Achondroplasia is caused by a recurrent defect in the transmembrane domain of the FGFR3 gene that determines its activation.49 Clinical features include long-bone shortening, especially in the proximal region of the upper and lower extremities, resulting in a disproportionate short stature and macrocephaly with variable frontal and parietal bossing and mid-facial retrusion.50 The gene discussed is FGFR3; the disease is achondroplasia.