ESPE Abstracts

Background: Hypophosphatasia (HP) is a rare inherited disorder characterised by defective bone and teeth mineralization because of deficient serum and bone alkaline phosphatase activity due to mutations in the tissue-nonspecific ALP (TNALP) gene. Infantile HP (IHP) is one of the six recognized clinical forms according to age at presentation and clinical features. IHP is characterised by skeletal abnormalities due to demineralization and rachitic changes in the metaphyses, premature craniosynestosis, respiratory problems, and failure to thrive. Serum alkaline phosphatase (AP) activity is markedly reduced, which leads to increased serum/urine phosphoethanolamine (PEA), inorganic pyrophosphate (PPi), and pyridoxal-5’phosphate (PLP).

Objective and hypotheses: We report a 4.5-month-old female infant with the infantile form of HP. The patient was hospitalized due to failure to thrive, growth retardation, severe bone deformities, and hypotonia.

Method: The diagnosis was based on physical findings, haematological investigations, and radiographic skeletal features.

Results: The examinations revealed short stature and severe skeletal deformities: short and bowed limbs, an abnormally shaped chest, and an abnormal skull shape with soft skull bones. Radiographic diagnostic findings showed decreased ossification of the skull, generalized demineralization of the bone, defective metaphyseal modelling, and rachitic changes in the metaphyses. Laboratory investigations showed hypercalcemia (2.8 mmol/l), reduced serum alkaline phosphatase activity (33 U/l), and increased urine PEA (1855 mmol/l).

Conclusion: Infantile HP is a rare inherited disorder presented with severe bone deformities. The biochemical diagnosis is based on laboratory assays on markedly reduced serum AP, and increased urinary PEA.