<?php
    global $post;
    query_posts ('cat=4 &posts_per_page=1'); ?>
  <?php if ( have_posts() ) : ?>
 <?php while (have_posts()) : the_post(); ?>

 <h4>
<?php
the_tags( __( ' ',
' ' ), ', ', '<br />'); ?> </p><?php
$posttags = get_the_tags($post->ID);?>
</h4>

<?php
$tags = wp_get_post_tags($post->ID);
if ($tags) {
  echo '';
  $first_tag = $tags[0]->term_id;
  $args=array(
    'tag__in' => array($first_tag),
   'showposts'=>-0,
    'caller_get_posts'=>1,
    'order'    => 'ASC'
);


  $my_query = new WP_Query($args);

  if( $my_query->have_posts() )

 {

while ($my_query->have_posts()) : $my_query->the_post(); ?>

<p><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"> <?php the_title(); ?> </a></p>
      <?php endwhile;}}?>

<!-- /html code -->
    <?php endwhile; ?>
    <?php else : ?>
        <!-- html code if nothing found -->
    <?php endif; ?>
    <?php wp_reset_query();?>