Agoraphobia can develop as panic disorder progresses. Agoraphobia is the fear of places or situations where escape or help may be difficult if you have a panic attack there. So agoraphobia can occur as a result of panic disorder worsening and progressing (Carandang, 2014).
Reference:
“Chapter 5 – Panic Disorder.” Anxiety Protocol. Carandang C. 2014. Healthy Mind Research Corporation.