Background. Hypophosphatasia (HPP) is a hereditary disorder belonging to the group of mineral metabolism disturbances, caused by deficiency of tissue-nonspecific alkaline phosphatase due to pathogenic and likely pathogenic variants in the ALPL gene. It is characterized by a wide spectrum of clinical manifestations, ranging from severe perinatal phenotypes to milder forms presenting in childhood and adulthood. Early loss of primary teeth, and later of permanent teeth, is often the first symptom of HPP but remains underestimated. HPP is not always recognized by physicians, especially in mild cases. The importance of radiological diagnostics in identifying all forms of HPP should be emphasized. Currently, with the availability of effective pathogenetic therapy, early diagnosis is of particular importance, as it allows the disease to be identified before life-threatening conditions develop. Case series. This article presents a case series of both severe HPP with manifestation at birth and milder forms involving dental and skeletal system involvement. Enzyme replacement therapy stabilized the condition of a patient with the severe perinatal form, as well as two patients with the childhood form of HPP, in whom early loss of primary teeth was the first clinical sign of the disease. Of particular interest is the description of a familial case involving the patient’s mother, who had clinical manifestations of HPP in early childhood, but the diagnosis was only established during the evaluation of her son.

Conclusion. Effective pathogenetic therapy has been developed for HPP, which improves the health status of patients. Early diagnosis and timely initiation of treatment will help preserve health and, in severe cases, save patients’ lives.