-"additions to HTML groups
-syn region htmlItalic start="\\\@<!\*\ze[^\\\*\s]" end="[^\\\*\s]\zs\*" keepend oneline
-syn region htmlItalic start="\\\@<!_\ze[^\\_\s]" end="[^\\_\s]\zs_" keepend oneline
-syn region htmlBold start="\*\*\ze\S" end="\S\zs\*\*" keepend oneline
-syn region htmlBold start="__\ze\S" end="\S\zs__" keepend oneline
-syn region htmlBoldItalic start="\*\*\*\ze\S" end="\S\zs\*\*\*" keepend oneline
-syn region htmlBoldItalic start="___\ze\S" end="\S\zs___" keepend oneline
+let s:conceal = ''
+let s:concealends = ''
+if has('conceal') && get(g:, 'vim_markdown_conceal', 1)
+ let s:conceal = ' conceal'
+ let s:concealends = ' concealends'
+endif
+
+" additions to HTML groups
+if get(g:, 'vim_markdown_emphasis_multiline', 1)
+ let s:oneline = ''
+else
+ let s:oneline = ' oneline'
+endif
+syn region mkdItalic matchgroup=mkdItalic start="\%(\*\|_\)" end="\%(\*\|_\)"
+syn region mkdBold matchgroup=mkdBold start="\%(\*\*\|__\)" end="\%(\*\*\|__\)"
+syn region mkdBoldItalic matchgroup=mkdBoldItalic start="\%(\*\*\*\|___\)" end="\%(\*\*\*\|___\)"
+execute 'syn region htmlItalic matchgroup=mkdItalic start="\%(^\|\s\)\zs\*\ze[^\\\*\t ]\%(\%([^*]\|\\\*\|\n\)*[^\\\*\t ]\)\?\*\_W" end="[^\\\*\t ]\zs\*\ze\_W" keepend' . s:oneline . s:concealends
+execute 'syn region htmlItalic matchgroup=mkdItalic start="\%(^\|\s\)\zs_\ze[^\\_\t ]" end="[^\\_\t ]\zs_\ze\_W" keepend' . s:oneline . s:concealends
+execute 'syn region htmlBold matchgroup=mkdBold start="\%(^\|\s\)\*\*\ze\S" end="\S\zs\*\*" keepend' . s:oneline . s:concealends
+execute 'syn region htmlBold matchgroup=mkdBold start="\%(^\|\s\)\zs__\ze\S" end="\S\zs__" keepend' . s:oneline . s:concealends
+execute 'syn region htmlBoldItalic matchgroup=mkdBoldItalic start="\%(^\|\s\)\zs\*\*\*\ze\S" end="\S\zs\*\*\*" keepend' . s:oneline . s:concealends
+execute 'syn region htmlBoldItalic matchgroup=mkdBoldItalic start="\%(^\|\s\)\zs___\ze\S" end="\S\zs___" keepend' . s:oneline . s:concealends