distinguish myopathies from neuropathies, which can help determine the course of further work-up. Most of the electrodiagnostic abnormalities seen in myopathies are also seen in neuropathies (nerve disorders). Electrodiagnostic abnormalities common to myopathies and neuropathies include; abnormal spontaneous activity (e.g., fibrillations, positive sharp waves, etc.) on needle EMG and, small amplitudes of the motor responses compound muscle action potential, or CMAP during nerve conduction studies. Many neuropathies, however, cause abnormalities of sensory nerve studies, whereas myopathies involve only the muscle, with normal sensory nerves. The most important factor distinguishing a myopathy from a neuropathy on needle EMG is the careful analysis of the motor unit action potential (MUAP) size, shape, and recruitment pattern.

There is substantial overlap between the electrodiagnostic findings the various types of myopathy. Thus, electrodiagnostic testing can help distinguish neuropathy from myopathy, but is not effective at distinguishing which specific myopathy is present, here muscle biopsy and perhaps subsequent genetic testing are required.

On examination of muscle biopsy material, the nuclear material is located predominantly in the center of the muscle cells, and is described as having any "myotubular" or "centronuclear" appearance. In terms of describing the muscle biopsy itself, "myotubular" or "centronuclear” are almost synonymous, and both terms point to the similar cellular-appearance among MTM and CNM. Thus, pathologists and treating physicians use those terms almost interchangeably, although researchers and clinicians are increasingly distinguishing between those phrases.

In general, a clinical myopathy and a muscle biopsy showing a centronuclear (nucleus in the center of the muscle cell) appearance would indicate a centronuclear myopathy (CNM). The most commonly diagnosed CNM is myotubular myopathy (MTM). However, muscle biopsy analysis alone cannot reliably distinguish myotubular myopathy from other forms of centronuclear myopathies, and thus genetic testing is required.

Diagnostic workup is often coordinated by a treating neurologist. In the United States, care is often coordinated through clinics affiliated with the Muscular Dystrophy Association.

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

In regards to the diagnosis of spinal and bulbar muscular atrophy, the "AR Xq12" gene is the focus. Many mutations are reported and identified as missense/nonsense, that can be identified with 99.9% accuracy. Test for this gene in the majority of affected patients yields the diagnosis.

A 2006 study followed 223 patients for a number of years. Of these, 15 died, with a median age of 65 years. The authors tentatively concluded that this is in line with a previously reported estimate of a shortened life expectancy of 10-15 years (12 in their data).

At present, Nemaline myopathy does not have a cure. Nemaline myopathy is a very rare disease that only effects 1 out of 50,000 on average, although recent studies show that this number is even smaller. There are a number of treatments to minimize the symptoms of the disease. The treatments and procedures to help patients with nemaline myopathy vary depending on the severity of the disease. A possible accommodation could be the use of a stabilizer, such as a brace. Other means include moderate stretching and moderate exercise to help target muscles maintain maximum health.

As people with NM grow and develop throughout their lives, it is important for them to see a variety of health professionals regularly, including a neurologist, physical therapist, and others, such as speech therapists and psychologists, to help both the patient and family adjust to everyday life.

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.

New research resources have become available for the NM community, such as the CMDIR (registry) and the CMD-TR (biorepository). These two resources connect families and individuals interested in participating in research with the scientists that aim to treat or cure NM. Some research on NM seeks to better understand the molecular effects the gene mutations have on muscle cells and the rest of the body and to observe any connections NM may have to other diseases and health complications.

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".

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

Harderoporphyria is a rare disorder of heme biosynthesis, inherited in an autosomal recessive manner caused by specific mutations in the "CPOX" gene. Mutations in "CPOX" usually cause hereditary coproporphyria, an acute hepatic porphyria, however the K404E mutation in a homozygous or compound heterozygous state with a null allele cause the more severe harderoporphyria. Harderoporphyria is the first known metabolic disorder where the disease phenotype depended on the type and location of the mutations in a gene associated with multiple disorders.

In contrast with other porphyrias, which typically present with either cutaneous lesions after exposure to sunlight or acute neurovisceral attack at any age (most commonly in adulthood), harderoporphyria is characterized by jaundice, anemia enlarged liver and spleen, often presenting in the neonatal period. Later in life, these individuals may present with photosensitivity similar to that found in cutaneous porphyrias.

Biochemically, harderoporphyria presents with a distinct pattern of increased harderoporphyrin (2-vinyl-4,6,7-tripropionic acid porphyrin) in urine and particularly in feces, a metabolite that is not seen in significant quantities in any other porphyria. Enzyme tests show markedly reduced activity of coproporphyrinogen oxidase, compared to both unaffected individuals and those affected with hereditary coproporphyria, consistent with recessive inheritance.

