Bone Mineral Density in Patients with Phenylketonuria in Iran

Factors like low-protein diet may impose Phenylketonuria (PKU) patients to impaired skeletal disease. The present study assessed the status of Bone Mineral Density (BMD) among PKU patients on a low-protein diet.
A cross-sectional study was conducted (Tehran, Iran, 2019). Patients aged ≥ 4 years old with a definite diagnosis of PKU on a low-protein diet were included. BMD values of the lumbar spine and femoral neck were assessed. The primary objective was assessing femoral and lumbar BMD status in PKU patients.
Forty-one PKU patients entered the study. The mean BMI was 20.712±4.833 Kg/m2. The mean bone age was significantly lower than chronological age (10.9 vs. 12.4 years; P=0.008). The results showed a bone mass reduction in 23.1% of all patients.  A significant correlation was observed between lumbar and femoral BMD values (P=0.001; r=0.516). Most patients (about 77%) had lumbar Z-scores>-1 and 10.3% showed Z-scores in the range of osteoporosis. Age (P=0.004) and age at diagnosis (P=0.002) were the influencing factors on BMD status. The results showed a significantly inverse correlation between BMD lumbar levels with the patient’s chronological age (P=0.016), age of PKU diagnosis (P=0.002), and phenylalanine level (P=0.025)
The results delineated impaired skeletal status among PKU patients on a low-protein diet. Lumbar Z-score values inversely correlated with the patient’s chronological age, age at PKU diagnosis, and phenylalanine level. Hence, early PKU diagnosis and treatment during neonatal period, as well as controlling phenylalanine concentration may improve BMD status.