There is variability in the attainment of developmental milestones in the CDKL5 disorder.
Journal of Neurodevelopmental Disorders 2015, 7:2
This is an interesting article with the aim of investigating variation in attainment of developmental milestones and associations with underlying genotype in CDKL5 Disorder..
The study included 109 females and 18 males. By 5 years of age, only 75% of the females had attained independent sitting and 25% independent walking whilst a quarter of the males could sit independently by 1 year 3 months. Only one boy could walk independently. There is no surprise that girls fared better than the boys in this study, due to the condition being X-linked, however, it should be noted the sample size of males is small. Throughout the CDKL5 community parents and carers have noted that there is a great deal of variability in the milestones the children achieve. We have seen children with the same mutation that are affected very differently, therefore it is not surprising that the study found there were was also no clear correlation between mutation group and milestone, although those with late truncating mutations (nonsense) did attain the most milestones.
More recently in the UK and across the world children are being diagnosed much earlier than in previous years. Often before the age of one. Naturally receiving the diagnosis for most families is absolutely devastating, and the questions that run through their minds is "what will my child be able to do", "will they sit", "will they walk", from this article you can drawn the conclusion that there is no real way of knowing, unless your child is affected by a late truncating mutation.