Early Signs of Puberty in children with CDKL5
It’s a fact that in the general population children are starting puberty earlier but for children with CDKL5 and similar conditions often enter puberty earlier, known as precocious puberty.
The Medical Literature and Patterns of Puberty in Children with Neurodevelopmental disabilities
The literature on early signs of puberty is quite limited.  An early article from 1999 looked at 32 children with various neurodevelopmental disabilities, including cerebral palsy, mental retardation, and other conditions, who showed some signs of puberty.1   This study determined that roughly half of the children experienced central precocious puberty directly caused by their neurological disorders, while the remainder simply had early thelarche (breast development) or pubarche (pubic hair growth) that was of no medical significance.  This study suggests that children with neurodevelopmental disorders are up to 20 times more likely to enter puberty early as compared to typically developing children, particularly if they are girls.
Should Children be Evaluated?

The simple answer is yes, any signs of puberty before age nine should be evaluated.  If your child just has isolated pubic hair growth or isolated breast development, your clinician might run a few simple blood tests to determine whether you need a referral to an endocrinologist.  He or she may also order an X-ray to evaluate your child’s bone age.  In most cases, this is as far as the evaluation needs to progress, and the child simply needs to be watched for further signs of puberty.
If your child has multiple signs of puberty very early on, it is probably best to have a basic endocrinology tests.  This is particularly true if your child is a boy, since boys are more likely to have peripheral causes for early puberty, such as a tumor.  This evaluation will attempt to determine the cause of the early puberty, which in most cases will end up as a diagnosis of central (neurologically-based) precocious puberty after excluding any other causes.  It is important to get evaluated because it is possible that there may be a secondary cause for the early puberty signs.  In addition, treatment is available for children who wish to have it and can benefit from it.
Any child with early signs of puberty should be closely monitored for other signs that may signify that additional evaluation is needed.
Is this a Problem?
Traditionally, isolated early pubic hair development (premature pubarche), which is consistently the most common early sign of puberty in children, has been described as a benign condition with little medical relevance.  It is thought to be caused by early activation of the adrenal glands, and is often called premature adrenarche.  It may be accompanied by body odor, acne, and sometimes underarm hair.  Isolated early breast development (premature thelarche), especially before age two, is also thought to be a benign condition with little medical relevance.
However recent studies are questioning this fact.  Multiple studies have linked early puberty, in the general population as well as children with complex medical needs and particularly premature adrenarche in girls, with polycystic ovary syndrome or metabolic syndromes related to obesity.  Moreover, a small study used to illustrate the lack of knowledge in this area demonstrated that girls with premature adrenarche also had elevated levels of cortisol, and a large percentage had psychological disorders and lower IQs.5  While these studies may or may not be relevant to children with CDKL5, they do demonstrate that a supposedly benign condition may not actually be benign.  Much further research is needed in this area to determine if treatment or intervention should be initiated for some or all of these children.
Should this be Treated?
At this time, children with isolated pubic hair growth (with or without body odor) or isolated breast development are not typically treated.  Children who have multiple signs of puberty may be treated to slow down the progression of development.  This may be important to some children who are self-conscious about the early development of their bodies and to help children reach their full adult height while optimizing their bone age.
Treatment also depends on the age of the child.  If a child begins puberty at age two or three, her final adult height may be severely limited by the early puberty.  For this child, treatment is likely to be important.  But if another child begins developing at age seven or eight, his final adult height may only be moderately impacted, making treatment a tougher decision.
Some families, especially those with children who have more severe motor impairments, may choose not to treat their children.  For these families, the slight reduction in height that occurs naturally with somewhat early puberty may be an asset as their children age and grow.  Lifting, transferring, and transporting the child may be easier at a slightly smaller size.  Smaller, lighter children are also less likely to lose motor function or develop as severe orthopedic problems as compared to larger, heavier children. In no way are we advocating intentionally making a child smaller, but when it occurs naturally, choosing not to interfere with nature may be the right choice for some families.
This decision must be made with input from the child, family, and the child’s doctor.  It is a decision that will be different for every family.
Next steps?
Despite the fact that signs of early puberty are exceptionally common in children with neurodevelopmental  and similar disorders, little information exists to guide parents and doctors on evaluation and treatment.  This is a subject that demands greater evaluation by medical researchers.  Children who have experienced early signs of puberty need to be studied over decades as they age to determine if early puberty has any negative ramifications on their health and development.  Guidelines need to be put in place to maximize growth and development.
Most importantly, parents need to be given expectations as to whether this common but not necessarily normal progression of puberty in children with CDKL5 is OK.
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