Table 2.
Slow-channel congenital myasthenic syndrome kindred and acetylcholine receptor mutations.
| Mutation/Domain | DB1 | Onset/Activity2 | Medical Exam3 | Grade4 | MEPP amplitude5 | MEPC decay6 | EpM7 | αBT8 | References |
|---|---|---|---|---|---|---|---|---|---|
| αG153S N-terminal | 1 | Infant-53/sports | Ocular, hand, arm | 1–2 | 36–90% | 7.8/26.4 | Yes | Low | (20, 37) |
| αV156M N-terminal | - | 14 | No ocular; neck, jaw, limb | 1 | NA | NA | NA | NA | (37) |
| αN217K M1 | 9, 10 | 8–57 | Ocular, hand, arm, neck, gait | 2 | 43–69% | 3.6/22.1 | Yes | Low | (21, 69) |
| αV249F M2 | - | Infant/wc 8 | Severe generalized | 3 | 44% | 2.4/43.9 | Yes | 39% | (19) |
| αT254I M2 | - | 16 | No ocular; neck, arm | 1 | NA | NA | NA | NA | (37) |
| αS269I M2 | - | 23 | Arm, jaw, legs | 1 | Normal | 20/28* | NA | 44% | (37) |
| αC418W M4 | - | Infant-teens | Ocular, arm, legs | 2 | NA | NA | NA | NA | (42) |
| βV229F M1 | 7 | 18–50 | Hand, neck, arms | 1 | 20% 0.67 | 2.25/26.1 | Yes (ps) | NA | (41, 69) |
| βL262M M2 | 4 | inf/wc 13 | Severe generalized, atrophy | 3 | 19% | 38.6* | Yes | High | (36) |
| βV266M M2 | 13 | Infant | Ocular, face, limb | 2–4 | 43–69% | 3.5/35.6 | Yes | Low | (21, 69) |
| δS268F M2 | 6 | Infant/wc teens | No atrophy, severe generalized | 4 | 50% | 31* | Yes (ps) | NA | (39, 69) |
| εL78P N-terminal | 22–29 | Ocular, face, neck, shoulder, hand, hip | 1 | NA | NA | NA | NA | (40) | |
| εL221F M1 | - | 17–40s | Ocular, wrist, hand, neck | 1 | NA | NA | NA | NA | (40) |
| εT264P M2 | - | Infant/wc teens | Severe limb, neck | 3 | Reduced | 1.5/16.5 | Yes | 39% | (18) |
| εL269F M2 | 2, 5 | Infant | Severe focal, resp insuf. | 3 | 36–69% | 3.3/50 | Yes | NA | (21, 52, 55) |
Kindred/Proband number in the SCS database
Age or range of age of onset within kindred./Level of activity or disability. wc = wheelchair.
Most prominent features of weakness.
Score defined as 1: onset after infancy, limb, ocular weakness minimal limitation of activity; 2: onset in infancy, limitation of activity; 3: respiratory insufficiency, confinement to wheelchair; 4: death from respiratory failure.
Amplitude of miniature endplate currents or miniature endplate potentials. Shown is percent of control. NA=not available.
Time constant(s) of decay of miniature endplate current or potentials in milliseconds (ms). Normal = 2–3.3 ms.
MEPP.
noise analysis.
EpM=endplate myopathy confirmed. yes=present; n=absent. ps= presynaptic-predominant endplate myopathy.
α-Bungarotoxin binding sites on endplates. Shown is percent of control, reduced or increased.