MLPA assay for the molecular diagnosis of SMA is based on a kit containing several probes for the SMA critical region, including specific probes for SMN1 and SMN2 genes, probes able to hybridize both genes and other probes for sequences mapped either within the SMA critical region (NAIP, GTF2H2, N-cadherin-like, CDH6 and RAD17 genes) or on other autosomal regions. Here, SMN1 is linked to proximal spinal muscular atrophy.