Search

Background: Hypophosphatasia (HPP) is an inborn disease caused by pathogenic variants in ALPL. Low levels of alkaline phosphatase (ALP) are a biochemical hallmark of the disease. Scarce knowledge about the prevalence of HPP in Scandinavia exists, and the variable clinical presentations make diagnostics challenging. The aim of this study was to investigate the prevalence of ALPL variants as well as the clinical and biochemical features among adults with endocrinological diagnoses and persistent hypophosphatasaemia. Methods: A biochemical database containing ALP measurements of 26,121 individuals was reviewed to identify adults above 18 years of age with persistently low levels of ALP beneath range (≤ 35 ± 2.7 U/L). ALPL genetic testing, biochemical evaluations and assessment of clinical features by a systematic questionnaire among included patients, were performed. Results: Among 24 participants, thirteen subjects (54.2%) revealed a disease-causing variant in ALPL and reported mild clinical features of HPP, of which musculoskeletal pain was the most frequently reported (n = 9). The variant c. 571G > A; p.(Glu191Lys) was identified in six subjects, and an unreported missense variant (c.1019A > C; p.(His340Pro)) as well as a deletion of exon 2 were detected by genetic screening. Biochemical analyses showed no significant differences in ALP (p = 0.059), the bone specific alkaline phosphatase (BALP) (p = 0.056) and pyridoxal-5′-phosphate (PLP) (p = 0.085) between patients with an ALPL variant and negative genetic screening. Patients with a variant in ALPL had significantly higher PLP levels than healthy controls (p = 0.002). We observed normal ALP activity in some patients classified as mild HPP, and slightly increased levels of PLP in two subjects with normal genetic screening and four healthy controls. Among 51 patients with persistent hypophosphatasaemia, fifteen subjects (29.4%) received antiresorptive treatment. Two patients with unrecognized HPP were treated with bisphosphonates and did not show complications due to the treatment. Conclusions: Pathogenic variants in ALPL are common among patients with endocrinological diagnoses and low ALP. Regarding diagnostics, genetic testing is necessary to identify mild HPP due to fluctuating biochemical findings. Antiresorptive treatment is a frequent reason for hypophosphatasaemia and effects of these agents in adults with a variant in ALPL and osteoporosis remain unclear and require further studies.

Calcemia is not routinely determined among people living with human immunodeficiency virus (HIV). In people living with HIV, the most frequent electrolyte disturbance is hyponatremia and since symptoms of hypocalcemia often are unspecific, calcium is typically measured with some delay. Hypocalcemia in people living with HIV is mainly due to indirect causes such as vitamin D deficiency, renal failure, or drug related. However, in rare cases direct viral involvement of the parathyroid glands has been reported. We present a case of a 67-year-old male living with HIV who presented at an emergency department with symptomatic severe hypocalcemia, without any previous history of neck surgery, radiation therapy or large infections in the head and neck area. At the time of admission serum concentrations were for ionized calcium 0.98 mmol/L (ref. 1.18–1.32 mmol/L) and PTH 1.3 mmol/L (ref. 2.0–8.5 pmol/L). Vitamin D status was sufficient with 25OHD at 73 nmol/L to 112 nmol/L (ref. 60–160 nmol/L) from 2016 through 2019. The patient was diagnosed with primary hypoparathyroidism and was treated with Alphacalcidol 0,5 μg × 1/daily, calcium 500 mg × 4 the first day followed by 400 mg × 2 and magnesium 360 mg × 3, which induced rapid clinical recovery with dissolvement of muscular pain and biochemical improvement. This case study suggests that further studies are needed to investigate the added value of routine monitoring for hypocalcemia as part of clinical follow-up of people living with HIV.