Table 1

Patient characteristics

 Severe SMA
Type 0/1a*
Very severe phenotype (n=3)
Type 1b*
Classical phenotype (n=16)
Type 1c*
Prolonged survival (n=23)
Gender (F:M)1:29:710:13
Mean age at onset, months (range)0 (0)2.1 (0.8–5.0)4.8 (1.0–8.0)
Death (%)3 (100)14 (88)†4 (17)
Mean age at death, months (range)0.4 (0.1–0.5)8.6 (3.5–19)26.5 (14–39)
Respiratory support >16 hours/day, n (%)‡3 (100)1 (0)5 (20)
Mean age at start of respiratory support >16 hours/day, years (range)‡0 (0)0.9 (0.9)14.5 (1.8–38)
Median maximum age at follow-up (range)§NA5 months (2.5 months–12 years)7.4 years (15 months–52 years)
SMN2 copy number
 1300
 20151
 30021
 4001
Fasciculations of the tongue (%)1009394
Motor milestones
 Head control in prone position, n (%)0018 (81)
 Rolling, n (%)008 (23)
Mean age at acquiring milestone (months)
 Head controlNANA3.5
 RollingNANA5.2
History of feeding difficulties, n (%)3 (100)14 (88)17 (74)
Need of (non)-invasive ventilation at any time during the day3 (100)2 (12)10 (40)
Mean age at start of any (non)-invasive respiratory support, years (range)0 (0)0.8 (0.6–1.1)11 (1.3–36)
Cardiovascular abnormalities, n0
 Intermediate and mild SMA
Type 2a (n=49)Type 2b (n=38)Type 3a (n=33)Type 3b (n=33)Type 4 (n=5)
Gender (F:M)28:2125:1318:1515:184:1
Mean age at inclusion, years (range)16.2 (1.5–42.3)20 (2–66.7)31.5 (2.4–65.7)42.6 (42–77.5)51.2 (41.0–68.8)
Mean age at onset, months (range)9 (3.5–24)14.5 (6–30)20 (6–36)120 (42–294)444 (366–522)
Mean age at diagnosis, months (range)17 (4.0–54)44.8 (0.1–378)88.3 (1–294)222 (48–558)485 (372–558)
Mean disease duration, years (range)15.3 (0.3–40.4)18.6 (1.2–64.8)29.7 (1.2–62.2)32.8 (2.0–71.4)13.6 (7.5–24.2)
Death, n (%)2 (4)0 (0)1 (3)0 (0)0 (0)
Mean age at death, years (range)37.5 (28–47)66 (66)00
SMN2 copy number (n)
 100000
 211010
 3433215**40
 43415254
 500020
Fasciculations of the tongue, n (%)34 (76)21 (64)10 (32)6 (20)2 (40)
Polyminimyoclonus of the fingers, n (%)40 (89)33 (97)27 (87)28 (93)4 (80)
Distal hypermobility, n (%)††40 (100)27 (100)21 (84)15 (65)1 (33)
Respiratory support at night, n (%)‡15 (31)3 (8)6 (19)1 (3)0 (0)
Mean age at start of respiratory support at night, years (range)‡14 (2–38)19 (2–66)46 (15–61.5)40 (39.6)0 (0)
Respiratory support during daytime, n (%)‡3 (6)3 (5)2 (6)0 (0)0 (0)
Respiratory support >16 hours/day, n (%)‡2 (4)1 (2)2 (6)0 (0)0 (0)
Mean age at start of respiratory support >16 hours/day, years (range)‡20 (16–24)31 (31)34 (20–47)0 (0)0 (0)
Scoliosis surgery, n (%)30 (61)20 (54)9 (26)1 (4)0 (0)
Mean age at scoliosis surgery, years (range)8.6 (3.7–15.8)12.9 (7.3–31.8)25.1 (10.1–54.5)15.8 (15.8)0
Cardiovascular abnormalities, n¶00000
  • Head control: Lifting head from surface in prone position.

  • Rolling: To roll to one side from supine position.

  • *Classification according to Dubowitz et al4 and Mercuri et al2 (see online supplementary file).

  • †Fourteen children died and invasive respiratory support was started in one child at the age of 7 months.

  • ‡Including non-invasive and invasive support.

  • §Oldest age known at follow-up.

  • ¶Including tetralogy of Fallot and ventricular septum defect.

  • **One patient with heterozygous deletion of SMN1 and a point mutation in exon 4 (c.542A>G).

  • ††Hypermobility of the distal and proximal interphalangeal joints was a very common finding (88% of all patients) and was not confined to patients with severe SMA (penalised log regression p=0.001).

  • F, female; M, male; NA, not applicable; SMA, spinal muscular atrophy; SMN, survival motor neuron.