The two main sites in the body for accumulation of excess porphyrins are

The two main sites in the body for accumulation of excess porphyrins are

• A. Liver and bone marrow
• B. Heart and lung
• C. Muscle and blood
• D. Liver and spleen

Answer: (A)

Porphyrins are intermediates in heme synthesis, and in adults this production happens mainly in the liver and in developing red blood cells in the bone marrow. When an enzyme in the porphyrin pathway is defective, the accumulating precursor tends to build up where that portion of the pathway is most active. In hepatic porphyrias the liver is the key site of excess porphyrin accumulation, while in erythropoietic porphyrias the bone marrow (and circulating red cells) are the main reservoirs. Because these two tissues handle the bulk of porphyrin production, they are the primary sites where excess porphyrins accumulate. Other organs such as the heart, lungs, muscles, or spleen are not major sites of porphyrin synthesis or storage, so they aren’t typical accumulation sites.

Porphyrins are intermediates in heme synthesis, and in adults this production happens mainly in the liver and in developing red blood cells in the bone marrow. When an enzyme in the porphyrin pathway is defective, the accumulating precursor tends to build up where that portion of the pathway is most active. In hepatic porphyrias the liver is the key site of excess porphyrin accumulation, while in erythropoietic porphyrias the bone marrow (and circulating red cells) are the main reservoirs. Because these two tissues handle the bulk of porphyrin production, they are the primary sites where excess porphyrins accumulate. Other organs such as the heart, lungs, muscles, or spleen are not major sites of porphyrin synthesis or storage, so they aren’t typical accumulation sites.