| Number (%) of families | |
| Small alterations | 78 (95) |
| Missense mutations | 55 (67) |
| Within exons 5–9 | 48 (59) |
| Outside exons 5–9 | 7 (9) |
| Other types | 23 (28) |
| Splicing mutations | 8 (10) |
| Non-sense mutations | 4 (5) |
| Frameshift deletions/insertions | 5 (6) |
| In frame deletions | 6 (7) |
| Genomic rearrangements | 4 (5) |