Get child record from specific root
MySQL does not feature recursive queries. In fact, Bill Karwin just wrote a blog post about how MySQL is the only major RDBMS without recursive queries. Notwithstanding, what you need is a Stored Procedure that performs the query as a preorder tree traversal using a queue.
YOUR SAMPLE DATA
mysql&gt; drop database if exists ayman;
Query OK, 2 rows affected (0.03 sec)

mysql&gt; create database ayman;
Query OK, 1 row affected (0.00 sec)

mysql&gt; use ayman
Database changed
mysql&gt; create table topics
    -&gt; (id int not null primary key,
    -&gt; parent int default null
    -&gt; ) engine=MyISAM;
Query OK, 0 rows affected (0.05 sec)

mysql&gt; insert into topics (id) values (1),(5);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql&gt; insert into topics (id,parent) values (2,1),(3,2),(4,2);
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql&gt; create table articles
    -&gt; (id int not null,
    -&gt; topic int not null,
    -&gt; featured int not null
    -&gt; ) engine=MyISAM;
Query OK, 0 rows affected (0.13 sec)

mysql&gt; insert into articles values
    -&gt; (1,1,1),(2,2,0),(3,3,1),(4,4,1),(5,5,1);
Query OK, 5 rows affected (0.00 sec)
Records: 5  Duplicates: 0  Warnings: 0

Here it is loaded
mysql&gt; select * from articles order by id;
+----+-------+----------+
| id | topic | featured |
+----+-------+----------+
|  1 |     1 |        1 |
|  2 |     2 |        0 |
|  3 |     3 |        1 |
|  4 |     4 |        1 |
|  5 |     5 |        1 |
+----+-------+----------+
5 rows in set (0.00 sec)

mysql&gt; select * from topics order by id;
+----+--------+
| id | parent |
+----+--------+
|  1 |   NULL |
|  2 |      1 |
|  3 |      2 |
|  4 |      2 |
|  5 |   NULL |
+----+--------+
5 rows in set (0.00 sec)

mysql&gt;

STORED PROCEDURE
DELIMITER $$

DROP FUNCTION IF EXISTS `ayman`.`GetFeaturedArticles` $$
CREATE FUNCTION `ayman`.`GetFeaturedArticles` (GivenID INT) RETURNS VARCHAR(1024)
DETERMINISTIC
BEGIN

    DECLARE rv,rvlist,q,queue,queue_children VARCHAR(1024);
    DECLARE queue_length,front_id,pos INT;

    SET rv = '';
    SET queue = GivenID;
    SET queue_length = 1;

    WHILE queue_length &gt; 0 DO
        SET front_id = FORMAT(queue,0);
        IF queue_length = 1 THEN
            SET queue = '';
        ELSE
            SET pos = LOCATE(',',queue) + 1;
            SET q = SUBSTR(queue,pos);
            SET queue = q;
        END IF;
        SET queue_length = queue_length - 1;

        SELECT IFNULL(qc,'') INTO queue_children FROM
        (
            SELECT GROUP_CONCAT(AA.id) qc
            FROM articles AA INNER JOIN topics BB
            ON AA.topic = BB.id
            WHERE BB.parent = front_id
        ) A;
        IF LENGTH(queue_children) = 0 THEN
            IF LENGTH(queue) = 0 THEN
                SET queue_length = 0;
            END IF;
        ELSE
            IF LENGTH(rv) = 0 THEN
                SET rv = queue_children;
            ELSE
                SET rv = CONCAT(rv,',',queue_children);
            END IF;
            IF LENGTH(queue) = 0 THEN
                SET queue = queue_children;
            ELSE
                SET queue = CONCAT(queue,',',queue_children);
            END IF;
            SET queue_length = LENGTH(queue) - LENGTH(REPLACE(queue,',','')) + 1;
        END IF;
    END WHILE;

    SET rvlist = CONCAT(GivenID,',',rv);
    SET rv = '';
    SET @comma = '';

    #
    # Strip Out Non-Featured Articles
    #
    SET @searching = 1;
    WHILE @searching  = 1 DO
        SET @searching = (LOCATE(',',rvlist) &gt; 1);
        SET front_id = FORMAT(rvlist,0);
        SELECT COUNT(1) INTO @ItsFeatured FROM articles WHERE id = front_id AND featured = 1;
        IF @ItsFeatured = 1 THEN
            SET rv = CONCAT(rv,@comma,front_id);
            SET @comma = ',';
        END IF;
        SET pos = LOCATE(',',rvlist) + 1;
        SET q = SUBSTR(rvlist,pos);
        SET rvlist = q;
    END WHILE;

    RETURN rv;

END $$

DELIMITER ;

Here is the execution of it
mysql&gt; select * from articles;
+----+-------+----------+
| id | topic | featured |
+----+-------+----------+
|  1 |     1 |        1 |
|  2 |     2 |        0 |
|  3 |     3 |        1 |
|  4 |     4 |        1 |
|  5 |     5 |        1 |
+----+-------+----------+
5 rows in set (0.00 sec)

mysql&gt; select * from topics;
+----+--------+
| id | parent |
+----+--------+
|  1 |   NULL |
|  5 |   NULL |
|  2 |      1 |
|  3 |      2 |
|  4 |      2 |
+----+--------+
5 rows in set (0.00 sec)

mysql&gt; select GetFeaturedArticles(1);
+------------------------+
| GetFeaturedArticles(1) |
+------------------------+
| 1,3,4                  |
+------------------------+
1 row in set (0.03 sec)

mysql&gt;

I borrowed this code from my earlier post : Find highest level of a hierarchical field: with vs without CTEs
The Stored Procedure first collects all the descendants of a given article's topic hierarchy. Then, it iterates through the return list and strips non-featured articles.
Give it a Try !!!