Hopefully, you saw the cavitary lesion in the lower lobe of the left lung. Cavitary lesions can be due to infection, tumor, infarction, trauma, and other entities. In this case, it was infection.
Hypertrophic osteoarthropathy (HOA) was first described in 1868, and represents a clinical syndrome of clubbing of the digits of the hands and feet, enlargement of the extremtities secondary to periarticular and osseous proliferation, and painful and swollen joints. There are two main types of HOA: primary (idiopathic) and secondary. The primary form, also known as pachydermoperiostosis, is a fairly rare autosomal dominant disorder that only represents about 3 - 5 % of all cases of HOA.
The secondary form of HOA is the best known, and is so called because it is generally associated with varous malignancies or chronic infections of the lung or pleura. Because of this association, an earlier name for this syndrome was hypertrophic pulmonary osteoarthropathy. However, since the primary site of disease may lie elsewhere, such as the gut, cardiovascular, hepatobiliary, and endocrine systems, this designation has fallen into disuse, and the term hypertrophic osteoarthropathy is now preferred.
There is now strong evidence that hypertrophic osteoarthropathy and clubbing is due to the peripheral impaction of megakaryocytes and platelet clumps in the fingers and toes. Normally, the pulmonary bed retains these particles, and they fragment before entering the systemic circulation. However, many of the entities associated with HOA and clubbing also are associated with some type of right-to-left shunt. For example, liver disease may be associated with multiple small pulmonary arteriovenous anastomoses. In the presence of such a shunt, these platelet particles can bypass the pulmonary bed. These particles contain and release platelet-derived growth factor (PDGF), whose known effects probably explain all of the pathological changes seen in clubbing. HOA may share the same mechanism, but an additional growth factor derived from the lungs may also play a role.
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