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

We report the case of a boy with partial skull defects in addition to widespread craniotabes due to vitamin D deficiency rickets. He was born at 30 wk and 4 d of gestation (birth weight, 2406 g). At 77 d of age, clinical examination of the head revealed widespread craniotabes of the occipital region centered around the lambda suture, and palpation revealed a defect of about 1 cm in the parietal bone of the left occipital region. Cranial computed tomography showed thinning of the cortex and bone defects in the parietal bones bilaterally, as well as in the left occipital bone. At 3 mo of age, he was diagnosed with vitamin D deficiency rickets and was administered alfacalcidol for 4 mo. Although patients with vitamin D deficiency rickets are prone to fractures, bone defects, as in this case, have not been reported. In addition to vitamin D deficiency rickets, the causes of the bone defects, in this case, are hypothesized to be abnormalities in the Ras-mitogen activated protein kinase pathway associated with Noonan syndrome, and long-term compression of the back of the head. However, there are no other similar reports, and further ones need to be accumulated.