Familial expansile osteolysis: a morphological, histomorphometric and serological study

Area of Science:

• Bone biology
• Cellular pathology
• Viral inclusions

Background:

• Familial expansile osteolysis (FEO) is a rare bone disorder.
• Osteoclasts are multinucleated cells responsible for bone resorption.
• Previous studies suggested a viral etiology for Paget's disease based on similar inclusions.

Purpose of the Study:

• To investigate the presence and characteristics of viral-like microcylindrical inclusions in osteoclasts from patients with FEO.
• To compare bone remodelling in FEO lesions with other osteoclast-related disorders.
• To determine if these inclusions are specific to Paget's disease.

Main Methods:

• Light and electron microscopy of bone biopsies from FEO patients.
• Quantitative histomorphometry to assess bone remodelling parameters.
• Serological testing for viral antibodies.

Main Results:

• Multinuclear osteoclasts with intranuclear viral-like microcylindrical inclusions were observed in FEO bone.
• Increased bone remodelling, high cell densities, and reduced reversal periods were noted.
• Lesions showed woven bone, fibrovascular tissue, and adipocytes, with bone replaced by adipose tissue in advanced stages.
• No significant differences in viral antibody titers were found between patients and controls.

Conclusions:

• Intranuclear viral-like microcylindrical inclusions in osteoclasts are not specific to Paget's disease.
• These inclusions are present in other disorders of osteoclast function, such as FEO, pycnodysostosis, osteopetrosis, and giant cell tumors.
• The findings suggest a broader role for these inclusions in osteoclast dysfunction rather than a specific viral link to Paget's disease.