diff --git a/runtime/syntax/markdown.vim b/runtime/syntax/markdown.vim
index 1955a74..0321ca3 100644
--- a/runtime/syntax/markdown.vim
+++ b/runtime/syntax/markdown.vim
@@ -2,7 +2,7 @@
 " Language:     Markdown
 " Maintainer:   Tim Pope <vimNOSPAM@tpope.org>
 " Filenames:    *.markdown
-" Last Change:  2016 Aug 29
+" Last Change:  2019 Dec 05
 
 if exists("b:current_syntax")
   finish
@@ -18,37 +18,46 @@
 if !exists('g:markdown_fenced_languages')
   let g:markdown_fenced_languages = []
 endif
+let s:done_include = {}
 for s:type in map(copy(g:markdown_fenced_languages),'matchstr(v:val,"[^=]*$")')
+  if has_key(s:done_include, matchstr(s:type,'[^.]*'))
+    continue
+  endif
   if s:type =~ '\.'
     let b:{matchstr(s:type,'[^.]*')}_subtype = matchstr(s:type,'\.\zs.*')
   endif
   exe 'syn include @markdownHighlight'.substitute(s:type,'\.','','g').' syntax/'.matchstr(s:type,'[^.]*').'.vim'
   unlet! b:current_syntax
+  let s:done_include[matchstr(s:type,'[^.]*')] = 1
 endfor
 unlet! s:type
+unlet! s:done_include
 
-syn sync minlines=10
+if !exists('g:markdown_minlines')
+  let g:markdown_minlines = 50
+endif
+execute 'syn sync minlines=' . g:markdown_minlines
 syn case ignore
 
-syn match markdownValid '[<>]\c[a-z/$!]\@!'
-syn match markdownValid '&\%(#\=\w*;\)\@!'
+syn match markdownValid '[<>]\c[a-z/$!]\@!' transparent contains=NONE
+syn match markdownValid '&\%(#\=\w*;\)\@!' transparent contains=NONE
 
 syn match markdownLineStart "^[<@]\@!" nextgroup=@markdownBlock,htmlSpecialChar
 
 syn cluster markdownBlock contains=markdownH1,markdownH2,markdownH3,markdownH4,markdownH5,markdownH6,markdownBlockquote,markdownListMarker,markdownOrderedListMarker,markdownCodeBlock,markdownRule
-syn cluster markdownInline contains=markdownLineBreak,markdownLinkText,markdownItalic,markdownBold,markdownCode,markdownEscape,@htmlTop,markdownError
+syn cluster markdownInline contains=markdownLineBreak,markdownLinkText,markdownItalic,markdownBold,markdownCode,markdownEscape,@htmlTop,markdownError,markdownValid
 
 syn match markdownH1 "^.\+\n=\+$" contained contains=@markdownInline,markdownHeadingRule,markdownAutomaticLink
 syn match markdownH2 "^.\+\n-\+$" contained contains=@markdownInline,markdownHeadingRule,markdownAutomaticLink
 
 syn match markdownHeadingRule "^[=-]\+$" contained
 
-syn region markdownH1 matchgroup=markdownHeadingDelimiter start="##\@!"      end="#*\s*$" keepend oneline contains=@markdownInline,markdownAutomaticLink contained
-syn region markdownH2 matchgroup=markdownHeadingDelimiter start="###\@!"     end="#*\s*$" keepend oneline contains=@markdownInline,markdownAutomaticLink contained
-syn region markdownH3 matchgroup=markdownHeadingDelimiter start="####\@!"    end="#*\s*$" keepend oneline contains=@markdownInline,markdownAutomaticLink contained
-syn region markdownH4 matchgroup=markdownHeadingDelimiter start="#####\@!"   end="#*\s*$" keepend oneline contains=@markdownInline,markdownAutomaticLink contained
-syn region markdownH5 matchgroup=markdownHeadingDelimiter start="######\@!"  end="#*\s*$" keepend oneline contains=@markdownInline,markdownAutomaticLink contained
-syn region markdownH6 matchgroup=markdownHeadingDelimiter start="#######\@!" end="#*\s*$" keepend oneline contains=@markdownInline,markdownAutomaticLink contained
+syn region markdownH1 matchgroup=markdownH1Delimiter start="##\@!"      end="#*\s*$" keepend oneline contains=@markdownInline,markdownAutomaticLink contained
+syn region markdownH2 matchgroup=markdownH2Delimiter start="###\@!"     end="#*\s*$" keepend oneline contains=@markdownInline,markdownAutomaticLink contained
+syn region markdownH3 matchgroup=markdownH3Delimiter start="####\@!"    end="#*\s*$" keepend oneline contains=@markdownInline,markdownAutomaticLink contained
+syn region markdownH4 matchgroup=markdownH4Delimiter start="#####\@!"   end="#*\s*$" keepend oneline contains=@markdownInline,markdownAutomaticLink contained
+syn region markdownH5 matchgroup=markdownH5Delimiter start="######\@!"  end="#*\s*$" keepend oneline contains=@markdownInline,markdownAutomaticLink contained
+syn region markdownH6 matchgroup=markdownH6Delimiter start="#######\@!" end="#*\s*$" keepend oneline contains=@markdownInline,markdownAutomaticLink contained
 
