CONTEXT: Familial tall stature (FTS) is considered to be a benign variant of growth with a presumed polygenic etiology. However, monogenic disorders with possible associated pathological features could also be hidden under the FTS phenotype. OBJECTIVE: To elucidate the genetic etiology in families with FTS and to describe their phenotype in detail. METHODS: Children with FTS (the life-maximum height in both the child and his/her taller parent > 2 SD for age and sex) referred to the Endocrinology center of Motol University Hospital were enrolled into the study. Their DNA was examined cytogenetically and via a next-generation sequencing panel of 786 genes associated with growth. The genetic results were evaluated by the American College of Molecular Genetics and Genomics guidelines. All of the participants underwent standard endocrinological examination followed by specialized anthropometric evaluation. RESULTS: In total, 34 children (19 girls) with FTS were enrolled in the study. Their median height and their taller parent's height were 3.1 SD and 2.5 SD, respectively. The genetic cause of FTS was elucidated in 11/34 (32.4%) children (47,XXX and 47,XYY karyotypes, SHOX duplication, and causative variants in NSD1 [in 2], SUZ12 [in 2], FGFR3, CHD8, GPC3, and PPP2R5D genes). Ten children had absent syndromic signs and 24 had dysmorphic features. CONCLUSION: Monogenic (and cytogenetic) etiology of FTS can be found among children with FTS. Genetic examination should be considered in all children with FTS regardless of the presence of dysmorphic features.

Department of Pediatrics 2nd Faculty of Medicine Charles University Prague and University Hospital Motol Prague 5 150 06 Czech Republic

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