Background/Purpose

Mild forms of adult hypophosphatasia may have subtle manifestations, and may go unrecognized. The aim of this study was to get a better knowledge of its clinical spectrum.

Methods

We performed a computerized search of low total alkaline phosphatase among laboratory records.  The diagnosis of hypophosphatasia was confirmed by measuring serum pyridoxal phosphate (PLP) and bone alkaline phosphatase. Carotid ultrasonography was performed in patients and controls with a MyLab 70 scanner (Esaote; Genoa, Italy), equipped with 7–12 MHz linear transducer.

Results

Over a 31 month period, we identified 130 individuals with at least one determination of serum alkaline phosphatase less than  26 u/l. After reviewing the clinical records, unexplained persistently low levels were found in 42 individuals who accepted to participate in the study (10 men, 32 women). Age range was 20-77 yr (mean 51). Total alkaline phosphatase levels were positively correlated with bone alkaline phosphatase (r=0.52, p<0.001). Serum PLP was inversely correlated with bone alkaline phosphatase. Ten individuals (24%) had PLP levels above the reference range of 175 nmol/l, consistent with hypophosphatasia. In comparison with those with normal PLP levels, these individuals had higher frequency of hypertension (50 vs 12%, p=0.02). Likewise, individuals with hypophosphatasia showed a trend to have early atherosclerotic disease. Carotid ultrasound showed bilateral plaques in 4 out of 9 patients (44%), and only in 26% of the age and sex-matched controls. The intima-media thickness also tended to be increased in the patients (670±70 vs. 648±110 microns; p=0.18).

Conclusion

These preliminary data suggest that individuals with adult hypophosphatasia may be at increased cardiovascular risk. The results should be confirmed in larger studies.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/is-adult-hypophosphatasia-a-cardiovascular-risk-factor/