[7] Associated conditions include kidney problems, schizophrenia, hearing loss and autoimmune disorders such as rheumatoid arthritis or Graves' disease.

[citation needed] Affected individuals may also have other kinds of birth defects including kidney abnormalities and significant feeding difficulties as babies.

[13] Disorders such as hypothyroidism and hypoparathyroidism or thrombocytopenia (low platelet levels), and psychiatric illnesses are common late-occurring features.

[15] Studies provide various rates of 22q11.2DS in schizophrenia, ranging from 0.5 to 2.0% and averaging about 1.0%, compared with the overall estimated 0.025% risk of the 22q11.2DS in the general population.

[21] Individuals with DiGeorge syndrome also have a higher risk of developing early onset Parkinson's disease (PD).

[24][25][26] Hypernasality occurs when air escapes through the nose during the production of oral speech sounds, resulting in reduced intelligibility.

If the structure of the soft palate velum is such that it does not stop the flow of air from going up to the nasal cavity, it will cause hypernasal speech.

These errors include a limited phonemic (speech sound) inventory and the use of compensatory articulation strategies resulting in reduced intelligibility.

The phonemic inventory typically produced consists of sounds made in the front or back of the oral cavity such as: /p/, /w/, /m/, /n/, and glottal stops.

Compensatory articulation errors made by this population of children include: glottal stops, nasal substitutions, pharyngeal fricatives, linguapalatal sibilants, reduced pressure on consonant sounds, or a combination of these symptoms.

It is reasoned that a limited phonemic inventory and the use of compensatory articulation strategies is present due to the structural abnormalities of the palate.

The speech impairments exhibited by this population are more severe during the younger ages and show a trend of gradual improvement as the child matures.

[24][28] DiGeorge syndrome is caused by a heterozygous deletion of part of the long arm (q) of chromosome 22, region 1, band 1, sub-band 2 (22q11.2).

[31] Of the 30–50 genes in the deleted region, a number have been identified as possibly playing a role in the development of some of the signs and symptoms.

The neural crest forms many of the structures affected in DiGeorge syndrome, including the skull bones, mesenchyme of the face and palate, the outflow tract of the heart, and the thymus and parathyroid stroma.

[32] Research in mouse models has shown that deletion of Tbx1 leads to several defects similar to those seen in humans, mainly affecting development of the great arteries and the thymus.

[40] Transport and golgi organization 2 homolog (TANGO2) also known as chromosome 22 open reading frame 25 (C22orf25) is a protein that in humans is encoded by the TANGO2 gene.

[citation needed] Mutations in the TANGO2 gene may cause defects in mitochondrial β-oxidation[42] and increased endoplasmic reticulum stress and a reduction in Golgi volume density.

[43] These mutations results in early onset hypoglycemia, hyperammonemia, rhabdomyolysis, cardiac arrhythmias, and encephalopathy that later develops into cognitive impairment.

[22] Diagnosis of DiGeorge syndrome can be difficult due to the number of potential symptoms and the variation in phenotypes between individuals.

In these cases a diagnosis of 22q11.2DS is confirmed by observation of a deletion of part of the long arm (q) of chromosome 22, region 1, band 1, sub-band 2.

Genetic analysis is normally performed using fluorescence in situ hybridization (FISH), which is able to detect microdeletions that standard karyotyping (e.g. G-banding) miss.

[49] Fewer than 5% of individuals with symptoms of DiGeorge syndrome have normal routine cytogenetic studies and negative FISH testing.

[56][57] This estimate is based on major birth defects and may be an underestimate, because some individuals with the deletion have few symptoms and may not have been formally diagnosed.

[59] The signs and symptoms of DiGeorge syndrome are so varied that different groupings of its features were once regarded as separate conditions.

[63] This article incorporates public domain text from The U.S. National Library of Medicine peripheral: Purine nucleoside phosphorylase deficiency