Diagnostic techniques for this condition can be done to offer a DDx, via lectin histochemistry to distinguish between α-mannosidosis and beta-mannosidosis.

A diagnosis of beta-mannosidosis is suspected based on the persons clinical presentation. Urine testing to identify abnormal oligosaccharides is a useful screening test, and enzymatic analysis or molecular testing can be used for confirmation.

The use of biochemical testing for the detection of carriers is technically demanding and not often used. Biochemical analyses that have been performed on hair bulbs from at risk women have had a small number of both false positive and false negative outcomes. If only a suspected carrier female is available for mutation testing, it may be appropriate to grow her lymphocytes in 6-thioguanine (a purine analogue), which allows only HGPRT-deficient cells to survive. A mutant frequency of 0.5–5.0 × 10 is found in carrier females, while a non-carrier female has a frequency of 1–20 × 10. This frequency is usually diagnostic by itself.

Molecular genetic testing is the most effective method of testing, as HPRT1 is the only gene known to be associated with LNS. Individuals who display the full Lesch–Nyhan phenotype all have mutations in the HPRT1 gene. Sequence analysis of mRNA is available clinically and can be utilized in order to detect HPRT1 mutations in males affected with Lesch–Nyhan syndrome. Techniques such as RT-PCR, multiplex genomic PCR, and sequence analysis (cDNA and genomic DNA), used for the diagnosis of genetic diseases, are performed on a research basis. If RT-PCR tests result in cDNA showing the absence of an entire exon or exons, then multiplex genomic PCR testing is performed. Multiplex genomic PCR testing amplifies the nine exons of the HPRT1 gene as eight PCR products. If the exon in question is deleted, the corresponding band will be missing from the multiplex PCR. However, if the exon is present, the exon is sequenced to identify the mutation, therefore causing exclusion of the exon from cDNA. If no cDNA is created by RT-PCR, then multiplex PCR is performed on the notion that most or all of the gene is obliterated.

The urate to creatinine (breakdown product of creatine phosphate in muscle) concentration ratio in urine is elevated. This is a good indicator of acid overproduction. For children under ten years of age with LNS, a urate to creatinine ratio above two is typically found. Twenty-four-hour urate excretion of more than 20 mg/kg is also typical but is not diagnostic. Hyperuricemia (serum uric acid concentration of >8 mg/dL) is often present but not reliable enough for diagnosis. Activity of the HGPRT enzyme in cells from any type of tissue (e.g., blood, cultured fibroblasts, or lymphoblasts) that is less than 1.5% of normal enzyme activity confirms the diagnosis of Lesch–Nyhan syndrome. Molecular genetic studies of the HPRT gene mutations may confirm diagnosis, and are particularly helpful for subsequent 'carrier testing' in at-risk females such as close family relatives on the female side.

The clinical presentation of ALD can vary greatly, making diagnosis difficult. With the variety of phenotypes, clinical suspicion of ALD can result from a variety of different presentations. Symptoms vary based on the disease phenotype, and even within families or between twins. When ALD is suspected based on clinical symptoms, the initial testing usually includes plasma very long chain fatty acid (VLCFA) determination using gas chromatography-mass spectrometry. The concentration of unsaturated VLCFA, particularly 26 carbon chains is significantly elevated in males with ALD, even prior to the development of other symptoms. Confirmation of ALD after positive plasma VLCFA determination usually involves molecular genetic analysis of "ABCD1". In females, where plasma VLCFA measurement is not always conclusive (some female carriers will have normal VLCFA in plasma), molecular analysis is preferred, particularly in cases where the mutation in the family is known. Although the clinical phenotype is highly variable among affected males, the elevations of VLCFA are present in all males with an "ABCD1" mutation.

Because the characteristic elevations associated with ALD are present at birth, well before any symptoms are apparent, there have been methods developed in the interests of including it in newborn screening programs. One of the difficulties with ALD as a disease included in universal newborn screening is the difficulty in predicting the eventual phenotype that an individual will express. The accepted treatment for affected boys presenting with the cerebral childhood form of the disease is a bone marrow transplant, a procedure which carries significant risks. However, because most affected males will demonstrate adrenal insufficiency, early discovery and treatment of this symptom could potentially prevent complications and allow these patients to be monitored for other treatment in the future, depending on the progression of their disease.

