Haploinsufficiency of the ACAN gene has been reported in patients with (a) idiopathic, harmonious short stature but with advanced bone age, (b) disharmonic short stature with brachydactyly, craniofacial dysmorphia, or in children with intrauterine growth delay and an early installation of osteoarthritis [9,13,14]. The gene discussed is ACAN; the disease is osteoarthritis.