<prompt> Protoporphyrin levels 100 mgdl indicates:Iron overloadLead poisoningPorphyriaAll of the above  <response>: Protoporphyrin is an intermediate in the pathway to heme synthesis. Under conditions in which heme synthesis is impaired, protoporphyrin accumulates within the red cell. This reflects an inadequate iron supply to erythroid precursors to suppo haemoglobin synthesis. Normal values are 30 mgdL of red cells. In iron deficiency, values in excess of 100 mgdL are seen. The most common causes of increased red cell protoporphyrin levels are absolute or relative iron deficiency and lead poisoning. Ref: Harrisons principle of internal medicine 17th edition, chapter 98. 