Inserting a line break in a PDF generated from XSL FO using <xsl:value-of>
You could also replace <br/>
with 

and add a linefeed-treatment="preserve"
attribute to your <fo:block>
.
Something like:
<fo:block linefeed-treatment="preserve">This is an example Description.
List item 1
List item 2
List item 3
List item 4</fo:block>
Edit
Some users may need to use \n
instead of 

depending on how they are creating the XML. See Retain the 
 during xml marshalling for more details.
This helped me and should be simplest solution (working with Apache FOP 1.1):
Why not replace your <br/>
with Unicode character called line separator.
<xsl:template match="br">
<xsl:value-of select="'
'"/>
</xsl:template>
See https://en.wikipedia.org/wiki/Newline#Unicode
The following code worked:
<fo:block white-space-collapse="false"
white-space-treatment="preserve"
font-size="0pt" line-height="15px">.</fo:block>
It makes the xsl processor thinks this block contains a line of text, which actually has a 0pt font size. You can customize line height by providing your own value.