 syn match markdownBlockquote ">\%(\s\|$\)" contained nextgroup=@markdownBlock
 
@@ -70,31 +79,40 @@
 syn region markdownUrlTitle matchgroup=markdownUrlTitleDelimiter start=+'+ end=+'+ keepend contained
 syn region markdownUrlTitle matchgroup=markdownUrlTitleDelimiter start=+(+ end=+)+ keepend contained
 
-syn region markdownLinkText matchgroup=markdownLinkTextDelimiter start="!\=\[\%(\_[^]]*]\%( \=[[(]\)\)\@=" end="\]\%( \=[[(]\)\@=" nextgroup=markdownLink,markdownId skipwhite contains=@markdownInline,markdownLineStart
+syn region markdownLinkText matchgroup=markdownLinkTextDelimiter start="!\=\[\%(\%(\_[^][]\|\[\_[^][]*\]\)*]\%( \=[[(]\)\)\@=" end="\]\%( \=[[(]\)\@=" nextgroup=markdownLink,markdownId skipwhite contains=@markdownInline,markdownLineStart
 syn region markdownLink matchgroup=markdownLinkDelimiter start="(" end=")" contains=markdownUrl keepend contained
 syn region markdownId matchgroup=markdownIdDelimiter start="\[" end="\]" keepend contained
 syn region markdownAutomaticLink matchgroup=markdownUrlDelimiter start="<\%(\w\+:\|[[:alnum:]_+-]\+@\)\@=" end=">" keepend oneline
 
-let s:concealends = has('conceal') ? ' concealends' : ''
-exe 'syn region markdownItalic matchgroup=markdownItalicDelimiter start="\S\@<=\*\|\*\S\@=" end="\S\@<=\*\|\*\S\@=" keepend contains=markdownLineStart' . s:concealends
-exe 'syn region markdownItalic matchgroup=markdownItalicDelimiter start="\S\@<=_\|_\S\@=" end="\S\@<=_\|_\S\@=" keepend contains=markdownLineStart' . s:concealends
-exe 'syn region markdownBold matchgroup=markdownBoldDelimiter start="\S\@<=\*\*\|\*\*\S\@=" end="\S\@<=\*\*\|\*\*\S\@=" keepend contains=markdownLineStart,markdownItalic' . s:concealends
-exe 'syn region markdownBold matchgroup=markdownBoldDelimiter start="\S\@<=__\|__\S\@=" end="\S\@<=__\|__\S\@=" keepend contains=markdownLineStart,markdownItalic' . s:concealends
-exe 'syn region markdownBoldItalic matchgroup=markdownBoldItalicDelimiter start="\S\@<=\*\*\*\|\*\*\*\S\@=" end="\S\@<=\*\*\*\|\*\*\*\S\@=" keepend contains=markdownLineStart' . s:concealends
-exe 'syn region markdownBoldItalic matchgroup=markdownBoldItalicDelimiter start="\S\@<=___\|___\S\@=" end="\S\@<=___\|___\S\@=" keepend contains=markdownLineStart' . s:concealends
+let s:concealends = ''
+if has('conceal') && get(g:, 'markdown_syntax_conceal', 1) == 1
+  let s:concealends = ' concealends'
+endif
+exe 'syn region markdownItalic matchgroup=markdownItalicDelimiter start="\S\@<=\*\|\*\S\@=" end="\S\@<=\*\|\*\S\@=" skip="\\*" contains=markdownLineStart,@Spell' . s:concealends
+exe 'syn region markdownItalic matchgroup=markdownItalicDelimiter start="\w\@<!_\S\@=" end="\S\@<=_\w\@!" skip="\\_" contains=markdownLineStart,@Spell' . s:concealends
+exe 'syn region markdownBold matchgroup=markdownBoldDelimiter start="\S\@<=\*\*\|\*\*\S\@=" end="\S\@<=\*\*\|\*\*\S\@=" skip="\\*" contains=markdownLineStart,markdownItalic,@Spell' . s:concealends
+exe 'syn region markdownBold matchgroup=markdownBoldDelimiter start="\w\@<!__\S\@=" end="\S\@<=__\w\@!" skip="\\_" contains=markdownLineStart,markdownItalic,@Spell' . s:concealends
+exe 'syn region markdownBoldItalic matchgroup=markdownBoldItalicDelimiter start="\S\@<=\*\*\*\|\*\*\*\S\@=" end="\S\@<=\*\*\*\|\*\*\*\S\@=" skip="\\*" contains=markdownLineStart,@Spell' . s:concealends
+exe 'syn region markdownBoldItalic matchgroup=markdownBoldItalicDelimiter start="\w\@<!___\S\@=" end="\S\@<=___\w\@!" skip="\\_" contains=markdownLineStart,@Spell' . s:concealends
 
