Porphyrias

Inherited and acquired
Hepatic and erythropoietic
all are autosomal dominant except CEP

Mnemonic to remember heme synthesis pathway

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Enzymes
-As
Ad
U1
U3
Ud
Co
Po
F

Reason for abdominal pain and neuropsychiatric symptoms

The exact mechanism is not known but it is thought to be due to accumulation of ALA, phorphobilinogen and hydroxymethylbilane.
The neurological symptoms are due to decrease activity of tryptophan pyrrolase,
which causes accumulation of tryptophan and serotonin (5-hydroxy tryptamine)
ALA causes impaired nerve conduction

Reason for photosensitivity and cutaneous manifestations

Porphyrinogen get accumulated when defect is below the hydroxymethylbilane.
On oxidation these porphyrinogens are converted into porphyrins and cause
photosensitivity. When exposed to light, porphyrin reacts with O2 to from free
radicals (ROS). Reactive oxygen species causes lysosomal damage and release of
degradative enzymes which lead to the cutaneous manifestations (skin injuries).

Видео Porphyrias канала Biochemistry by Dr Rajesh Jambhulkar