Abstract
Small for gestational age (SGA) refers to the size of an infant at birth, and is defined as a birth weight and/or birth length below the -2.0 SDS for the gestational age. In approximately 10% of cases, SGA is not compensated for in the postnatal period, with the pathogenesis of this condition being attributed to various monogenic syndromes or chromosomal abnormalities. The difficulty in making a pathogenetic diagnosis in this group of patients is due, on the one hand, to the similarity of phenotypic manifestations in the structure of the disease, on the other hand, to the variability of clinical manifestations within a specific syndrome. Conducting various molecular genetic studies is the main method of diagnosing the form of SGA. Microcephalic osteodysplastic primordial dwarfism type II (MOPD II) is one of the most common genetic variants of SGA, with its phenotypic features including skeletal anomalies and cerebrovascular changes. The disease is caused by biallelic mutations in PCNT gene. This study presents the clinical characteristics of the first patient with microcephalic osteodysplastic primordial dwarfism type II in the Russian Federation. The nucleotide changes detected in the patient have not been previously described in the world literature.