Familial Hypercholesterolemia
Gene: LDLR
Protein: low density lipoprotein receptor
Gene: PCSK9
Protein: proprotein convertase, subtilisin/kexin-type 9
Gene: APOB
Protein: apolipoprotein B
Clinical Characteristics
- Hypercholesterolemia, usually present from birth
- Heterozygous:
- Total cholesterol of 250-450 mg/dl
- LDL-cholesterol of 200-400 mg/dl
- Homozygous:
- Total cholesterol greater than 500 mg/dl
- LDL-cholesterol greater than 450 mg/dl
- Heterozygous:
- Corneal arcus
- Xanthomas, around eyelids, on tendons and between fingers
- Increased risk of coronary heart disease (CHD) at an early age
- Heterozygous: CHD in 40’s or 50’s if untreated
- Homozygous: severe CHD often fatal before age 20 if untreated
Inheritance pattern: Autosomal co-dominant
What Can Be Learned From This Test
Testing is performed by a tiered approach.
Tier 1 includes sequencing exons 1-4, 9-11, and 17 of LDLR, exon 7 of PCSK9, and the portion of exon 26 in APOB containing common pathogenic variants.
Tier 2 includes sequencing the remaining exons of LDLR and PCSK9, an additional fragment of exon 26 of APOB containing other published pathogenic variants, and deletion/ duplication testing of select exons of LDLR and PCSK9.
The sequencing tests will detect point mutations, small deletions, and small insertions. The deletion/ duplication tests may not detect a partial copy number variant, but will detect a whole gene deletion or duplication. Large deletions and duplications in LDLR have been reported.
Sample Requirements
Draw 2ml–4ml of blood in EDTA/purple-top tube (minimum of 1ml–2ml for infants).
Turnaround time: 10-14 business days per tier
CPT Codes and Cost
Tier 1
- Codes: 81401, 81406, 81479Ìý
- Cost: $370
Tier 2
- Codes: 81401, 81405, 81406, 81479 x3Ìý
- Cost: $1,050
Both Tiers
- Codes: 81401, 81405, 81406 x2, 81479Ìý
- Cost: $1,420
Known Variant Testing
- Code: 81479Ìý
- Cost: $225
Additional Information
Ìý