BONE-MINERAL STATUS IN CHILDREN WITH PHENYLKETONURIA UNDER TREATMENT

Bone mineral status was assessed in 48 children with phenylketonuria ( PKU) (20 M, 28 F, aged 2.5-17 y). Bone density was measured in the dis tal third of the right forearm using single photon absorptiometry and was expressed as +/-SD with respect to age- and gender-matched control s. Serum calcium (Ca), magnesium (Mg), phosphorus (P), alkaline phosph atase (ALP), parathyroid hormone and 25-hydroxyvitamin D were measured in morning samples. The ratios of urinary Ca/creatinine (UCa/UCr), UP /UCr, UMg/UCr and hydroxyproline (OH-Pr)/UCr were calculated in urine samples collected over a period of 3 h. Patients' data were compared w ith those of 50 controls (22 M, 28 F, aged 3-15 y). The data showed se vere osteopenia (below -2 SD) in 22/48 patients. Bone loss was more pr ominent in patients over 8 y old. Bone density correlated significantl y with age (r = -0.56, p < 0.001) and with Phe (r = -0.49, p < 0.007) but did not correlate with the other biochemical indices studied. Comp aring PKU children with controls, significantly higher serum calcium a nd magnesium (p = 0.04, p < 0.001, respectively), lower ALP (p = 0.01) , higher UCa/UCr ratio (p < 0.001), lower UP/UCr (p < 0.001) and lower UOH-Pr/UCr (p < 0.001) were found. Dietary compliance was poor in pat ients over the age of 8 y, as only 3/22 of less than or equal to 8 y h ad mean serum phenylalanine >10 mg dl(-1), in contrast to 21/26 in the older group. It is clear from the data that osteopenia is commonly fo und in PKU patients fi om early Life. The biochemical data indicate a metabolic state of low bone turnover in PKU patients. In conclusion, a better, more restricted diet may correct osteopenia.