Combine rows from several WHENs into one

[j.taylor]

My query below gives several rows in the output html table that contain the word "infancy" and a value. 

How do I combine all of these into one row with a total, while keeping that row ordered with all the others?

 

So, instead of:

 

5  |  15

75  |  7

infancy  |  4

66  |  3

infancy  |  2

 

I'd get:

 

5  |  15

75  |  7

infancy  |  6

66  |  3

 

 

$sql = "SELECT age, COUNT(age) AS frequency,


   CASE WHEN age = 'inf.' THEN 'infancy'
        WHEN age = '1' THEN 'infancy'
        WHEN age LIKE ('%mos.') THEN 'infancy'
        WHEN age LIKE ('%wks.') THEN 'infancy'
      ELSE age END AS age
         
FROM persons
WHERE age IS NOT NULL 
AND age <> ''
AND age <> '?'
GROUP BY age
ORDER BY frequency DESC, age DESC
LIMIT 100";