3M syndrome: A Tunisian seven-cases series

3M syndrome (3MS) is a rare autosomal recessive primordial growth disorder characterized by a severe pre- and post-natal growth deficiency, minor dysmorphisms and skeletal abnormalities, contrasting with normal intellect and endocrine function. Three different genes have been so far involved in the disease, with mutations in CUL7, OBSL1 and CCDC8. The CUL7 gene mutations are accountable for 77,5% of the genetically confirmed patients, with a founder mutation identified in exon 24 for the Maghreb families. The follow up is mainly orthopedic with possible GH-based treatment. The objective of this report was to carry out a clinical analysis of a series of Tunisian patients with features evoking 3MS and to perform a molecular analysis of the CLU7 exon 24. We carried out a descriptive retrospective study including Tunisian patients who consulted at the congenital disorders and hereditary diseases department of Charles Nicolle's hospital, Tunis, Tunisia, for intra-uterine onset growth retardation with normal intellect. We selected the patients having characteristic 3MS facial dysmorphia. The molecular analysis of the CUL7 exon 24 was performed using PCR and Sanger sequencing searching the founder mutation c.4451_4452delTG. Seven patients were included in this study. Consanguinity was noted for four families. The mean age at the first consult was 2.5 years. All the patients had an intra-uterine onset growth retardation with a preserved head circumference. All patients presented facial dysmorphia of 3MS, with a prominent forehead (7/7), a triangular face (6/7), an underdeveloped midface (7/7), a fleshy tipped nose (5/7), anteverted nares (6/7), a long philtrum (7/7) and full lips (4/7). All the patients presented skeletal abnormalities with various severities such as lumbar lordosis, hyperextensible joints, short thorax, square shoulders, hip dislocation, and prominent heels. Less frequent features were noted such as spina bifida occulta in one case, and single transverse palmar crease in 4 cases. One GH treatment response was reported. The molecular genetic analysis of the CUL7 gene (exon 24) revealed the founder mutation for all the patients which reinforces the hypothesis of founder effect for 3MS in the Tunisian population.