Brief Answer:
Methotrexate is even prescribed in Rheumatoid arthritis treatment also.

Detailed Answer:

Hello,

Did you mean to say Poliomyelitis? If yes, then please note, that in long run, the neuromuscular involvement of Poliomyelitis does affect the pulmonary vasculature which in turn can show up as prominent broncho-vascular markings. It's a complex process and very chronic, so there may not be any apparent chest/lung symptoms at a glance.

Please don't worry regarding Methotrexate though. Although it's a well-known medication for Chemotherapy, it does have a lot of different mode of actions, which is why it's being widely prescribed in cases of Rheumatoid arthritis as well (as already mentioned in your medical history).

I think the CT-scan will clarify these findings further, which could've been the reason your doctor has suggested them as well.

Let me know if I can assist you further.
Take care.
Regards

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