A case of Noonan syndrome with skull defect due to vitamin D deficiency rickets

Area of Science:

• Pediatric Endocrinology
• Developmental Biology
• Medical Genetics

Background:

• Vitamin D deficiency rickets is a common condition in infants, typically associated with bone deformities and fractures.
• Skull abnormalities like craniotabes (softening of the skull) are known manifestations of rickets.
• However, significant skull bone defects are not commonly reported in association with this condition.

Observation:

• A premature infant born at 30 weeks gestation presented with widespread craniotabes and a palpable parietal bone defect at 77 days of age.
• Cranial CT scans revealed bilateral parietal bone defects and a left occipital bone defect, alongside cortical thinning.
• The infant was diagnosed with vitamin D deficiency rickets and treated with alfacalcidol.

Findings:

• This case highlights the unusual occurrence of partial skull defects in an infant with vitamin D deficiency rickets.
• The etiology of these bone defects is hypothesized to involve vitamin D deficiency rickets, potential Ras-mitogen activated protein kinase pathway abnormalities (possibly related to Noonan syndrome), and sustained external head compression.
• This represents a novel association, as such skull defects have not been previously documented in the context of rickets.

Implications:

• This case expands the known spectrum of skeletal manifestations of vitamin D deficiency rickets.
• It suggests that underlying genetic predispositions or external factors may contribute to severe cranial abnormalities in infants with rickets.
• Further research and case accumulation are needed to elucidate the precise mechanisms and confirm these associations.