Hypertrophic osteoarthropathy (HO), formerly and incorrectly referred to as hypertrophic pulmonary osteoarthropathy, has primary and secondary forms. The primary form (pachydermoperiostosis) is often familial and is more commonly seen in males.
The secondary form can be seen in a variety of pulmonary and hepatic conditions, including:
- Lung cancer
- Carcinomas of liver and gut
- Inflammatory bowel disease
- Liver cirrhosis
- Congenital cyanotic heart disease
- Pulmonary fibrosis
- Graves disease
Patients can present with clubbing of fingers, periostosis of distal long bones, thickening of skin over face and ankles, gynecomastia, and arthritis and synovitis. The synovitis is accompanied by a viscous, non-inflammatory effusion.
Various etiologies have been proposed, but the most recent thought is that it is due to arteriovenous shunting (e.g., in the liver, lung, or various tumors). The idea is that unfragmented megakaryocytes get delivered to distal sites in systemic circulation instead of being filtered in the lungs. This leads to production of growth factors (PDGF and VEGF), which lead to angiogenesis, endothelial hyperplasia. In certain lung tumors, there is de novo production of these growth factors by tumor, which makes it to the peripheral circulation.
A neurogenic role has also been proposed. This is supported by the fact that pain and deformity resolve with peripheral vagotomy in both primary and secondary forms, even with the primary tumor intact.
Differential diagnosis for Multifocal Periostitis in Adults and children were covered earlier.