Table 2 Children with severe MSN_I and an identified rare disease (n = 459)
Rare disease groupN (%)
Neurological diseases110 (24.1)
    Syndromes34
    CNS structural anomalies76
Syndromes with dysmorphy or malformation and intellectual impairment56 (12.2)
    With chromosomal abnormality24
    Without chromosomal abnormality32
Severe congenital or genetic vision loss52 (11.3)
Skeletal diseases50 (10.9)
    Generalised9
    Focalised41
Severe congenital or genetic deafness45 (9.8)
Neuromuscular diseases41 (8.9)
Hereditary metabolic diseases27 (5.9)
Tumours24 (5.2)
Embryofetopathies19 (4.1)
Other rare diseases35 (7.6)
    Systemic disease5
    Dermatological disease6
    Haematological disease1
    Immunodeficiency1
    Collagen and extracellular matrix disease2
    Others20
Total459 (100)
  • CNS, central nervous system.