Bronchogenic carcinoma = lung cancer

That being said, lung adenocarcinoma specifically is associated with hypertrophic osteoarthropathy, which is a paraneoplastic syndrome characterized by digital clubbing, arthralgia, joint effusions, and periostosis of tubular bones

found this online: https://academic.oup.com/rheumap/article/2/1/rky009/5040548

Hypertrophic pulmonary osteoarthropathy (HPOA) is a syndrome characterized by the triad of periostitis, digital clubbing and painful arthropathy of the large joints, especially involving the lower limbs. Clubbing is characterized by bulbous enlargement of terminal segments of the fingers and toes due to proliferation of subungual connective tissue.

primary... is a rare hereditary condition.

A majority of cases (>90%) of secondary HPOA are associated with pulmonary malignancies [6] or chronic suppurative pulmonary diseases.

Pulmonary malignancies, including primary [7], metastatic lung cancer and intrathoracic lymphoma, account for 80% of cases of secondary HPOA. Adenocarcinoma of the lung is the most frequent and small cell carcinoma is the least frequent histopathologic type of lung cancer associated with HPOA [7].

other associated extrathoracic malignancies include nasopharyngeal carcinoma, renal cell carcinoma, oesophageal cancer, gastric tumour [8], pancreatic cancer, breast phyllodes tumour [9], melanoma, thyroid cancer, osteosarcoma and intestinal lymphoma.

Various rheumatologic conditions, including RA [10], AS [11], polyarteritis nodosa, SLE [12], Takayasu disease [13], sarcoidosis, APS and Mediterranean fever are known to be associated with this condition as well.

Pulmonary conditions such as cystic fibrosis, tuberculosis, idiopathic pulmonary fibrosis [14] and lung transplantation have also been associated with HPOA.

I believe this is Caplan Syndrome (bronchogenic carcinoma + rheumatoid arthritis). Only flaw to that is that the pulmonary findings don't perfectly represent pneumoconioses.

The reported incidence of Caplan syndrome is 1 in every 100,000 people. This has been a declining number due to lower exposure to coal, asbestos, and silica. Prevalence of Caplan syndrome is higher in patients with silica exposure compared to the other causes. The first epidemiologic study undertaken by the Pneumoconiosis Research Unit observed an increased prevalence of RA amongst men with progressive massive fibrosis (PMF). Miall et al. found no increased prevalence of rheumatoid arthritis in miners when compared to a community where PMF and rheumatoid arthritis were prevalent and therefore concluded that the etiology of RA was not associated with exposure to dust or lung changes of complicated pneumoconiosis. There was a high prevalence rate of PMF and tuberculosis amongst miners and ex-miners with rheumatoid arthritis.[4][5]

Pathophysiology: An autoimmune condition is a phenomenon where one's body has inflammatory cells which attack its own tissue and, in the case of RA, the synovium. It is believed that in these patients, there is an alteration which causes the increased immune response to foreign materials in the lungs. There is immune hyperactivity that is sparked by silica in which monocytes and macrophages release cytokines such as interleukin-1 and granulocyte-macrophage-colony-stimulating factor and tumor necrosis factor alpha. The sharp edges of the silica also cause lysis of lysosomal proteases in macrophages. Lymphocytes are activated by the cytokines released by macrophages. This all leads to an autoimmune phenomenon through exposure to silica which is triggered in genetically predisposed individuals who have RA.

wouldn't the underlying disease be RA which is then causing bronchogenic carcinoma? I'm confused!!