Natural history of facial and skeletal features from neonatal period to adulthood in a 3M syndrome cohort with biallelic CUL7 or OBSL1 variants

3M syndrome is characterized by severe pre- and post-natal growth restriction, typical face, slender tubular bones, tall vertebral bodies, prominent heels and normal intelligence. It is caused by biallelic variants of CUL7, OBSL1 and, more rarely, CCDC8. The aim of this study is to evaluate facial and skeletal findings in 3M patients from neonatal period to adulthood. A total of 19 patients with a median age of diagnosis of 9.2 months were included in this study and were followed for two to 20 years. CUL7 and OBSL1 variants were found in 57.9% and 42.1% of patients, respectively, five of which are novel. Most of patients had triangular face, frontal bossing, short fleshy nose, full fleshy lower lip, transverse groove of rib cage, hyperlordosis and prominent heels. Three new early-diagnostic signs were observed in infants; two were infraorbital swelling of the lower lid and facial infantile hemangioma, both of which became less pronounced with aging. The third was the central tubercle of the upper lip that became more prominent with in time. While slender long bones did not change with aging, the tall vertebral bodies became more prominent radiologically. The mean birth length in patients was -4.3 SDS. Eight patients reached a mean final height of -4.9 SDS. Despite described growth hormone (GH) insensitivity in 3M syndrome, 12 patients either with GH deficiency or with normal GH levels were treated with GH; seven patients responded with an increase in height SDS. This study not only provided early diagnostic signs of the syndrome, but also presented important follow-up findings.