Surfactant Deficiency: ABCA3

Non-Classic Cystic Fibrosis-Like Phenotype
	Gene:	SCNN1B; chr16p12.1

Syndrome Information
	Clinical Description:	This phenotype resembles non-classic cystic fibrosis (CF), but is actually a mild variant of pseudohypoaldosteronism (PHA). Findings include elevated sweat chloride concentration, chronic cough, and frequent lower respiratory infections. These patients do not have the more severe symptoms of either CF (severe lung disease, pancreatic insufficiency, infertility) or PHA (salt-wasting, volume depletion).
	Inheritance Pattern:	Autosomal Recessive
	Genotype-Phenotype Correlation:	This phenotype is caused by mutations in SCNN1B that reduce, but not destroy, protein production or function.

Test Information
	Test Method:	Bidirectional sequencing of the coding regions and intron-exon boundaries of SCNN1B
	Clinical Utility:	Identification of causative mutations in known or highly suspicious cases of mild PHA; rule-out alternate causes of CF-like symptoms when CFTR testing is negative; targeted carrier testing of relatives of proband; predictive prenatal testing when familial mutations are known.
	Clinical Sensitivity:	Sheridan et al (2005, Hum Molec Genet 14:3493) identified SCNN1B mutations in 2 of 20 patients (10%) with non-classic CF without CFTR mutations. Our test panel has been designed to detect >99% of mutations published to date.
	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:	Approximately 5 weeks
	Fee and CPT Codes:	$1342 for routine testing on a blood or DNA sample 83891 x 1; 83898 x 12; 83904 x 24; 83909 x 24; 83912 x 1 Please contact the lab to arrange testing for known mutations on blood or prenatal samples.

Special Considerations
	Several patients with CF-like symptoms have been described with one CFTR mutation and one SCNN1A/B/G mutation.

	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 ABCA3 and Surfactant Deficiency Link to the General Test Information page for a discussion of the uses and limitations of genetic testing Patient and Family Page for general resources on genetic testing.