ESPE Abstracts

Introduction: Hypophosphatasia (HPP) is a rare autosomal recessive or dominant genetic disorder characterized by the abnormal development of bones and teeth and deficiency of tissue non-specific alkaline phosphatase activity. These abnormalities occur due to defective mineralization, the process by which bones and teeth take up minerals such as calcium and phosphorus. The specific symptoms can vary greatly from one person to another, sometimes even among members of the same family.

Case: A 6 year old boy visited the clinic because of short stature, intermittent bone pain and mild developmental delay. He was born at 36 weeks via vaginal delivery, weighed 3.02 kg, and had hypoglycemia history after birth. The patient was the 1st child among 3 children of non-consanguineous parents with above average height. He was 105.6 cm (<3th percentile) in height, 17.4 kg (3rd percentile) in weight. He had high arched palate and large ears. Blood chemistry findings were as follows: total calcium 10.3 mg/dL (Reference range, RR, 8.3–10.0); phosphorous 5.3 mg/dL (RR, 2.5–4.5); alkaline phosphatase (ALP) 341 IU/L (RR, 104–338 in adult). Serum electrolytes, glucose, blood gases, hepatic and renal function tests, as well as routine urinalysis were normal. The growth hormone stimulation test showed normal response. Next-generation sequencing (NGS) was carried out, we identified heterozygous variant, including a truncating variant (p.Leu276Ter) in the ALPL gene. The mother of the patient were confirmed to have same variant with bone pain and relatively low ALP level. We could not find bone hypomineralization and flared metaphysis in skeletal X-ray, like former case reports of childhood type of hypophosphatasia.

Conclusion: We report a novel mutation of ALPL presenting with short stature and bone pain. We should consider mild hypophosphatasia in a patient with short stature and relatively low ALP level, and attempt to find genotype and phenotype correlation.