Sclerosing bone disorders encompass a range of genetic and acquired diseases. The potential for bone metastases is often a significant concern, especially when multiple discrete lesions are present. Several non-malignant disorders can also produce similar patterns of bone abnormalities. Among these is osteomesopyknosis, a rare condition characterized by multiple sclerotic lesions in the axial skeleton. Only a few cases of this presumably genetic disease have been documented. In this report, we present a new case and review previously published cases to enhance understanding and facilitate recognition of this disorder within the broader category of sclerosing bone diseases.

Bone tissue homeostasis relies on the coordinated activity of the bone-forming osteoblasts and bone-resorbing osteoclasts. Osteomesopyknosis is considered a distinctive rare sclerosing skeletal disorder of unelucidated pathophysiology and presumably autosomal dominant transmission. However, the causal genes are unknown. We present a case report encompassing clinical assessments, imaging studies, and whole-exome sequencing analysis, complemented by functional in vitro experiments. This new case of osteomesopyknosis was associated with a missense ALOX5 variant predicted to induce protein misfolding and proteasomal degradation. Transfection experiments demonstrated that the variant was associated with reduced protein levels restored by proteasomal inhibition with bortezomib. Likewise, gene expression analysis showed that the mutated gene was associated with a decreased RANKL/OPG ratio, which is a critical driver of osteoclast precursor differentiation. Our data indicate impaired bone resorption as the underlying mechanism of this rare osteosclerosis, implicating ALOX5 pathogenic variants as potential etiological factors.

The clavicle is a long bone that forms the anterior border of the thoracic inlet. Anatomic abnormalities of the clavicle can lead to compression of the innominate artery and trachea due to mass effect. These anatomic abnormalities can be amenable to surgical resection, which can provide complete resolution of symptoms. We present a case of tracheal compression by the innominate artery in an adult man, caused by a clavicular abnormality due to an underlying bone mineralization disorder, corrected by partial resection of the right clavicle. The patient underwent successful open surgical resection of his right clavicular head leading to resolution of his tracheal compression by the innominate artery. We believe that this is the first description of tracheal compression due to osteomesopyknosis. This case demonstrates that compression of the innominate artery due to a clavicular abnormality can be safely corrected via open surgical resection.

We report two cases of an axial osteosclerosis with histopathologic findings of osteomesopyknosis in siblings. Osteomesopyknosis is a benign hereditary osteosclerosis that can show a radiologic pattern similar to blastic metastatic disease. The aim of this article is to inform radiologists about the existence of this benign condition and its various radiologic manifestations. Therefore, we discuss the principal differential diagnosis and point out the key imaging findings of osteomesopyknosis in order to avoid overdiagnosis in future cases.

Osteomesopyknosis is a rare sclerosing bone disorder of autosomal dominant inheritance. We report a first case of osteomesopyknosis in Korea. A 16-year old girl complained of diffuse back pain for 1 year. We performed physical examination, biochemical investigations and imaging studies. A radiograph of spine revealed rugger-jersey vertebra and sandwich vertebra. Bone specific alkaline phosphatase, osteocalcin and C-terminal telopeptides of type I collagen were normal. Only an axial skeleton involvement was shown on the whole body bone scan. This patient was diagnosed to have osteomesopyknosis. Osteomesopyknosis is characterized by normal level of bone turnover marker and an axial bone involvement. Osteomesopyknosis can be occurred in Korea and needs to be considered when patients, especially young patients, suffer from back pain and have only axial osteosclerosis.