Kugelberg-Welander syndrome (SMA3, autosomal dominant childhood-onset proximal spinal muscular atrophy, spinal muscular atrophy type III) is caused by defect in the SMN1 gene but this is complicated by there being multiple SMN2 copies in human genome and some very complex interactions.
- Onset after 18 months
- Patient is able to walk and death is usually in adult life
- Clinical presentation very variable, with typical motor neuron paralysis evolving and scoliosis as if variable penetrance. See spinal muscular atrophy.