Hi,
It could be a progressing rare/life-threatening complication of histiocytosis [
internal jugular vein thrombosis with lung collapse], called
Rosai Dorfman disease, so check with the relevant investigation(s) like
complete blood count, ESR, CRP, sputum for AFB,
rheumatoid factor, antiphospholipid antibodies, anti cardiolipin antibodies, along with CT venogram of the neck, 2D echo, CXR for lung collapse/consolidation,
ultrasonography of the neck. The attending physician might start with anti-coagulants [initially sub cutaneous and later oral], steroids, and empirical antibiotics, and after repeat with CT chest.
Take care. Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. Munish Sood, Ayurveda Specialist