[…] by leg muscle weakness that is most severe in the thigh muscles (quadriceps).
[icdlist.com]
She manifested the characteristic clinical features, including early-onset respiratory failure due to diaphragmatic paralysis and severe distal muscle weakness.
[ncbi.nlm.nih.gov]
Symptoms seem to appear in reverse order to that of SMA Type 1, with respiratory problems coming first, followed by severe muscle weakness, especially in the lower limbs.
[actsma.co.uk]