Two Cases of Frontal Variation of Idiopathic Calvarial Thinning—Therapeutic Effect of Denosumab and Romosozumab

Idiopathic calvarial thinning is a rare condition that causes progressive, painless thinning of the skull bones without systemic disease. We present 2 cases of idiopathic calvarial thinning involving the bifrontal region. Both patients exhibited forehead depression and had normal biochemical tests except for mild vitamin D deficiency. The first patient received treatment with denosumab for 3 years, showing no further progression of the skull thinning. The second patient was treated with denosumab for 3 years, followed by romosozumab for 1 year, resulting in no further progression and even slight recovery of the skull thickness. These cases demonstrate that idiopathic calvarial thinning can involve the bifrontal region and highlight the favorable treatment and prognosis with denosumab or romosozumab.