Porphyrin Distribution and Porphyrin Excretion in Human Congenital Erythropoietic Porphyria

Abstract

A study of the excretion pattern and porphyrin distribution in a case of congenital erythropoietic porphyria has been presented. More than 50% of the porphyrins excreted in the urine are type III isomers, most of which are found in the hepta-, hexa- and pentacarboxylic porphyrins. A tetracarboxylic porphyrin having 3 propionic and 1 acetic acid β-chains and with chromatographic and spectral properties similar to isocoproporphyrin has been found to be excreted in both faeces and urine. This porphyrin seems to be preferentially excreted in the urine. The erythrocytes contain almost entirely protoporphyrin, while the ‘buffy coat’ and bone marrow contain predominantly octa- and heptacarboxylic porphyrins. The pattern found in liver and plasma differs from that of bone marrow and ‘buffy coat’ primarily in showing exceptionally large amounts of an apparent hexacarboxylic porphyrin, while the spleen contains relatively high amounts of uroporphyrin. Trace amounts of an apparent isocoproporphyrin are found in bone marrow, ‘buffy coat’, plasma, and liver, but not in erythrocytes and liver. The findings have been discussed and compared with the urinary porphyrin pattern found in a well-documented case of classical Günther's disease. A block in the normal decarboxylation of the pentacarboxylic intermediate type III in protoporphyrin biosynthesis partially bypassed via an isocoproporphyrin derivative, possibly dehydroisocoproporphyrinogens, is suggested.

Key Words:

• Erythrocyte production
• bimodal
• isocoproporphyrin
• porphyrin decarboxylation