The Loes score is a rating of the severity of abnormalities in the brain found on MRI. It ranges from 0 to 34, based on a point system derived from the location and extent of disease and the presence of atrophy in the brain, either localized to specific points or generally throughout the brain. A Loes score of 0.5 or less is classified as normal, while a Loes score of 14 or greater is considered severe. It was developed by neuroradiologist Daniel J. Loes MD and is an important tool in assessing disease progression and the effectiveness of therapy.

McLeod syndrome is one of only a few disorders in which acanthocytes may be found on the peripheral blood smear. Blood evaluation may show signs of hemolytic anemia. Elevated creatine kinase can be seen with myopathy in McLeod syndrome.

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.

In individuals with marked hyperammonemia, a urea cycle disorder is usually high on the list of possible causes. While the immediate focus is lowering the patient's ammonia concentrations, identifying the specific cause of increased ammonia levels is key as well.

Diagnostic testing for OTC deficiency, or any individual with hyperammonemia involves plasma and urine amino acid analysis, urine organic acid analysis (to identify the presence or absence of orotic acid, as well as rule out an organic acidemia) and plasma acylcarnitines (will be normal in OTC deficiency, but can identify some other causes of hyperammonemia). An individual with untreated OTC deficiency will show decreased citrulline and arginine concentrations (because the enzyme block is proximal to these intermediates) and increased orotic acid. The increased orotic acid concentrations result from the buildup of carbamoyl phosphate. This biochemical phenotype (increased ammonia, low citrulline and increased orotic acid) is classic for OTC deficiency, but can also be seen in neonatal presentations of ornithine aminotransferase deficiency. Only severely affected males consistently demonstrate this classic biochemical phenotype.

Heterozygous females can be difficult to diagnose. With the rise of sequencing techniques, molecular testing has become preferred, particularly when the disease causing mutations in the family are known. Historically, heterozygous females were often diagnosed using an allopurinol challenge. In a female with reduced enzyme activity, an oral dose of allopurinol would be metabolized to oxypurinol ribonucleotide, which blocks the pyrimidine biosynthetic pathway. When this induced enzymatic block is combined with reduced physiologic enzyme activity as seen in heterozygotes, the elevation of orotic acid could be used to differentiate heterozygotes from unaffected individuals. This test was not universally effective, as it had both false negative and false positive results.

Ornithine transcarbamylase is only expressed in the liver, thus performing an enzyme assay to confirm the diagnosis requires a liver biopsy. Before molecular genetic testing was commonly available, this was one of the only methods for confirmation of a suspected diagnosis. In cases where prenatal diagnosis was requested, a fetal liver biopsy used to be required to confirm if a fetus was affected. Modern molecular techniques have eliminated this need, and gene sequencing is now the preferred method of diagnosis in asymptomatic family members after the diagnosis has been confirmed in a proband.

A 1999 retrospective study of 74 cases of neonatal onset found that 32 (43%) patients died during their first hyperammonemic episode. Of those who survived, less than 20% survived to age 14. Few of these patients received liver transplants.

A typical patient with severe McLeod syndrome that begins in adulthood lives for an additional 5 to 10 years. Patients with cardiomyopathy have elevated risk for congestive heart failure and sudden cardiac death. The prognosis for a normal life span is often good in some patients with mild neurological or cardiac sequelae.

Not all genetic disorders directly result in death, however there are no known cures for genetic disorders. Many genetic disorders affect stages of development such as Down syndrome. While others result in purely physical symptoms such as muscular dystrophy. Other disorders, such as Huntington's disease show no signs until adulthood. During the active time of a genetic disorder, patients mostly rely on maintaining or slowing the degradation of quality of life and maintain patient autonomy. This includes physical therapy, pain management, and may include a selection of alternative medicine programs.

The diagnosis of Wilson–Turner syndrome is based upon a clinical evaluation, a detailed patient history, and identification of characteristic features. Molecular genetic testing for mutations in the HDAC8 gene is now available to confirm the diagnosis.

A 2007 study followed 112 individuals for a mean of 12 years (mean age 25.3, range 12–71). No patient died during follow-up, but several required medical interventions. The mean final heights were 167 and 153 cm for men and women, respectively, which is approximately 2 standard deviations below normal.

