Natural history of spinal muscular atrophy in children: an analysis of 117 cases.

Abstract

To study the natural history of spinal muscular atrophy (SMA) in Chongqing and surrounding areas, China, and to provide a clinical basis for comprehensive management and gene modification therapy for SMA. A retrospective analysis was performed on the medical data and survival status of 117 children with SMA. Of the 117 children, 62 (53.0%) had type 1 SMA, 45 (38.5%) had type 2 SMA, and 10 (8.5%) had type 3 SMA, with a median age of onset of 2 months, 10 months, and 15 months, respectively. Compared with the children with type 2 SMA or type 3 SMA, the children with type 1 SMA had significantly shorter time to onset, consultation, and confirmed diagnosis (P<0.05) and a significantly shorter diagnostic time window (age from disease onset to consultation) (P<0.05). Pneumonia as the initial symptom, weakness in head control, crying weakness, and eating difficulty were more commonly observed in children with type 1 SMA (P<0.05). Scoliosis and lower limb joint contracture were more common in children with type 2 SMA than in those with type 1 SMA (P<0.05). All 117 SMA children (100%) had homozygous deletion of the SMN1 gene, and the homozygous deletion of exon 7 was the most common type (68.4%, 80/117). The 6-year survival rate of children with type 1 SMA was only 10%±5%, which was significantly lower than that of children with type 2 or 3 SMA (P<0.05). Age of onset ≤3 months, pneumonia as the initial symptom and weakness in head control were the risk factors for death in children with type 1 SMA (P<0.05). The children with type 2 SMA had non-linear regression of motor ability. There are differences in clinical manifestations and survival rates among children with different types of SMA. The children with type 1 SMA have a low survival rate, and those with type 2 SMA may have non-linear regression of motor ability. Early identification and management of SMA should be performed in clinical practice.