A Parent Friendly Description of RCDP.


A “Friendly” RCDP definition

This is a parent friendly explanation of RCDP written by Mary Ellis, mom to Ian Ellis and co-founder of
Rhizokids International.
What is RCDP?
Now that the doctors have scared you to death about RCDP, let me tell you the basics. It’s actually not a death sentence like they portray. Don’t get me wrong. You don’t have a healthy baby, but you do have a wonderful child that is going to love you and provide you with great joy as a parent. Ok, with that being said let’s get down to the basics about RCDP.
Rhizomelic Chondrodysplasia Punctata
The official scientific description is as follows : RCDP is an autosomal recessive form of chondrodysplasia punctata characterized by defective plasmalogen biosynthesis and impaired peroxisomes. Patients have shortened proximal limbs and severely disturbed endochondrial bone formation. You are probably thinking “Ok, so what does that mean?” At least that’s what I thought when my son
was diagnosed. I have tried to define these highlighted words to better help you understand the definition of RCDP.
What is autosomal recessive?
This is a mutation or change carried on an autosome (a chromosome not involved in sex determination) that is deleterious (hurtful or destructive) only in homozygotes (nucleus, cell, or organism with identical alleles of one or more specific genes.) This basically means that both the mother and the father have to have the defective gene in order for their baby to be born with RCDP. That means it is not anyone’s fault that their baby has RCDP. You could not have done anything to cause this or anything to prevent this. This gene has been in many previous generations in your family.
What does Rhizomelic mean?
Rhizomelic is the proximal shortening at the end of the bone closest to the trunk.That means the humerus and femur are shorter than they are supposed to be.
What is chondrodysplasia punctata?
A heterogeneous group of hereditary bone dysplasias, the common characteristic of which is stippling of the epiphyses in infancy.
• Stippling‐spotty calcium deposits
• Epiphyses‐ the end of a long bone that grows
This means that on an x‐ray your infants bones will look spotted at the ends.
What is a plasmalogen?
A plasmalogen is an ether lipid with an ether‐linked alkene(double bond next to the link) also known as a vinyl ether at the first carbon position of the glycerol. The second carbon has a typical ester‐linked fatty acid, and the third carbon usually has a phospholipid head group like choline or ethanolamine.
I am sorry about this definition. It is very complicated I know. The most important thing for you to understand is that children with RCDP have low levels of plasmalogens. The child’s plasmalogen level is how the doctors determine the prognosis for the children. The higher their plasmalogen level the less affected the child will be. The lower their plasmalogen level the more affected the child will be. RCDP kids are categorized into three categories based on their plasmalogen levels. Mild, Intermediate and Severe. It’s important to remember that their severity has nothing to do with the type of RCDP that they have but rather how high or low their plasmalogen levels are.
What is biosynthesis?
Biosynthesis is the building up of a chemical compound in the physiologic processes of a living
organism.
What are peroxisomes?
A peroxisome is a cell organelle containing enzymes such as catalose and oxidase, that catalyze the
production and breakdown of hydrogen peroxide.
I think this is the start of your understanding of Rhizomelic Chondrodysplasia Punctata. You probably feel like you have just earned a doctorate. I sure do!!! Now, let’s talk about the characteristics of RCDP.
Characteristics of RCDP
• Shortening of the humerus and femur
• Coronal clefts of the vertebral bodies
• Cataracts
• Lower than normal birth weight, length, and head circumference
• A growth deficiency
• Mental deficiency
• Seizures
• Calcium deposits at the joints
• Stiff, painful joints (this is not true for every child)
• Recurrent respiratory tract infections
• Aspiration
• Some children with RCDP have heart complications as well (this is not necessarily related to RCDP)
• Some children with RCDP also have hearing loss (this is not necessarily related to RCDP)
What are the different types of RCDP?
RCDP type 1 is the type that most of the research is on. This is the most prominent of the types. The children with type 1 have two defects. They have a low plasmalogen level and they also have a low phytanic acid oxidation. This means they can’t break down fatty acids. These children need to be on diet low in phytanic acid. This means nothing from a masticating animal ie Beef, Lamb, Venison or Dairy products.
RCDP type 2 and 3 only has one defect. They have low plasmalogen. Unlike type 1 their phytanic acid oxidation is normal. You are probably thinking type 2 and type 3 aren’t as severe as type 1. That is not necessarily the case. The determining factor in the severity of the case is the child’s plasmalogen level. Remember, if they have a very low level of plasmalogens their case is considered more severe than a child with a higher level of plasmalogens.
Occurrence of RCDP
• RCDP occurs 1 out of every 100,000 live births.
*This does not account for miscarriages that happen or abortions. This is per live births. There are also children that may not be diagnosed correctly and they actually have RCDP.
*There is a 25% chance, at conception, of a proband inheriting both mutant alleles and being affected with RCDP.
*There is a 50% chance, at conception, of a proband inheriting one mutant allele and being an unaffected carrier. That would be the case for the mom and dad.
*There is a 25% chance, at conception, of a proband inheriting both normal alleles and being a perfectly healthy baby.
Diagnosis of RCDP
Your child will have blood work sent to a lab and their plasmalogen levels are how the doctors diagnose RCDP. A child with extremely low plasmalogen levels has RCDP. Next, they will use a skin biopsy to determine the type of RCDP your child has.
Management of RCDP
There are many things you can do to help a child with RCDP. Physical therapy is recommended to improve contractures and orthopedic procedures may improve function in some children. Some children visit GI doctors to help with feeding or stomach issues. Some children also see an eye doctor for cataracts and have the cataracts removed. The children with hearing problems see an Ear, Nose, and
Throat Doctor (ENT) to help with hearing testing, hearing aids, and occasionally tubes being put in the ears. There are many things you can do to help your child. I have found the best thing for me is to talk to other parents with children with RCDP. They know the most about these kids and they have the best tips about how to care for these children.
Prognosis for RCDP
This is the worst part about RCDP. The prognosis for many of these children is not good. However, your child is unique and may outlive all expectations of the doctors. I am going to inform you what the doctors say about the children’s prognosis. I want you to remember though that your child is different from any other child with RCDP and know that there are several children that have been diagnosed with RCDP that are predicted to have a long life . According to a study by the Kennedy Krieger Institute 60% of children survived the first year, 39% the second year, and a few survived beyond age 10. The research shows that the majority of children do not survive beyond the first decade of life and a proportion of children die in the neonatal period. I do understand how devastating this prognosis is. I want you to remember though that this is not true for everyone. Your child could live to be 20 years old. If you expect great things then you just might receive great things.
Stay positive!