These include intellectual disability due to ACTB haploinsufficiency23, Becker’s Nevus syndrome due to low-grade mosaic ACTB hotspot mutations24, BWCFF resulting from constitutive missense mutations in exons 2–419–21, and a single case where moderate intellectual disability, white blood cell anomalies and thrombocytopenia are linked to a missense mutation in exon 625. The gene discussed is ACTB; the disease is Becker nevus syndrome.