CDD is caused by pathogenic variants in the gene<unk> . This gene provides instructions for making a protein (cyclin-dependent kinase-like 5) that is essential for normal brain development and function. The<unk>  protein is widely expressed in the brain, predominantly in nerve cells (neurons), with roles in cell proliferation, neuronal migration, axonal outgrowth, dendritic morphogenesis, and synapse development. Inheritance Pattern: the<unk>  gene is located on the X chromosome but nearly all known pathogenic mutations are de novo, rather than being inherited from an affected mother or father; the profound neurodevelopmental disabilities of CDD patients makes it extremely unlikely they would have children. There is one reported case of an inherited<unk>  mutation; a mother carried a<unk>  mutation on one X chromosome, but was high functioning and showed only mild cognitive impairment. The mother’s mutant<unk>  allele was skewed in its X-inactivation, being expressed in only 20% of circulating lymphoblasts. However, her daughter, who was diagnosed with CDD, expressed the mutant in 50% of her circulating lymphoblasts. Females: a mutation in one of the two copies of the<unk>  gene in each cell causes the<unk> . Males: a mutation in the only copy of the gene causes the<unk> .
CDKL5 deficiency disorder
NGLY1 deficiency
LRBA deficiency
ATR-16 syndrome
ZC4H2 deficiency
HUPRA syndrome
PGM3 deficiency
ATR-X syndrome