Vitamin D deficiency in Serbian patients with Rett syndrome

Rett syndrome (RTT) is a severe neurodevelopmental disorder. Bone manifestations of RTT include osteopenia and fractures. Studies addressing serum vitamin D levels in patients with RTT are scarce.

The goals of this study were (1) to determine the prevalence of vitamin D deficiency in patients with RTT, (2) to compare serum vitamin D levels between patients with RTT and those with other neurological diseases, and (3) to explore the correlation between demographic and clinical characteristics of patients with RTT and vitamin D levels.

Demographic and clinical characteristics included age, body mass index Z-score, mutation status, clinical severity score, presence of epilepsy, number of antiepileptic drugs, history of fractures, scoliosis, and ambulation ability. Laboratory parameters included serum 25-hydroxyvitamin D [25(OH)D], PTH, calcium, and alkaline phosphatase.

The study included 35 patients with RTT and 35 age-matched females with other neurological diseases. The median serum 25(OH)D concentration in the RTT group was 26.25 nmol/L, with values <75 nmol/L in all participants. Severe deficiency (<25 nmol/L) was detected in 17 of 35 (48.6%) patients. The median 25(OH)D concentration was significantly lower in patients with RTT than in control subjects. The risk for fracture by 12 years of age in patients with RTT was 35.3%. An inverse correlation of the 25(OH)D level to age and PTH level was detected. Patients receiving antiepileptic polytherapy had a 3.3 times greater chance for severe vitamin D deficiency than patients receiving monotherapy.

The prevalence of vitamin D deficiency in patients with RTT is higher than that in patients with other neurological diseases. The high risk for vitamin D deficiency should be accounted for in the strategy of antiepileptic treatment in RTT, especially when polytherapy is considered.