Rhizomelic Chondrodysplasia Punctata Type 1

Rhizomelic Chondrodysplasia Punctata Type 1
	Gene:	PEX7; chr6q23.3

Syndrome Information
	Clinical Description:	Symptoms of Rhizomelic Chondroplasia Punctata type 1 (RCDP1) include proximal shortening of the limbs, cataracts, severe mental retardation, seizures, and calcific stippling of cartilage. About 50% of patients are clinically severe and do not survive beyond 5 years. RCDP1 is associated with deficient erythrocyte plasmalogens and elevated phytanic acid (phytanic acid is normal in the newborn period). Measurement of plasmalogen synthesis and phytanic acid oxidation can be used to distinguish RCDP1 from two single enzyme defects that are clinically indistinguishable from RCDP1. Copies of the patient's biochemical analysis are extremely helpful in result interpretation.
	Inheritance Pattern:	Autosomal Recessive
	Genotype-Phenotype Correlation:	None known

Test Information
	Test Method:	Bidirectional sequencing of exons 7 and 9 (plus intron-exon boundaries) of PEX7.
	Clinical Utility:	Identification of causative mutations in known or highly suspicious cases of RCDP1 based on clinical presentation and the blood biomarker profile; targeted carrier testing of relatives of proband; predictive prenatal testing when familial mutations are known.
	Clinical Sensitivity:	90% of patients will have at least one mutation identified by this test panel; approximately 57% will have both mutations identified.
	Analytic Sensitivity:	Greater than 97% for nucleotides analyzed. All reports will indicate if a certain percentage of nucleotides were not called or were analyzed in a single direction.
	Turn Around Time:	2-3 weeks
	Fee and CPT Codes:	$422 for routine testing on a blood 83891 x 1 83898 x 2 83904 x 4 83909 x 4 83912 x 1 Please contact the lab to arrange testing for known mutations on blood or prenatal samples.

Special Considerations
	We request that copies of the patient's biochemical analysis be submitted with the sample. Fewer than 5% of patients with an RCDP clinical phenotype and deficient plasmalogen synthesis may have a single enzyme defect in this pathway (RCDP2 & 3). Careful biochemical characterization can identify these patients in advance.

	INFORMED CONSENT from the patient is required prior to ordering a genetic test. The DNA Diagnostic Lab's consent is located on the second page of the requisition form. There is also a patient brochure, "Things Every Patient Should Know Before Consenting to a Genetic Test", available for download.
Helpful Links
	Sample Requirements Requisition and Billing forms Clinical information on RCDP1 Family friendly information on peroxisomal disorders: Global Foundation for Peroxisomal Disorders Patient and Family Page for general resources on genetic testing.