Lead poisoning has also been found to be the cause of anaemia in a number of cases as lead inhibits porphobilinogen synthase and ferrochelatase, preventing both porphobilinogen formation and the incorporation of iron into protoporphyrin IX, which prevents heme synthesis (Cohen et al., 1981) or causes ineffective heme synthesis and subsequently microcytic anaemia. Here, ALAD is linked to anemia (phenotype).