Calvarial melorheostosis: extremely rare case and diagnostic challenge

Melorheostosis is a rare bone disease that presents as sclerotic lesions growing on existing bone surfaces. This disease is of unknown etiology and affects both genders equally. The disease is unique in appearance, described in the literature as having a radiologic appearance of flowing candle wax, and usually occurs in the appendicular skeleton.

A 55-year-old male with a past medical history of hypertension, hyperlipidemia, insulin-dependent diabetes, right eye vision loss, and peptic ulcer disease presented to the emergency department complaining of headache and swelling on the left side of his head. The patient stated that the swelling had been present for 20–30 years. He denied any symptoms of dizziness, headache, diaphoresis, or chest pain. He was noted to have a palpable protrusion associated with the area of swelling and the patient stated that it was not associated dimension, anteroposteriorly. A separate smaller pedunculated lesion was noted at the left planum sphenoidale, measuring 1.4 cm. The angiogram portion of this exam showed that all arteries were clear of stenosis or occlusion except for the cavernous portions of the right internal carotid artery, which had some atherosclerotic calcifications, but no evidence of significant stenosis (not shown). CT angiogram showed no evidence of arterial impingement by the mass. Notably, the mass did not extend to the groove for the middle meningeal artery.

The radiologic differential diagnosis included osteoma, and the presence of the secondary lesion in the sphenoid raised concerns for Gardner syndrome. Metabolic bone disease as well as other hyperostotic syndromes such as Van Buchem’s disease were considered given the location; however, melorheostosis was favoured due to the appearance of the lesion on the CT scans, as well as the lack of interval growth when compared to an MRI scan obtained 8 years prior.

The patient underwent a left frontoparietal craniectomy for the resection of the calvarial lesion, a left orbitotomy for decompression of the orbital roof and resection of the smaller secondary lesion in the region of the anterior sphenoid, and a single-stage cranioplasty using a custom PEEK (polyetheretherketone) patient-specific 3D-printed custom cranial implant.

Pathologic examination of the primary mass showed a lesion grossly composed of dense sclerotic bone with growth along the outer and inner table of the calvarium. Histologic examination showed variable findings ranging from dense, sclerotic, lamellar bone, and areas of disorganized bone growth with several Haversian canals oriented perpendicularly to the appositional bone and fatty marrow in the intervening trabecular spaces with absence of a significant osteoblastic/osteoclastic component.

The author commented – “The diagnosis of melorheostosis is often suggested due to the radiologic recognition of the flowing candle wax appearance as described in the literature. However, there exist cases of melorheostosis that do not fit this profile, and careful radiologic and pathologic analysis can be essential in making this diagnosis.”

Further reading:

Calvarial melorheostosis: an extremely rare case and diagnostic challenge Gregory Wenokor et al Skeletal Radiology https://doi.org/10.1007/s00256-025-04882-w