[Erythropoietic protoporphyria : Clinical manifestations, diagnosis and new therapeutic possibilities]

[An overview of porphyrias]

Porphyrias are predominantly genetic metabolic disorders caused by dysregulation of specific enzymes in porphyrin-heme biosynthesis. The enzymatic dysfunction leads to formation and excretion of intermediate metabolic products in the form of porphyrins and/or their precursors δ‑aminolevulinic acid and porphobilinogen, which have cyto- and tissue-toxic properties. Clinically, porphyrias are extremely diverse, with symptoms ranging from skin changes on light-exposed areas of the body to potentially life-threatening neurovisceral attacks. Biochemical tests in urine, blood and stool are used for diagnosis, which can be supplemented by molecular genetic analyses. Treatment of the various forms of porphyria is complex and often requires close interdisciplinary cooperation between different medical specialties.

The Porphyrias

The porphyrias are clinically variable and genetically heterogeneous, predominantly hereditary metabolic diseases, which are caused by a dysfunction of specific enzymes in heme biosynthesis. Here, we provide an overview of the etiopathogenesis, clinic, differential diagnosis, laboratory diagnostics and therapy of these complex metabolic disorders and cover in detail the most common form of porphyria worldwide (porphyria cutanea tarda), the most frequent childhood porphyria (erythropoietic protoporphyria), and the most common neurocutaneous porphyria (variegate porphyria).

A new visible light absorbing organic filter offers superior protection against pigmentation by wavelengths at the UVR-visible boundary region

Skin pigmentation by solar ultraviolet radiation (UVR; ~295-400 nm) is well established. More recently, visible light (VL; 400-740 nm) has been shown to induce rapid pigmentation. Such pigmentation is thought to be caused by oxidative stress, which has associations with skin cancer and photoageing. However, the UVR-VL boundary region has been less well studied. The lower back of healthy Fitzpatrick skin type II-IV individuals was irradiated with increasing doses of narrow-band 385 nm and 405 nm radiation. Pigmentation change was measured immediately, 6 h and 24 h post-irradiation using two reflectance spectroscopy devices and visual grading. Pigmentation was dose-dependently increased in all skin types and time points for both spectra. Two sunscreens, both labelled SPF 15 and UVA protective in the EU and USA (but with different Boots star rating in the UK, 2* vs 5*) were compared. Their formulations were the same apart from the addition of a new organic filter bis-(diethylaminohydroxybenzoyl benzoyl) piperazine (BDBP) that absorbs between 350 and 425 nm. The product that lacked BDBP provided minimal protection against pigmentation, but its addition provided almost complete protection. This demonstrates the needs to improve photoprotection at the UVR-visible border and for sunscreens to act as neutral density filters.

Vemurafenib-related photosensitivity

Increased photosensitivity is a common cutaneous adverse effect associated with the BRAF inhibitor vemurafenib. Clinically, it presents as an immediate sensation of heat and edematous erythema during sun exposure, as well as a sunburn reaction in terms of a late reaction. Phototesting has shown that the UVA range (320 nm to 400 nm), triggers both the immediate and the late reaction. In terms of pathogenesis, photochemical studies have suggested that exposure of vemurafenib to UVA radiation produces an UVA-absorbing photoproduct. In vitro studies on various cell models have also demonstrated that the phototoxic effects of vemurafenib are exclusively caused by UVA irradiation. This latter mechanism is probably responsible for the photosensitivity clinically observed in patients receiving vemurafenib. In addition, vemurafenib is able to inhibit ferrochelatase. The resulting increase in protoporphyrin IX has also been observed in some human studies involving the drug. However, it is yet unproven whether porphyrins actually contribute to the immediate skin reactions seen in individuals on vemurafenib, even though the clinical presentation is similar to that found in erythropoietic protoporphyria with a comparable pathomechanism. Other BRAF inhibitors, such as dabrafenib and encorafenib, are associated with significantly lower photosensitivity. It is essential that patients treated with vemurafenib are informed about immediate and delayed reactions potentially caused even by low doses of UVA. This includes counseling on photoprotective measures.

MR scanning, tattoo inks, and risk of thermal burn: An experimental study of iron oxide and organic pigments: Effect on temperature and magnetic behavior referenced to chemical analysis

BACKGROUND

Tattooed persons examined with magnetic resonance imaging (MRI) can develop burning sensation suggested in the literature to be thermal burn from the procedure. MRI-induced thermal effect and magnetic behavior of known tattoo pigments were examined ex vivo.

MATERIALS AND METHODS

Magnetic resonance imaging effects on 3 commonly used commercial ink stock products marketed for cosmetic tattooing was studied. A main study tested 22 formulations based on 11 pigment raw materials, for example, one line of 11 called pastes and another called dispersions. Samples were spread in petri dishes and tested with a 0.97 T neodymium solid magnet to observe visual magnetic behavior. Before MRI, the surface temperature of the ink was measured using an infrared probe. Samples were placed in a clinical 3T scanner. Two scans were performed, that is, one in the isocenter and one 30 cm away from the center. After scanning, the surface temperature was measured again. Chemical analysis of samples was performed by mass spectroscopy.

RESULTS

Mean temperature increase measured in the isocenter ranged between 0.14 and 0.26°C (P < .01) and in the off-center position from -0.16 to 0.21°C (P < .01). Such low increase of temperature is clinically irrelevant. Chemical analysis showed high concentrations of iron, but also nickel and chrome were found as contaminants. High concentration of iron was not associated with any increase of temperature or any physical draw or move of ink.

CONCLUSION

The study could not confirm any clinically relevant temperature increase of tattoo pigments after MRI.