Objective of the Paper: to describe a clinical case of paediatric hypophosphatasia (HPP) and identify clinical signs, most characteristic of the paediatric HPP form. Key Points. HPP is an congenital rickets-like disease caused by reduced activity of tissue-nonspecific alkaline phosphatase (ALP). According to the time of manifestation, there are perinatal, infant, paediatric, and adult HPPs. The article describes a clinical case of paediatric HPP in a 3.5-year old boy. HPP was diagnosed due to reduced ALP and characteristic X-ray findings. The diagnosis was confirmed with DNA testing: compound heterozygous mutation in с.571 G>A/с.144_148dup of ALPL was found. Conclusion. Typical findings in paediatric HPP are growth retardation and muscular hypotonia, motor retardation; gait disturbances, myalgia, marked fatigue causing limited period of walking; rachitic deformations, premature loss of milk teeth with unchanged roots, respiratory disturbances, and frequent bronchopulmonary disorders. Keywords: hypophosphatasia, children, alkaline phosphatase.