Cerebral Cavernous Malformations (CCM)
PrintCerebral cavernous malformations (CCM) are vascular malformations, mostly located within the central nervous system. The prevalence in the general population is estimated at 0.1 – 0.5%1,2. This condition is characterized by abnormally enlarged capillary cavities without intervening brain parenchyma and approximately 50 – 75% of CCM patients have symptoms, which can include chronic headaches, seizures and hemorrhagic strokes1,4.
Cavernous angiomas can be sporadic or familial with autosomal dominant inheritance3,5. Familial CCM occurs in 1:2,000 – 1:10,000 individuals and is associated with germline mutations in one of at least three genes, KRIT1, CCM2, and PDCD104,6. A mutation in one of these genes is responsible for approximately 80% of familial CCM, which represents ~50% of CCM cases in Hispanic-Americans and ~10 – 40 % in other populations5. The clinical detection rate for familial CCM mutation screening, using both gene sequence and gross gene deletion analysis, is 43% – 56% for KRIT1, 13 – 38% for CCM2, and 6% – 10% for PDCD107.
KRIT1 (Krev interaction trapped-1) also known as CCM1, is located on chromosome 7q11 and is comprised of 16 exons. The majority of mutations in KRIT1 are nonsense or frameshift mutations which results in premature protein translation termination. KRIT1 mutations account for most of the familial forms of CCM (43% – 56%). A founder mutation in KRIT1; c. 1363C>T is responsible for a large proportion of CCM cases in patients of Hispanic-American or Mexican descent8.
CCM2, previously known as MGC4607, is located on chromosome 7p13 and has 10 exons encoding the malcavernin protein, which contains a phosphotyrosine-binding domain. CCM2 mutations are observed in 13 – 38% of CCM patients, with 22% resulting from large genomic deletions in CCM2 gene9.
PDCD10 (Programmed Cell Death 10), also known as CCM3, is located on chromosome 3q26.1, and is comprised of 7 exons. PDCD10 patients exhibit a higher symptomatic percentage before 15 years of age, and are more susceptible to developing early onset cerebral hemorrhages compared to patients carrying a mutation in either the CCM2 or KRIT1 genes10. Recent studies have shown a 6% – 10% PDCD10 mutation detection rate in familial CCM, which is lower than the previously reported detection rate of ~40%, and suggests the possibility of a fourth CCM locus near PDCD107,10
Identification of mutations associated with cerebral cavernous malformations can aid early detection of cerebral cavernous malformations, as well as provide management and/or prevention of chronic headaches, seizures and hemorrhagic strokes.
CCM is a gene sequence analysis performed by PCR-based double-stranded automated sequencing in the sense and antisense directions for: KRIT1 (exons 4 – 16), CCM2 (exons 1 – 10) and PDCD10 (exons 2 – 8) plus at least 20 bases into the 5’ and 3’ ends of all introns. If no mutation is detected, analysis for gross deletions/duplications of the KRIT1, CCM2, and PDCD10 gene(s) is performed by the Multiplex Ligation-Dependent Probe Amplification (MLPA) kit, developed by MRC Holland. Specific mutation analysis for individual mutations known to be in the family is also available.
Familial CCM mutation screening, which includes both sequence and deletion analyses, has shown a clinical detection rate of 43% – 56% for KRIT1, 13 – 38% for CCM2, and 6% – 10% for PDCD107. The Cerebral Cavernous Malformations test is designed and validated to detect >99% of described mutations (analytical detection rate) in the KRIT1, CCM2 and PDCD10 genes.
Blood: Collect 3 – 5 cc from adult or 2 cc minimum from child in EDTA purple-top tubes (first choice) or yellow-top ACD tubes (second choice). Store at room temperature or refrigerate. Ship at room temperature.
Saliva: Collect 2 ml into OrageneTM DNA Self-Collection container. Store and ship at room temperature.
DNA: Send 20 μg in TE at 50 – 100 ng/μl. Store frozen and ship on ice or dry ice.
| Test Code | Technique | CPT Codes |
|---|---|---|
| 5320 | CCM2 Gene Sequence Analysis | 83891x1, 83894x11, 83898x10, 83904x20, 83909x20, 83912x1 |
| 5324 | CCM2 Deletion / Duplication | 83891x1, 83894x1, 83900x1, 83901x10, 83909x1, 83912x1 |
| 5340 | KRIT1 Gene Sequence Analysis | 83891x1, 83894x16, 83898x15, 83904x30, 83909x30, 83912x1 |
| 5344 | KRIT1 Deletion / Duplication | 83891x1, 83894x1, 83900x1, 83901x17, 83909x1, 83912x1 |
| 5360 | PDCD10 Gene Sequence Analysis | 83891x1, 83894x7, 83898x6, 83904x12, 83909x12, 83912x1 |
| 5364 | PDCD10 Deletion / Duplication | 83891x1, 83894x1, 83900x1, 83901x8, 83909x1, 83912x1 |
| 5368 | Comprehensive CCM: Step 1 KRIT1 Gene Sequence, Step 2 CCM2, PDCD10 Sequence and Deletion / Duplication for All 3 Genes (Reflex) |
83891x1, 83894x35, 83898x31, 83900x1, 83901x39, 83904x62, 83909x63, 83912x4 |
| 5370 | Comprehensive CCM: Step 1 KRIT1 Gene Sequence, Step 2 CCM2, PDCD10 Sequence and Deletion / Duplication for All 3 Genes (Concurrent) |
83891x1, 83894x35, 83898x31, 83900x1, 83901x39, 83904x62, 83909x63, 83912x4 |
| 5366 | KRIT1, CCM2, PDCD10 Deletion / Duplication | 83891x1, 83894x1, 83900x1, 83901x39, 83909x1, 83912x1 |
| Technique | Days |
|---|---|
| CCM2 Gene Sequence Analysis | 10-21 |
| CCM2 Deletion / Duplication | 7-14 |
| KRIT1 Gene Sequence Analysis | 10-21 |
| KRIT1 Deletion / Duplication | 7-21 |
| PDCD10 Gene Sequence Analysis | 10-21 |
| PDCD10 Deletion / Duplication | 7-14 |
| Comprehensive CCM: Step 1 KRIT1 Gene Sequence, Step 2 CCM2, PDCD10 Sequence and Deletion / Duplication for All 3 Genes (Reflex) |
10-42 |
| Comprehensive CCM: Step 1 KRIT1 Gene Sequence, Step 2 CCM2, PDCD10 Sequence and Deletion / Duplication for All 3 Genes (Concurrent) |
10-21 |
| KRIT1, CCM2, PDCD10 Deletion / Duplication | 7-14 |
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9. Liquori C et al. Am J Hum Genet. 2007;80(1):69 – 75
10. Denier C et al. Ann Neurol. 2006;60(5):550 – 6