Protoporphyrias

Pathophysiology and Cellular Genetics

How Protoporphyrin IX (PPIX) Builds Up

In the final step of heme synthesis, the enzyme ferrochelatase (FECH) inserts an iron ion (Fe2+) into protoporphyrin IX (PPIX) to make finished heme.

• In EPP (autosomal recessive/dominant inheritance): Mutations in the FECH gene reduce FECH activity by 65–85%. Without enough of the iron-inserting enzyme, very large amounts of PPIX accumulate in reticulocytes in the bone marrow.
• In XLP (X-linked inheritance): Mutations in the ALAS2 gene make the ALAS2 enzyme overactive, generating far more PPIX than FECH can handle, even though FECH activity itself is normal.

Why the Skin Burns and the Liver Is Damaged

• Fat solubility and burning pain: Unlike water-soluble uroporphyrin, PPIX dissolves in fat. Once in the circulation, it binds tightly to the membranes of endothelial cells lining the dermal capillaries.
• Soret-band activation and phototoxicity: When exposed to visible light (400–410 nm), PPIX releases reactive oxygen species (ROS) that directly damage endothelial cells, dilate capillaries and release histamine and other inflammatory mediators. This strongly stimulates sensory nerve endings and produces severe burning pain, often described as feeling like acid on the skin or fire beneath it.
• Hepatobiliary toxicity (protoporphyric hepatopathy): Because it is not water-soluble, PPIX cannot be cleared by the kidneys and must instead pass through the liver into bile. When levels are very high, PPIX forms hard crystals in liver cells and bile canaliculi, causing biliary obstruction, hepatitis, cirrhosis and acute liver failure (in about 2–5% of patients).

Key Differences: EPP vs. XLP vs. PCT

Typical Clinical Features of Protoporphyria

Symptoms of protoporphyria usually begin very early in childhood (ages 1–3), during a child's first outings to play outdoors.

Acute Skin Symptoms (Acute Photosensitivity)

• Intense burning pain: Within minutes of exposure to sunlight (or light through a window), the patient feels itching, stinging and prickling that quickly turns into severe burning pain.
• Skin that initially looks "normal": What makes the disease so easy to misdiagnose is that, in the first hours of a pain attack, the exposed skin looks completely normal or only slightly red, so others may suspect the patient is "faking it."
• Later swelling and sensitivity: After 12–24 hours, exposed skin (face, backs of the hands) becomes swollen, red and raised, with persistent red patches. Blisters are very rare (seen only in a few children).
• "Priming" (prolonged sensitivity): After an acute attack, the skin becomes extremely sensitive. Even a very small amount of light or mild warmth can set off pain again, lasting for weeks.

Chronic Features and Complications

• Thickened, leathery skin and shallow scars (lichenification): Years of repeated injury leave the skin on the backs of the hands and fingers thick and rough with deepened skin creases, along with small, shallow "orange-peel" or pock-like scars around the lips and on the bridge of the nose.
• Serious liver and biliary complications:
  • Patients may develop yellowing of the skin and eyes, pain under the right ribs and dark urine (from raised bilirubin, not porphyrins).
  • Acute liver failure can progress rapidly when PPIX crystals cause widespread death of liver cells.

How We Diagnose Protoporphyria at Haute-Derma

Because urine is completely normal in protoporphyria, standard urine porphyrin tests miss 100% of cases. Haute-Derma uses a specialized diagnostic workup:

Blood and Spectroscopic Analysis

• Erythrocyte protoporphyrin (RBC PPIX): The gold-standard test. Total erythrocyte PPIX is 5–50 times higher than normal.
• High-performance liquid chromatography (HPLC): Accurately separates free PPIX (overwhelmingly raised in EPP) from zinc-PPIX (raised in XLP).
• Plasma fluorescence spectroscopy: With excitation at 400 nm, plasma shows a characteristic emission peak at 634 nm.

Liver Function and Genetic Screening

• Hepatobiliary assessment: Regular monitoring of liver enzymes (ALT, AST, GGT), total and direct bilirubin and plasma PPIX levels, plus liver elastography (FibroScan) to detect fibrosis early.
• Gene sequencing: Identifies mutations in the FECH gene on chromosome 18q21.31 or the ALAS2 gene on chromosome Xp11.21.

Comprehensive Treatment and Management at Haute-Derma

The goals of treatment are to raise the skin's light tolerance, reduce how often acute burning attacks occur, protect the liver and deal promptly with hepatobiliary complications.

Raising Light Tolerance and Protecting the Skin

• Afamelanotide (Scenesse):
  • A synthetic analogue of alpha-melanocyte-stimulating hormone (α-MSH), given as a 16 mg implant under the skin every 2 months.
  • It boosts melanin production in the skin without sun exposure, creating a natural shield against Soret-band light so patients can spend longer outdoors without pain.
• Dersimelagon: A new-generation oral drug acting on the melanocortin-1 receptor (MC1R), which has shown very promising results in clinical trials for improving light tolerance.
• Tinted mineral sunscreen: Only sunscreens containing iron oxide and zinc oxide can block visible light (400–410 nm). Ordinary chemical sunscreens offer no protection at all.
• Oral beta-carotene: High doses (120–180 mg/day) help neutralize ROS in the skin and reduce light sensitivity in some patients.

Protecting and Treating the Liver

• Rapidly lowering PPIX levels:
  • Cholestyramine or activated charcoal: These bind PPIX in the gut and interrupt its enterohepatic circulation, increasing PPIX elimination in the stool.
  • Ursodeoxycholic acid (UDCA): Stimulates bile flow and protects liver cells from the toxicity of PPIX crystals.
• Red cell transfusion and heme therapy (hemin / hematin): When plasma PPIX climbs high enough to threaten liver failure, blood transfusion or hematin helps switch off PPIX production in the bone marrow through feedback inhibition.
• Liver transplantation and hematopoietic stem cell transplantation (HSCT):
  • In end-stage liver failure, liver transplantation is essential to save the patient's life.
  • However, a liver transplant only fixes the damage in the liver; the bone marrow keeps producing PPIX that will injure the new liver. Hematopoietic stem cell transplantation (HSCT), alongside or after liver transplantation, is therefore the only treatment that cures the underlying cause of EPP/XLP.