Endocrine Abstracts

JOINT3616

Objectives: Alkaline phosphatase (ALP) consists of a group of isoenzymes found in many body tissues including the liver, bone, kidney, placenta, and intestine. ALP levels change with age and are measured at the highest level with increased growth. Elevated serum ALP levels are a marker of some pathological conditions, and the approach to increased serum ALP levels is better determined. In contrast, information about the approach to patients with low ALP levels is more limited. We aimed to evaluate the etiological distribution of patients with persistently low ALP levels and the demographic and clinical characteristics of infants and children diagnosed with hypophosphatasia (HPP).

Methods: This retrospective study included 0-18 years of children having low ALP levels between September 2019 and July 2024. Patients were divided into permanent and transient low ALP levels. Patients diagnosed with HPP were further examined.

Results: 1825 patients with low ALP levels according to age and gender were identified. Of these patients, 79 patients were between 0-1 age (1 patient permanent, 78 patient transient) 1320 patients were between 1-11 ages (48 patient permanent, 1272 patients transient), 352 patients were between 11-13 ages (16 patient permanent, 336 patient transient), 74 patients were between 13-18 ages (15 patient permanent, 59 patient transient). 10 (0.54%) patients had a diagnosis of HPP. In the permanent subgroup without a diagnosis of HPP, calorie depletion (anorexia, malnutrition) was most frequent. Six of the children diagnosed with HPP were female and four were male. Two patients were investigated for short stature; one patient for hypercalcemia, hypercalciuria, epilepsy, and neuromotor developmental delay; one patient for respiratory distress and hypotonia; a patient was diagnosed while being followed up and treated with acute myeloid leukemia, one patient was diagnosed during a routine check-up, and one patient was diagnosed while his sibling was diagnosed. Seven different variants were detected in 9 families, all previously reported variants. Two of the variants were homozygous and five were heterozygous.

Conclusions: In our study involving a pediatric patient group, a wide range of disorders associated with low ALP activity were examined. In the case of persistent low ALP and additional specific symptoms, HPP should always be considered as a differential diagnosis. HPP presents differently in different age groups. While severe forms in young children are better known, unawareness or misinterpretation of symptoms in milder forms may lead to a delay in the diagnosis of milder cases in childhood or adolescence.