(VCFS) - A syndrome characterized by abnormal pharyngeal arch development that results in defective development of the parathyroid glands, thymus, and conotruncal region of the heart. The phenotype is highly variable, with no single clinical feature present in every patient. Affected individuals may present with structural or functional palatal abnormalities, cardiac defects, unique facial characteristics, hypernasal speech, hypotonia, and defective thymic development associated with impaired immune function. In addition, affected individuals may present with learning disabilities, overt developmental delay, and psychiatric disorders.