805 ILCS 10/5
A professional corporation organized under this Act may consolidate or merge only with another domestic professional corporation organized under this Act to render the same specific professional service or related professional services or with a domestic limited liability company organized under the Limited Liability Company Act to render the same specific professional service or related professional services and a merger or consolidation with any foreign corporation or foreign limited liability company is prohibited. A professional association organized under the "Act to Authorize Professional Associations", approved August 9, 1961, as amended, may merge with a professional corporation formed under this Act by complying with Section 4 of this Act. A conversion to or from a professional corporation under the Entity Omnibus Act is permitted only if the converted entity is organized to render the same specific professional service or related professional services.
805 ILCS 10/5