OOPS, sorry this is the correct mod_rewrite
<VirtualHost *>
ServerName
www.mydomain.com
ServerAdmin wiki(a)mydomain.com
RewriteEngine On
RewriteLog /var/log/wiki_rewrite.log
RewriteLogLevel 2
CustomLog /var/log/wiki_custom.log common
ErrorLog /var/log/wiki_error.log
# use [P] for Proxy and NOT [R] for redirect ! - all in one line
RewriteRule ^/(.*)
http://192.168.1.105/appContext/$1 [L,P,E=proxy_ok:1]
ProxyPreserveHost On
</VirtualHost>