Treatment of the adrenal insufficiency that can accompany any of the common male phenotypes of ALD does not resolve any of the neurological symptoms. Hormone replacement is standard for ALD patients demonstrating adrenal insufficiency. Adrenal insufficiency does not resolve with successful transplant; most patients still require hormone replacement.

The Wilson–Turner syndrome is characterized by mild to moderate range of intellectual disability, obesity, tapered fingers, and mood swings. Males also suffer from gynecomastia and hypogonadism. In order to be diagnosed with Wilson-Turner Syndrome, male patients must suffer from intellectual disability, obesity, and gynecomastia. Females do not necessarily have to have noticeable phenotype but can be diagnosed with this disorder by studying her family history and identifying others with the disorder. It has been noted that children with Wilson-Turner Syndrome will display speech development delay and excessive drooling. Males can be confirmed by testing androgen levels. Female carriers will show silencing of the gene a complex X inactivation.

First trimester ultrasound of noonan syndrome reveals nuchal oedema / cystic hygroma almost same as seen in Turner syndrome. Follow up scans may shows clinical features that already described above.

A study shows this disease is also associated with hepato splenomegaly with renal anomalies including malrotation and solitary kidney. A rare incidence of choledochal cyst is also reported as well.

The diagnosis of this syndrome can be made on clinical examination and perinatal autopsy.

Koenig and Spranger (1986) noted that eye lesions are apparently nonobligatory components of the syndrome. The diagnosis of Fraser syndrome should be entertained in patients with a combination of acrofacial and urogenital malformations with or without cryptophthalmos. Thomas et al. (1986) also emphasized the occurrence of the cryptophthalmos syndrome without cryptophthalmos and proposed diagnostic criteria for Fraser syndrome. Major criteria consisted of cryptophthalmos, syndactyly, abnormal genitalia, and positive family history. Minor criteria were congenital malformation of the nose, ears, or larynx, cleft lip and/or palate, skeletal defects, umbilical hernia, renal agenesis, and mental retardation. Diagnosis was based on the presence of at least 2 major and 1 minor criteria, or 1 major and 4 minor criteria.

Boyd et al. (1988) suggested that prenatal diagnosis by ultrasound examination of eyes, digits, and kidneys should detect the severe form of the syndrome. Serville et al. (1989) demonstrated the feasibility of ultrasonographic diagnosis of the Fraser syndrome at 18 weeks' gestation. They suggested that the diagnosis could be made if 2 of the following signs are present: obstructive uropathy, microphthalmia, syndactyly, and oligohydramnios. Schauer et al. (1990) made the diagnosis at 18.5 weeks' gestation on the basis of sonography. Both the female fetus and the phenotypically normal father had a chromosome anomaly: inv(9)(p11q21). An earlier born infant had Fraser syndrome and the same chromosome 9 inversion.

Van Haelst et al. (2007) provided a revision of the diagnostic criteria for Fraser syndrome according to Thomas et al. (1986) through the addition of airway tract and urinary tract anomalies to the major criteria and removal of mental retardation and clefting as criteria. Major criteria included syndactyly, cryptophthalmos spectrum, urinary tract abnormalities, ambiguous genitalia, laryngeal and tracheal anomalies, and positive family history. Minor criteria included anorectal defects, dysplastic ears, skull ossification defects, umbilical abnormalities, and nasal anomalies. Cleft lip and/or palate, cardiac malformations, musculoskeletal anomalies, and mental retardation were considered uncommon. Van Haelst et al. (2007) suggested that the diagnosis of Fraser syndrome can be made if either 3 major criteria, or 2 major and 2 minor criteria, or 1 major and 3 minor criteria are present in a patient.

A combination of clinical findings and laboratory tests are used to diagnose Rabson-Mendenhall Syndrome. Initially, individuals are screened for symptoms and have their blood sugar levels analyzed. The two principle tests used to determine insulin resistance are the fasting plasma glucose test (FPG) and the oral glucose tolerance test (GTT). Results from a patient with severe insulin resistance will show values exceeding healthy ranges (≤99 mg/dL for FPG and ≤139 mg/dL for GTT) by over 50 units. A genetic history is also established to determine risk of recurrence in the family. Based on the combination of these findings, an appropriate diagnosis is made.

