# Handbook of Genetic Counseling/Chondrodysplasia Punctata

Chondrodysplasia Punctata (X-linked Dominant - Conradi-Hunermann)

## Introduction

* Assess concerns and ask what they hope to gain from the session
* Discuss reason for follow-up
* Provide overview of session
** Interim medical/developmental history
** Discussion of concerns/questions
** Dr. will come in and do physical exam
** Discussion about follow-up plans

## Elicit interim medical history

* Any illnesses/hospitalizations/surgeries since last visit in
* Current medications-are there any?
* Any recent medical tests or procedures?
* Immunizations up to date?
* Review of systems

## Psychosocial update?

* Any changes in work?
* Any changes with who is around at home?
* How are things around the home generally?

## Genetic etiology

* Several forms of chondrodysplasia punctata known-about 25% of these are of the X-linked dominant type
* Incidence figures are difficult to determine because it is very rare
* ____'s is likely due to a new mutation, although there is some chance one of the parent's has gonadal mosaicism
* Recurrence risk for parents to have another child with _____'s condition is probably less than 2% (probably MUCH less, but in case of gonadal mosaicism, we should say this number)
* Risk for _____to have a child with her condition: 33% affected female, 33% unaffected female, 33% unaffected male (affected males usually die from condition in utero)

## Molecular genetics

* Exact gene associated with this condition is unknown
* People with this condition have been found to have mutations in Δ8-Δ7 sterol isomerase, an enzyme involved in the biochemical pathway leading to the synthesis of cholesterol
* People with this condition typically have elevated levels of 8(9) cholestanol, a product in the pathway of cholesterol synthesis

## Testing options

* Testing serum 8(9) cholestanol levels is a highly sensitive way of detecting people with the sterol isomerase mutation
* Clinical and research testing is available for both the serum 8(9) cholestanol level analysis and mutation analysis at several sites throughout the country
* There are research trials underway to understand the spectrum of mutations in the sterol isomerase gene

## Support groups

* MUMS: National Parent to Parent Network
    Julie J. Gordon
    150 Custer Court
    Green Bay, Wisconsin 54301-1243
    1-877-336-5333 (Parents only please)
    920-336-5333
    1-920-339-0995 (fax)
    E-mail: mums@netnet.net
    [Web: http://www.netnet.net/mums]
    This is a great organization. Can hook up parents of children with a particular condition with a family that has a child with that same condition. There are 4 people registered on this network with this condition. This can be helpful if the parents really want to know what to expect. This will not be so helpful if they are paired with a family whose child has had a much better or much worse time with the condition. It could give false hope, or more likely could make the family feel more afraid of what is to come. Should only be offered to parents who really seem to have a lot of questions about what to expect in the future.

## Resources

* Smith's Recognizable Patterns of Human Malformation
* OMIM-entry # 302960

## Notes

The information in this outline was last updated in 2003.