This is because the 22q11 region has a structure that makes it highly prone to rearrangements during sperm or egg formation.The exact mechanism that causes all of the associated features of the syndrome is unknown. 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. TBX1
Haploinsufficiency of the TBX1 gene (T-box transcription factor TBX1) is thought to be the cause of some of the symptoms observed. Point mutations in this gene have also been observed in individuals with DiGeorge syndrome. TBX1 is part of the T-box family of genes which have an important role in tissue and organ formation during embryonic development and it may have a role in the regulation of differentiation of post migration neural crest cells. 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. When there is a loss of expression of FGF18 during the development of the pharyngeal arches, neural crest cell death is seen. Although neither FGF18 or TBX1 are expressed in the neural crest cells, TBX1 might have a role in the regulation of FGF18 expression, ensuring that the differentiation of these cells in the pharyngeal region is correct.
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. This phenomenon is referred as velopharyngeal inadequacy (VPI). Hearing loss can also contribute to increased hypernasality because children with hearing impairments can have difficulty self monitoring their oral speech output. The treatment options available for VPI include prosthesis and surgery.Difficulties acquiring vocabulary and formulating spoken language (expressive language deficits) at the onset of language development are also part of the speech and language profile associated with the 22q11.2 deletion. Vocabulary acquisition is often severely delayed for preschool-age children. In some recent studies, children had a severely limited vocabulary or were still not verbal at 2–3 years of age. School-age children do make progress with expressive language as they mature, but many continue to have delays and demonstrate difficulty when presented with language tasks such as verbally recalling narratives and producing longer and more complex sentences. Receptive language, which is the ability to comprehend, retain, or process spoken language, can also be impaired, although not usually with the same severity as expressive language impairments.Articulation errors are commonly present in children with DiGeorge syndrome. 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.