diff --git a/app/models/qa/authorities/mesh.rb b/app/models/qa/authorities/mesh.rb
new file mode 100644
index 0000000..d8f2d1b
--- /dev/null
+++ b/app/models/qa/authorities/mesh.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require Qa::Engine.root.join('lib', 'qa', 'authorities', 'mesh')
+
+module Qa
+  module Authorities
+    ##
+    # Monkeypatch the built in MESH authority to downcase terms.
+    #
+    # @see https://github.com/samvera/questioning_authority/issues/158
+    class Mesh
+      def search(query)
+        Qa::SubjectMeshTerm
+          .where('term_lower LIKE ?', "#{query.to_s.downcase}%")
+          .limit(10)
+          .map { |t| { id: t.term_id, label: t.term } }
+      end
+    end
+  end
+end
diff --git a/spec/features/autocomplete_mesh_spec.rb b/spec/features/autocomplete_mesh_spec.rb
index a70accc..8cfa317 100644
--- a/spec/features/autocomplete_mesh_spec.rb
+++ b/spec/features/autocomplete_mesh_spec.rb
@@ -25,7 +25,7 @@
     click_on 'Additional fields'
 
     # Check that we get the correct autocompletion from QA
-    find('#etd_subject').send_keys 'sulfameraz'
+    find('#etd_subject').send_keys 'SuLFamerAZ'
     expect(page).to have_content('Sulfamerazine')
 
     # Fill out the rest of the form