Diagnosis of Bruck syndrome must distinguish the association of contractures and skeletal fragility. Ultrasound is used for prenatal diagnosis. The diagnosis of a neonate bears resemblance to arthrogryposis multiplex congenital, and later in childhood to osteogenesis imperfecta.

No treatment is available for most of these disorders. Mannose supplementation relieves the symptoms in PMI-CDG (CDG-Ib) for the most part, even though the hepatic fibrosis may persist. Fucose supplementation has had a partial effect on some SLC35C1-CDG (CDG-IIc or LAD-II) patients.

Medical diagnosis of CGL can be made after observing the physical symptoms of the disease: lipoatrophy (loss of fat tissues) affecting the trunk, limbs, and face; hepatomegaly; acromegaly; insulin resistance; and high serum levels of triglycerides. Genetic testing can also confirm the disease, as mutations in the AGPAT2 gene is indicative of CGL1, a mutation in the BSCL2 gene is indicative of CGL2, and mutations in the CAV1 and PTRF genes are indicative of CGL3 and CGL4 respectively. Physical diagnosis of CGL is easier, as CGL patients are recognizable from birth, due to their extreme muscular appearance, which is caused by the absence of subcutaneous fat.

CGL3 patients have serum creatine kinase concentrations much higher than normal (2.5 to 10 times the normal limit). This can be used to diagnose type 3 patients and differentiate them from CGL 1 and 2 without mapping their genes. Additionally, CGL3 patients have low muscle tone when compared with other CGL patients.

The diagnosis of ML is based on clinical symptoms, a complete medical history, and certain laboratory tests.

Amniocentesis or chorionic villus sampling can be used to screen for the disease before birth. After birth, urine tests, along with blood tests and skin biopsies can be used to diagnose Schindler disease. Genetic testing is also always an option, since different forms of Schindler disease have been mapped to the same gene on chromosome 22; though different changes (mutations) of this gene are responsible for the infantile- and adult-onset forms of the disease.

Diagnosis of MSS is based on clinical symptoms, magnetic resonance imaging (MRI) of the brain (cerebellar atrophy particularly involving the cerebellar vermis), and muscle biopsy.

It can be associated with mutations of the SIL1 gene, and a mutation can be found in about 50% of cases.

Differential diagnosis includes Congenital Cataracts Facial Dysmorphism Neuropathy (CCFDN), Marinesco–Sjögren like syndrome with chylomicronemia, carbohydrate deficient glycoprotein syndromes, Lowe syndrome, and mitochondrial disease.

Diagnosis often can be made through clinical examination and urine tests (excess mucopolysaccharides are excreted in the urine). Enzyme assays (testing a variety of cells or body fluids in culture for enzyme deficiency) are also used to provide definitive diagnosis of one of the mucopolysaccharidoses. Prenatal diagnosis using amniocentesis and chorionic villus sampling can verify if a fetus either carries a copy of the defective gene or is affected with the disorder. Genetic counseling can help parents who have a family history of the mucopolysaccharidoses determine if they are carrying the mutated gene that causes the disorders.

Individuals presenting with Type III galactosemia must consume a lactose- and galactose-restricted diet devoid of dairy products and mucilaginous plants. Dietary restriction is the only current treatment available for GALE deficiency. As glycoprotein and glycolipid metabolism generate endogenous galactose, however, Type III galactosemia may not be resolved solely through dietary restriction.

When suspected, the diagnosis can be confirmed by laboratory measurement of IgA level in the blood. SigAD is an IgA level < 7 mg/dL with normal IgG and IgM levels (reference range 70–400 mg/dl for adults; children somewhat less).

Until more molecular and clinical studies are performed there will be no way to prevent the disease. Treatments are directed towards alleviating the symptoms. To treat the disease it is crucial to diagnose it properly. Orthopedic therapy and fracture management are necessary to reduce the severity of symptoms. Bisphosphonate drugs are also an effective treatment.

