The article describes the development of multifactorial pulmonary hypertension (PH) associated with hypoxemia on the basis of a long-term clinical observation of the child with type II mucosolipidosis (ML). The literature data on the etiology, pathogenesis, clinical symptoms, diagnostic methods, modern ML treatment are presented. Results of patients' examination in dynamics, disease course, prescribed therapy and response to it are described. The study substantiates the connection of PH development with hypoxemia and pulmonary hypoplasia, progression of multiple dysostosis, incl. facial dysmorphism and thoracic dysplasia in patients with ML. The algorithm for examining patients with ML should include monitoring of oxygen saturation and pressure in the pulmonary artery in order to timely diagnose and treat hypoxemia and PH. © 2019, Pediatria Ltd.. All rights reserved.