Harderoporphyria is a rare condition, with less than 10 cases reported worldwide. It may be underdiagnosed, as it does not have the typical presentation associated with a porphyria. It was identified as a variant type of coproporphyria in 1983, in a family with three children identified at birth with jaundice and hemolytic anemia. There is no standard treatment for harderoporphyria; care is mainly focused on the management of symptoms.

Suspicion of a chromosome abnormality is typically raised due to the presence of developmental delays or birth defects. Diagnosis of distal 18q- is usually made from 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 using amniocentesis or chorionic villus sampling.

Gillespie syndrome is a heterogeneous disorder, and can be inherited in either an autosomal dominant or recessive manner. Autosomal dominant inheritance indicates that the defective gene responsible for a disorder is located on an autosome, and only one copy of the gene is sufficient to cause the disorder, when inherited from a parent who has the disorder.

Autosomal recessive inheritance means the defective gene responsible for the disorder is located on an autosome, but two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.

PAX6 gene analysis can also be helpful to distinguish between autosomal dominant aniridia and Gillespie syndrome. However Atypical Gillespie syndrome is associated mutation with "PAX6 gene".

To illucidate the underlying genetic defects karyotyping and the search for de novo translocations especially of chromosome X and 11 should be performed.

Aside from observing the symptoms characteristic of X-linked thrombocytopenia in infancy (easy bruising, mild anemia, mucosal bleeding), molecular genetic testing would be done to confirm the diagnosis. Furthermore, flow cytometry or western blotting would be used to test for decreased or absent amounts of WASp. Family history would also assist in diagnosis, with specific attention to maternally related males with "WAS"-related disorders. Because "WAS"-related disorders are phenotypically similar, it is important to confirm the absence of the diagnostic criteria for Wiskoff-Aldrich syndrome at the outset. These diagnostic criteria include eczema, lymphoma, autoimmune disorder, recurrent bacterial or viral infections, family history of maternally related males with a "WAS"-related disorder, and absent or decreased "WASp". X-linked congenital neutropenia can be diagnostically distinguished from XLT with persistent neutropenia, arrested development of the bone marrow, and normal "WASp" expression.

About 92% of pregnancies in Europe with a diagnosis of Down syndrome are terminated. In the United States, termination rates are around 67%, but this rate varied from 61% to 93% among different populations evaluated. When nonpregnant people are asked if they would have a termination if their fetus tested positive, 23–33% said yes, when high-risk pregnant women were asked, 46–86% said yes, and when women who screened positive are asked, 89–97% say yes.

Recent studies have found that the life expectancy of males with XLT is not significantly affected. Individuals with XLT typically experience milder symptoms than those with other "WAS"-related disorders. For this reason, the long term prognosis for individuals with XLT is generally positive as long as symptoms are managed appropriately. Enhanced treatment methods in the past two decades have significantly improved the prognosis as well.

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.

The diagnosis can often be suspected based on the child's physical appearance at birth. An analysis of the child's chromosomes is needed to confirm the diagnosis, and to determine if a translocation is present, as this may help determine the risk of the child's parents having further children with Down syndrome. Parents generally wish to know the possible diagnosis once it is suspected and do not wish pity.

Cytogenetic analysis for fragile X syndrome was first available in the late 1970s when diagnosis of the syndrome and carrier status could be determined by culturing cells in a folate deficient medium and then assessing for "fragile sites" (discontinuity of staining in the region of the trinucleotide repeat) on the long arm of the X chromosome. This technique proved unreliable, however, as the fragile site was often seen in less than 40% of an individual's cells. This was not as much of a problem in males, but in female carriers, where the fragile site could generally only be seen in 10% of cells, the mutation often could not be visualised.

Since the 1990s, more sensitive molecular techniques have been used to determine carrier status. The fragile X abnormality is now directly determined by analysis of the number of CGG repeats using polymerase chain reaction (PCR) and methylation status using Southern blot analysis. By determining the number of CGG repeats on the X chromosome, this method allows for more accurate assessment of risk for premutation carriers in terms of their own risk of fragile X associated syndromes, as well as their risk of having affected children. Because this method only tests for expansion of the CGG repeat, individuals with FXS due to missense mutations or deletions involving "FMR1" will not be diagnosed using this test and should therefore undergo sequencing of the FMR1 gene if there is clinical suspicion of FXS.

Prenatal testing with chorionic villus sampling or amniocentesis allows diagnosis of FMR1 mutation while the fetus is in utero and appears to be reliable.

Early diagnosis of fragile X syndrome or carrier status is important for providing early intervention in children or fetuses with the syndrome, and allowing genetic counselling with regards to the potential for a couple's future children to be affected. Most parents notice delays in speech and language skills, difficulties in social and emotional domains as well as sensitivity levels in certain situations with their children.

