22q11.2 deletion syndrome is a pattern of malformations resulting from abnormalities during cephalic neural crest migration and during the development of the third and fourth branchial arch. It is also known as DiGeorge syndrome, as it is most often associated with a de novo 3 Mb hemizygous 22q11.2 deletion. The recognition of similarities and phenotypic overlap between DiGeorge syndrome and other disorders associated with genetic defects in 22q11 has led to an expanded description of the phenotypic features of this syndrome. Indeed, the extent of this phenotypic variability can often make it difficult to accurately diagnose DiGeorge syndrome. Tertiary monosomy resulting from the 3:1 segregation of the respective chromosomal segments of the chromosomes involved in a balanced translocation in meiosis is rarely reported in the literature. In this report, we present a female infant with dysmorphic facial features, microcephaly, a cleft palate, unilateral membranous choanal atresia, convulsions, hypocalcemia, semilobar holoporencephaly and echocardiographic abnormalities. To the best of our knowledge, this is the first description of a newborn displaying both DiGeorge syndrome and deletion 18p syndromes.