Porphyries and colour blindness

Porphyries make a group of hereditary diseases caused by a partial defect in one of the seven enzymes of hem synthesis that generates a characteristic standard of accumulation and excretion of the correspondent precursor. Porphyries prevalence is 1/30000 in general population. Normal colour vision is called trichromasia because it is able to appreciate colour mixtures made with the three basic colours. 8% of men and 1% of women suffer from colour vision defects. A family in which both pathologies coincide is presented: the father suffers from a porphyria cutanea tarda, the youngest brother has a colour vision defect and the eldest brother both pathologies.