Infants with Schindler disease tend to die within 4 years of birth, therefore, treatment for this form of the disease is mostly palliative. However, Type II Schindler disease, with its late onset of symptoms, is not characterized by neurological degeneration. There is no known cure for Schindler disease, but bone marrow transplants have been trialed, as they have been successful in curing other glycoprotein disorders.

Treatment for MSS is symptomatic and supportive including physical and occupational therapy, speech therapy, and special education. Cataracts must be removed when vision is impaired, generally in the first decade of life. Hormone replacement therapy is needed if hypogonadism is present.

The condition is diagnosed by blood tests in the laboratory when it is noted that special blood clotting test are abnormal. Specifically prothrombin time (PT) or activated partial thromboplastin time(aPTT) are prolonged. The diagnosis is confirmed by an assay detecting very low or absent FXII levels.

The FXII (F12) gene is found on chromosome 5q33-qter.

In hereditary angioedema type III an increased activity of factor XII has been described.

CGL patients have to maintain a strict diet for life, as their excess appetite will cause them to overeat. Carbohydrate intake should be restricted in these patients. To avoid chylomicronemia, CGL patients with hypertriglyceridemia need to have a diet very low in fat. CGL patients also need to avoid total proteins, trans fats, and eat high amounts of soluble fiber to avoid getting high levels of cholesterol in the blood.

Mutations in several genes have been associated with the traditional clinical syndromes, termed muscular dystrophy-dystroglycanopathies (MDDG). A new nomenclature based on clinical severity and genetic cause was recently proposed by OMIM. The severity classifications are A (severe), B (intermediate), and C (mild). The subtypes are numbered one to six according to the genetic cause, in the following order: (1) POMT1, (2) POMT2, (3) POMGNT1, (4) FKTN, (5) FKRP, and (6) LARGE.

Most common severe types include:

The diagnosis of this condition can be done via the following:

- Flow cytometry

- Bleeding time analysis

Currently there is no cure for these disorders. Medical care is directed at treating systemic conditions and improving the person's quality of life. Physical therapy and daily exercise may delay joint problems and improve the ability to move.

Changes to the diet will not prevent disease progression, but limiting milk, sugar, and dairy products has helped some individuals experiencing excessive mucus.

Surgery to remove tonsils and adenoids may improve breathing among affected individuals with obstructive airway disorders and sleep apnea. Sleep studies can assess airway status and the possible need for nighttime oxygen. Some patients may require surgical insertion of an endotrachial tube to aid breathing. Surgery can also correct hernias, help drain excessive cerebrospinal fluid from the brain, and free nerves and nerve roots compressed by skeletal and other abnormalities. Corneal transplants may improve vision among patients with significant corneal clouding.

Enzyme replacement therapy (ERT) are currently in use or are being tested. Enzyme replacement therapy has proven useful in reducing non-neurological symptoms and pain. Currently BioMarin Pharmaceutical produces enzyme replacement therapies for MPS type I and VI. Aldurazyme is an enzymatic replacement therapy for alpha-L-iduronidase produced by BioMarin for use in Type I MPS. In July 2006, the United States Food and Drug Administration approved a synthetic version of I2S produced by Shire Pharmaceuticals Group, called Elaprase, as a treatment for MPS type II (Hunter syndrome).

Bone marrow transplantation (BMT) and umbilical cord blood transplantation (UCBT) have had limited success in treating the mucopolysaccharidoses. Abnormal physical characteristics, except for those affecting the skeleton and eyes, may be improved, but neurologic outcomes have varied. BMT and UCBT are high-risk procedures and are usually performed only after family members receive extensive evaluation and counseling.

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Prognosis is excellent, although there is an association with autoimmune disease. Of note, selective IgA deficiency can complicate the diagnosis of one such condition, celiac disease, as the deficiency masks the high levels of certain IgA antibodies usually seen in celiac disease.

