Protoporphyrin synthesis is part of heme synthesis; I think the underlying point from the Pathoma here is inability to produce protoporphyrin → overabundance of iron in mitochondria → ringed sideroblasts. Would want to see how this is tested in the tagged UWorld Q before changing
Think we can just expand on this in extra; changing text to this would imply that it is commonly caused directly by a ferrochelatase deficiency when the genetic cause and a lot of the common acquired causes are due to ALAS deficiency (AUD, isoniazid, B6 deficiency) which leads to low protoporphyrin.
(For context: AMBOSS directly tests the isoniazid/B6 def cause and FA23 pg 425 says AUD is the most common cause)