Rabson–Mendenhall syndrome is commonly associated with Donohue syndrome, also known as "Leprechaunism". Both diseases are autosomal recessive disorders caused by mutations on chromosome 19. Severe insulin resistance and an irregular enlargement of the genitalia are also overlapping symptoms.

X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed in males (who are necessarily hemizygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation, see zygosity.

X-linked inheritance means that the gene causing the trait or the disorder is located on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. Carrier females who have only one copy of the mutation do not usually express the phenotype, although differences in X chromosome inactivation can lead to varying degrees of clinical expression in carrier females since some cells will express one X allele and some will express the other. The current estimate of sequenced X-linked genes is 499 and the total including vaguely defined traits is 983.

Some scholars have suggested discontinuing the terms dominant and recessive when referring to X-linked inheritance due to the multiple mechanisms that can result in the expression of X-linked traits in females, which include cell autonomous expression, skewed X-inactivation, clonal expansion, and somatic mosaicism.

Treatments for Glycerol Kinase Deficiency are targeted to treat the symptoms because there are no permanent treatments for this disease. The main way to treat these symptoms is by using corticosteroids, glucose infusion, or mineralocorticoids. Corticosteroids are steroid hormones that are naturally produced in the adrenal glands. These hormones regulate stress responses, carbohydrate metabolism, blood electrolyte levels, as well as other uses. The mineralocorticoids, such as aldosterone control many electrolyte levels and allow the kidneys to retain sodium. Glucose infusion is coupled with insulin infusion to monitor blood glucose levels and keep them stable.

Due to the multitude of varying symptoms of this disease, there is no specific treatment that will cure this disease altogether. The symptoms can be treated with many different treatments and combinations of medicines to try to find the correct combination to offset the specific symptoms. Everyone with Glycerol Kinase Deficiency has varying degrees of symptoms and thereby requires different medicines to be used in combination to treat the symptoms; however, this disease is not curable and the symptoms can only be managed, not treated fully.

In humans, generally men are affected and women are carriers for two reasons. The first is the simple statistical fact that if the X-chromosomes is a population that carry a particular X-linked mutation at a frequency of 'f' (for example, 1%) then that will be the frequency that men are likely to express the mutation (since they have only one X), while women will express it at a frequency of f (for example 1% * 1% = 0.01%) since they have two X's and hence two chances to get the normal allele. Thus, X-linked mutations tend to be rare in women. The second reason for female rarity is that women who "express" the mutation must have two X chromosomes that carry the trait and they necessarily got one from their father, who would have also expressed the trait because he only had one X chromosome in the first place. If the trait lowers the probability of fathering a child or induces the father to only have children with women who aren't carriers (so as not to create daughters who are carriers rather than expressers and then only if no genetic screening is used) then women become even "less" likely to express the trait.

At present, treatment for proximal 18q- is symptomatic, meaning that the focus is on treating the signs and symptoms of the condition as they arise.

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.

Glycerol Kinase Deficiency (GKD) is an X-linked recessive enzyme defect that is heterozygous in nature. Three clinically distinct forms of this deficiency have been proposed, namely infantile, juvenile, and adult. National Institutes of Health and its Office of Rare Diseases Research (ORDR) branch classifies GKD as a rare disease, known to affect fewer than 200,000 individuals in the United States. The responsible gene lies in a region containing genes in which deletions can cause Duchenne muscular dystrophy and adrenal hypoplasia congenita. Combinations of these three genetic defects including GKD are addressed medically as Complex GKD.

Wolf–Hirschhorn syndrome is a microdeletion syndrome caused by a deletion within HSA band 4p16.3 of the short arm of chromosome 4, particularly in the region of and . About 87% of cases represent a "de novo" deletion, while about 13% are inherited from a parent with a chromosome translocation. In the cases of familial translocation, there is a 2 to 1 excess of maternal transmission. Of the "de novo" cases, 80% are paternally derived. Severity of symptoms and expressed phenotype differ based on the amount of genetic material deleted. The critical region for determining the phenotype is at 4p16.3 and can often be detected through genetic testing and fluorescence in situ hybridization (FISH). Genetic testing and genetic counseling is offered to affected families.