As opposed to the related condition CVID, selective IgA deficiency is not associated with an increased risk of cancer.

Patients with Selective IgA deficiency are at risk of anaphylaxis from blood transfusions. These patients should receive IgA free containing blood products and ideally blood from IgA-deficient donors.

There are 2 forms of epimerase deficiency: benign RBC deficiency and Severe liver deficiency. Severe form is similar to galactosemia.

The differential diagnosis is quite extensive and includes

- Buschke–Fischer–Brauer disease

- Curth–Macklin ichthyosis

- Gamborg Nielsen syndrome

- Greither disease

- Haber syndrome

- Hereditary punctate palmoplantar keratoderma

- Jadassohn–Lewandowsky syndrome

- Keratosis follicularis spinulosa decalvans

- Keratosis linearis with ichthyosis congenital and sclerosing keratoderma syndrome

- Meleda disease

- Mucosa hyperkeratosis syndrome

- Naegeli–Franceschetti–Jadassohn syndrome

- Naxos disease

- Olmsted syndrome

- Palmoplantar keratoderma and leukokeratosis anogenitalis

- Pandysautonomia

- Papillomatosis of Gougerot and Carteaud

- Papillon–Lefèvre syndrome

- Punctate porokeratotic keratoderma

- Richner–Hanhart syndrome

- Schöpf–Schulz–Passarge syndrome

- Unna Thost disease

- Vohwinkel syndrome

- Wong's dermatomyositis

In congenital FXII deficiency treatment is not necessary. In acquired FXII deficiency the underlying problem needs to be addressed.

Children with Maroteaux–Lamy syndrome usually have normal intellectual development but share many of the physical symptoms found in Hurler syndrome. Caused by the deficient enzyme N-acetylgalactosamine 4-sulfatase, Maroteaux–Lamy syndrome has a variable spectrum of severe symptoms. Neurological complications include clouded corneas, deafness, thickening of the dura (the membrane that surrounds and protects the brain and spinal cord), and pain caused by compressed or traumatized nerves and nerve roots.

Signs are revealed early in the affected child's life, with one of the first symptoms often being a significantly prolonged age of learning how to walk. By age 10 children have developed a shortened trunk, crouched stance, and restricted joint movement. In more severe cases, children also develop a protruding abdomen and forward-curving spine. Skeletal changes (particularly in the pelvic region) are progressive and limit movement. Many children also have umbilical hernia or inguinal hernias. Nearly all children have some form of heart disease, usually involving valve dysfunction.

An enzyme replacement therapy, galsulfase (Naglazyme), was tested on patients with Maroteaux–Lamy syndrome and was successful in that it improved growth and joint movement. An experiment was then carried out to see whether an injection of the missing enzyme into the hips would help the range of motion and pain. At a cost of $365,000 a year, Naglazyme is one of the world's most expensive drugs.

The fifth type of hyper-IgM syndrome has been characterized in three patients from France and Japan. The symptoms are similar to hyper IgM syndrome type 2, but the AICDA gene is intact. These three patients instead had mutations in the catalytic domain of uracil-DNA glycosylase, an enzyme that removes uracil from DNA. In both type 2 and type 5 hyper-IgM syndromes, the patients are profoundly deficient in IgG and IgA because the B cells can't carry out the recombination steps necessary to class-switch.

Griscelli syndrome is a rare autosomal recessive disorder characterized by albinism (hypopigmentation) with immunodeficiency, that usually causes death by early childhood.

Howel–Evans syndrome is an extremely rare condition involving thickening of the skin in the palms of the hands and the soles of the feet (hyperkeratosis). This familial disease is associated with a high lifetime risk of esophageal cancer. For this reason, it is sometimes known as tylosis with oesophageal cancer (TOC).

The condition is inherited in an autosomal dominant manner, and it has been linked to a mutation in the "RHBDF2" gene. It was first described in 1958.