The basic tests performed when an immunodeficiency is suspected should include a full blood count (including accurate lymphocyte and granulocyte counts) and immunoglobulin levels (the three most important types of antibodies: IgG, IgA and IgM).

Other tests are performed depending on the suspected disorder:

- Quantification of the different types of mononuclear cells in the blood (i.e. lymphocytes and monocytes): different groups of T lymphocytes (dependent on their cell surface markers, e.g. CD4+, CD8+, CD3+, TCRαβ and TCRγδ), groups of B lymphocytes (CD19, CD20, CD21 and Immunoglobulin), natural killer cells and monocytes (CD15+), as well as activation markers (HLA-DR, CD25, CD80 (B cells).

- Tests for T cell function: skin tests for delayed-type hypersensitivity, cell responses to mitogens and allogeneic cells, cytokine production by cells

- Tests for B cell function: antibodies to routine immunisations and commonly acquired infections, quantification of IgG subclasses

- Tests for phagocyte function: reduction of nitro blue tetrazolium chloride, assays of chemotaxis, bactericidal activity.

Due to the rarity of many primary immunodeficiencies, many of the above tests are highly specialised and tend to be performed in research laboratories.

Criteria for diagnosis were agreed in 1999. For instance, an antibody deficiency can be diagnosed in the presence of low immunoglobulins, recurrent infections and failure of the development of antibodies on exposure to antigens. The 1999 criteria also distinguish between "definitive", "probable" and "possible" in the diagnosis of primary immunodeficiency. "Definitive" diagnosis is made when it is likely that in 20 years, the patient has a >98% chance of the same diagnosis being made; this level of diagnosis is achievable with the detection of a genetic mutation or very specific circumstantial abnormalities. "Probable" diagnosis is made when no genetic diagnosis can be made, but the patient has all other characteristics of a particular disease; the chance of the same diagnosis being made 20 years later is estimated to be 85-97%. Finally, a "possible" diagnosis is made when the patient has only some of the characteristics of a disease are present, but not all.

Treatments exist for the various symptoms associated with XXXY syndrome. Testosterone therapy, which is giving affected individuals doses of testosterone on a regular basis, has been shown to reduce aggressive behavior in these patients. But, this therapy has also been associated with negative side effects: worsening of behavior, and osteoporosis. Not all individuals are applicable for testosterone therapy, as the best results are often achieved when dosage begins at the initiation of puberty, and these individuals are often diagnosed at a later age, or not at all. Testosterone therapy has been shown to have no positive effect on fertility.

Consideration of the psychological phenotype of individuals with XXXY should be taken into account when treating these patients, because these traits affect compliance with treatments. When caught early, Taurodontism can be treated with a root canal and is often successful. Appropriate planning to avoid Taurodontism is possible, but this syndrome must be diagnosed early, which is not common. Taurodontism can often be detected as a symptom of XXXY syndrome before other characteristics develop, and can be an early indicator for it. Surgical treatments to correct joint problems, such as hip dysplasia are common, and are often successful alongside physiotherapy.

Those with XXXY syndrome can also attend speech therapy. This form of therapy helps patients to understand and produce more complex language. Those with XXXY syndrome tend to experience more severe speech delays, so this form of treatment can be very beneficial to them, and can help them to communicate better with other people.

Since hypotonia is common in those with this syndrome, physical therapy can also be helpful. This form of therapy may help these individuals develop muscle tone, and increase balance and coordination.

Turner syndrome can be diagnosed postnatally at any age. Often, it is diagnosed at birth due to heart problems, an unusually wide neck or swelling of the hands and feet. However, it is also common for it to go undiagnosed for several years, typically until the girl reaches the age of puberty/adolescence and she fails to develop properly (the changes associated with puberty do not occur). In childhood, a short stature can be indicative of Turner syndrome.

A test called a karyotype, also known as a chromosome analysis, analyzes the chromosomal composition of the individual. This is the test of choice to diagnose Turner 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.

A survey of 10,000 American households revealed that the prevalence of diagnosed primary immunodeficiency approaches 1 in 1200. This figure does not take into account people with mild immune system defects who have not received a formal diagnosis.

Milder forms of primary immunodeficiency, such as selective immunoglobulin A deficiency, are fairly common, with random groups of people (such as otherwise healthy blood donors) having a rate of 1:600. Other disorders are distinctly more uncommon, with incidences between 1:100,000 and 1:2,000,000 being reported.

Management of AIS is currently limited to symptomatic management; no method is currently available to correct the malfunctioning androgen receptor proteins produced by "AR" gene mutations. Areas of management include sex assignment, genitoplasty, gonadectomy in relation to tumor risk, hormone replacement therapy, genetic counseling, and psychological counseling.