Current molecular diagnostic tests identify a pathogenic TSC1 or TSC2 variant in nearly 90% of patients with a definite clinical diagnosis of TSC [12], and studies indicate that clinically diagnosed TSC patients with ‘no mutation identified’ (NMI) are most likely to carry either a somatic, mosaic mutation, or a deep intronic variant that affects splicing [13,14,15,16,17,18,19]. Here, TSC2 is linked to tuberous sclerosis.