In the group of patients taking MTX, serious side effects with subsequent drug discontinuation were reported in five patients: methotrexate-induced pneumonitis at the 11th month of MTX therapy at a dose of 10 mg/week in one case; in two patients—an increase in ALT more than three times compared to the normal level; and in two patients—leukocytopenia with a leukocyte level below 3.5 × 109/L after long-term treatment (more than 6 months). Here, GPT is linked to pneumonitis.