Bone mineral status in children with phenylketonuria under treatment

Abstract

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 distal third of the right forearm using single photon absorptiometry and was expressed as ±SD with respect to age‐ and gender‐matched controls. Serum calcium (Ca), magnesium (Mg), phosphorus (P), alkaline phosphatase (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 3h. Patients' data were compared with those of 50 controls (22M, 28F, aged 3‐15y). The data showed severe osteopenia (below ‐2 SD) in 22/48 patients. Bone loss was more prominent in patients over 8y old. Bone density correlated significantly 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. Comparing PKU children with controls, significantly higher serum calcium and 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 patients over the age of 8y, as only 3/22 of ≤ 8y had mean serum phenylalanine >10mgdl−1, in contrast to 21/26 in the older group. It is clear from the data that osteopenia is commonly found in PKU patients from 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.

Peak bone mass in patients with phenylketonuria

“…Several studies have suggested an increased risk of fractures (Greeves et al 1997) or a defect in bone mineralization in adults, adolescents, and children with PKU (Allen et al 1994;Al-Qadreh et al 1998;Barat et al 2002;Carson et al 1990;Hillman et al 1996;McMurry et al 1992;Perez-Duenas et al 2002;Schwahn et al 1998;Zeman et al 1999). However, most previous studies assessing bone quality in PKU (Allen et al 1994;Al-Qadreh et al 1998;Carson et al 1990;McMurry et al 1992;Schwahn et al 1998) did not evaluate bone mineral density (BMD) by the gold-standard method of DXA (Genant et al 1999), reported heterogeneous patient populations (Barat et al 2002;Perez-Duenas et al 2002;Schwahn et al 1998), or comprised only a small number of patients (Barat et al 2002;Schwahn et al 1998).…”

“…However, most previous studies assessing bone quality in PKU (Allen et al 1994;Al-Qadreh et al 1998;Carson et al 1990;McMurry et al 1992;Schwahn et al 1998) did not evaluate bone mineral density (BMD) by the gold-standard method of DXA (Genant et al 1999), reported heterogeneous patient populations (Barat et al 2002;Perez-Duenas et al 2002;Schwahn et al 1998), or comprised only a small number of patients (Barat et al 2002;Schwahn et al 1998).…”

Nutritional issues in treating phenylketonuria

“…Progressive reduction in bone density is a well-known complication of PKU (Al-Qadreh et al 1998;Porta et al 2008;Schwahn et al 1998). The pathogenesis of this common feature, however, remains unclear.…”

Metabolismo do cálcio na fenilcetonúria

“…Ao avaliar o estado mineral ósseo de 48 crianças com fenilcetonúria tratadas, e comparando-as com crianças normais, Al-Qadreh et al 43 verificaram que a presença de osteopenia foi significativamente maior no grupo das crianças portadoras da doença. Quando esses pacientes foram divididos por idade (maiores e menores de 8 anos), pôde-se observar menor densidade óssea naqueles mais velhos, os quais também apresentavam os maiores níveis de fenilalanina.…”