Deep intronic mutations leading to pseudoexon inclusion have been documented in multiple diseases with increasing frequency: in patients with neurofibromatosis (Cunha et al., 2016), Duchenne muscular dystrophy (Trabelsi et al., 2014), HPRT deficiency (Corrigan, Arenas, Escuredo, Fairbanks, & Marinaki, 2011), as well as several hereditary tumor syndromes, like melanoma (Harland, Mistry, Bishop, & Bishop, 2001), retinoblastoma (Dehainault et al., 2007), and breast cancer (Anczukow et al., 2012). The gene discussed is HPRT1; the disease is hyperinsulinemic hypoglycemia, familial, 4.