IMPE Abstracts

To describe the BMD at FH of well-controlled PKU patients we retrieved retrospectively, data from 18 compliant moderate/severe patients (7 female), under conventional treatment since diagnosis. Eleven had received sapropterin dihydrochloride (BH₄) since puberty, increasing their phenylalanine intake. FH, mid-parental height (MPH), genotype, fractures, and tolerance to phenylalanine intake (tol) before and after BH₄ were considered. Total Body (TB) and Lumbar Spine (LS) BMD were assessed by dual energy-ray absorptiometry (DEXA) lunar at prepubertal stage or Tanner stage2 (T1), puberty (T2), and postpuberty when FH was attained (T3). In 11 patients (3 females) Femoral BMD was available at a median age of 21.8 years (19-24). Male/female differences and BMD related to BH4 treatment were evaluated.

Results: FH was normal: -0.1±1.1 SDS with MPH of 0.67±0.7 (p: 0.02) confirming previous observations. Sixteen patients were compound heterozygous for PAH mutations and 2 siblings shared the same genotype. No fractures occurred in the studied period. The phenotype was moderate/severe: (tol) 360mg/day (230-500mg/day) at T1. Those patients treated with BH4 achieved a (tol) of 1800mg/day (700-3300mg/day). BMD (median (range) results are shown below. TB and LS, BMD were always normal without differences between boys and girls. Available Femoral BMD was normal too (0.4(-1.3 to 2.7 SDS). Only 1 patient presented at T1 BMD <2SDS. Patients without BH4 had significant worst BMD at prepuberty and achieved significantly lower BMD at FH than those treated.

Conclusions: With normal FH, our PKU cohort had always normal TB and LS BMD. Adequate nutrition allowed them to attain a normal peak bone mass. Patients treated with BH₄ achieved better BMD, probably related to more natural protein intake. Nevertheless, the negative influence of a more severe genotype in those untreated (not respondents to BH₄) cannot be excluded.