How common is this disorder

Diagnosis/testing.

Classic Cockayne syndrome (CS) is diagnosed by clinical findings including
postnatal growth failure and progressive neurologic dysfunction along with other
minor criteria; atypical cases may require molecular genetic testing.

The two genes responsible for Cockayne syndrome are ERCC6 (75% of individuals)
and ERCC8 (25% of individuals). Sequence analysis for both genes is clinically
available.

Cockayne syndrome is inherited in an autosomal recessive manner. The parents of
an affected child are both obligate carriers of an abnormal gene. Heterozygotes
are asymptomatic. Each Sib of a proband has a 25% chance of being affected, a
50% chance of being an asymptomatic carrier, and a 25% chance of being
unaffected and not a carrier.

Reproduction has not been reported in any individual with CS. Carrier detection
in at-risk family members is available on a clinical basis once the mutations
have been identified in the proband. Prenatal testing may be available through
laboratories offering custom prenatal testing.

You can read more on this disorder on the following attached site:
http://www.ncbi.nlm.nih.gov/books/bv.fcg...