Multisuture craniosynostosis and acquired Chiari malformation secondary to vitamin D deficiency rickets: illustrative case.

backgroundWhile frequently sporadic or genetic in etiology, craniosynostosis may occur secondarily due to underlying defects in bone mineralization. X-linked hypophosphatemia represents a common genetic cause of rickets, with sequelae including craniosynostosis and Chiari malformation type I (CM-I). In contrast, severe nutritional vitamin D deficiency-induced rickets represents a rare cause of acquired or postnatal craniosynostosis and CM-I, with few cases reported in the published literature. OBSERVATIONS: The authors present the case of a 2-year-old boy with a history of severe vitamin D deficiency rickets who presented with multisuture craniosynostosis, acquired CM-I, and clinical symptoms and signs of increased intracranial pressure (ICP). His headaches and papilledema resolved with cranial vault expansion and bone-only posterior fossa decompression. By the time of his presentation with craniosynostosis, his vitamin D deficiency had been treated and resolved for about 1 year. LESSONS: Secondary or postnatal craniosynostosis often does not present with characteristic head shape changes but may be associated with elevated ICP and acquired CM-I, which may require surgical intervention. Late presentation or diagnosis of craniosynostosis in young children without typical features should prompt investigation for underlying disorders of bone metabolism. https://thejns.org/doi/10.3171/CASE26200.