Publication:

Seizures and isolated motor delay in two siblings: looking beyond cerebral palsy

Rickets is a metabolic bone disorder resulting from impaired mineralization of the growing skeleton and may present with nonspecific features such as motor delay, muscle weakness, and seizures. In some children, particularly when skeletal manifestations are subtle, the underlying metabolic cause may be overlooked and the presentation may initially be attributed to nutritional deficiency or a primary neurological disorder. We report two siblings born to consanguineous parents who presented with delayed gross motor milestones and features of rickets. The elder child additionally had hypocalcemic seizures. Both children demonstrated hypocalcemia, markedly elevated alkaline phosphatase and parathyroid hormone levels, normal-to-elevated serum 25-hydroxyvitamin D concentrations, and without renal phosphate wasting. They failed to respond to conventional vitamin D supplementation. Genetic analysis revealed a homozygous pathogenic duplication in exon 8 of the CYP27B1 gene, confirming the diagnosis of VDDR-IA. Treatment with calcitriol and calcium led to rapid biochemical normalisation and significant clinical improvement, culminating in independent ambulation on follow-up. This report emphasizes the importance of considering vitamin D dependent rickets in children with early-onset rickets and poor response to standard therapy, particularly in the presence of consanguinity or sibling involvement. Early genetic diagnosis enables targeted treatment and prevents prolonged morbidity.