The most prevalent ACHM3 mutation, T383IfsX12, results in a non-functional truncated protein that does not properly traffic to the cell membrane.The three missense mutations that have received further study show a number of aberrant properties, with one underlying theme. The R403Q mutation, which lies in the pore region of the channel, results in an increase in outward current rectification, versus the largely linear current-voltage relationship of wild-type channels, concomitant with an increase in cGMP affinity. The other mutations show either increased (S435F) or decreased (F525N) surface expression but also with increased affinity for cAMP and cGMP. It is the increased affinity for cGMP and cAMP in these mutants that is likely the disorder-causing change. Such increased affinity will result in channels that are insensitive to the slight concentration changes of cGMP due to light input into the retina. ACHM4
Upon activation by light, cone opsin causes the exchange of GDP for GTP in the guanine nucleotide binding protein (G-protein) α-transducing activity polypeptide 2 (GNAT2). This causes the release of the activated α-subunit from the inhibitory β/γ-subunits. This α-subunit then activates a phosphodiesterase that catalyzes the conversion of cGMP to GMP, thereby reducing current through CNG3 channels. As this process is absolutely vital for proper color processing it is not surprising that mutations in GNAT2 lead to achromatopsia. The known mutations in this gene, all result in truncated proteins. Presumably, then, these proteins are non-functional and, consequently, cone opsin that has been activated by light does not lead to altered cGMP levels or photoreceptor membrane hyperpolarization.
It seems to be effective in reducing circulating protoporphyrin levels.Bone marrow transplantation, liver transplantation, acetylcysteine, extracorporeal albumin dialysis, parenteral iron and transfusion of erythrocytes are alternative plans for treatment of EEP. Over-the-counter drug
Some over-the-counter drugs may help:

Proferrin is an oral heme supplement which may work similarly to Hematin. B. subtilis (a gram-positive soil probiotic) produces ferrochelatase, which may be able to convert some of the protoporphyrin in the intestine into heme. Beta carotene, though a recent meta analysis of carotene treatment has called its effectiveness into question. Epidemiology
Case reports suggest that EPP is prevalent globally. The prevalence has been estimated somewhere between 1 in 75,000 and 1 in 200,000 however it has been noted that the prevalence of EPP may be increasing due to a better understanding of the disease and improved diagnosis. An estimated 5,000–10,000 individuals worldwide have EPP. EPP is considered the most common form of porphyria in children. The prevalence in Sweden has been published as 1:180,000. History
Erythropoietic protoporphyria was first described in 1953 by Kosenow and Treibs and completed in 1960 by Magnus et al. at the St Johns Institute of Dermatology in London. See also
Xeroderma pigmentosum
Porphyria cutanea tarda
List of cutaneous conditions

References
External links
Erythropoietic protoporphyria at NLM Genetics Home Reference