 syn region markdownCode matchgroup=markdownCodeDelimiter start="`" end="`" keepend contains=markdownLineStart
 syn region markdownCode matchgroup=markdownCodeDelimiter start="`` \=" end=" \=``" keepend contains=markdownLineStart
-syn region markdownCode matchgroup=markdownCodeDelimiter start="^\s*```.*$" end="^\s*```\ze\s*$" keepend
+syn region markdownCode matchgroup=markdownCodeDelimiter start="^\s*````*.*$" end="^\s*````*\ze\s*$" keepend
 
 syn match markdownFootnote "\[^[^\]]\+\]"
 syn match markdownFootnoteDefinition "^\[^[^\]]\+\]:"
 
 if main_syntax ==# 'markdown'
+  let s:done_include = {}
   for s:type in g:markdown_fenced_languages
-    exe 'syn region markdownHighlight'.substitute(matchstr(s:type,'[^=]*$'),'\..*','','').' matchgroup=markdownCodeDelimiter start="^\s*```\s*'.matchstr(s:type,'[^=]*').'\>.*$" end="^\s*```\ze\s*$" keepend contains=@markdownHighlight'.substitute(matchstr(s:type,'[^=]*$'),'\.','','g')
+    if has_key(s:done_include, matchstr(s:type,'[^.]*'))
+      continue
+    endif
+    exe 'syn region markdownHighlight'.substitute(matchstr(s:type,'[^=]*$'),'\..*','','').' matchgroup=markdownCodeDelimiter start="^\s*````*\s*\%({.\{-}\.\)\='.matchstr(s:type,'[^=]*').'}\=\S\@!.*$" end="^\s*````*\ze\s*$" keepend contains=@markdownHighlight'.substitute(matchstr(s:type,'[^=]*$'),'\.','','g') . s:concealends
+    let s:done_include[matchstr(s:type,'[^.]*')] = 1
   endfor
   unlet! s:type
+  unlet! s:done_include
 endif
 
 syn match markdownEscape "\\[][\\`*_{}()<>#+.!-]"
@@ -107,6 +125,12 @@
 hi def link markdownH5                    htmlH5
 hi def link markdownH6                    htmlH6
 hi def link markdownHeadingRule           markdownRule
+hi def link markdownH1Delimiter           markdownHeadingDelimiter
+hi def link markdownH2Delimiter           markdownHeadingDelimiter
+hi def link markdownH3Delimiter           markdownHeadingDelimiter
+hi def link markdownH4Delimiter           markdownHeadingDelimiter
+hi def link markdownH5Delimiter           markdownHeadingDelimiter
+hi def link markdownH6Delimiter           markdownHeadingDelimiter
 hi def link markdownHeadingDelimiter      Delimiter
 hi def link markdownOrderedListMarker     markdownListMarker
 hi def link markdownListMarker            htmlTagName