X-chromosomal inactivation directly influences the phenotypic manifestation of X-linked protoporphyria

X-linked protoporphyria (XLP), a rare erythropoietic porphyria, results from terminal exon gain-of-function mutations in the ALAS2 gene causing increased ALAS2 activity and markedly increased erythrocyte protoporphyrin levels. Patients present with severe cutaneous photosensitivity and may develop liver dysfunction. XLP was originally reported as X-linked dominant with 100% penetrance in males and females. We characterized 11 heterozygous females from six unrelated XLP families and show markedly varying phenotypic and biochemical heterogeneity, reflecting the degree of X-chromosomal inactivation of the mutant gene. ALAS2 sequencing identified the specific mutation and confirmed heterozygosity among the females. Clinical history, plasma and erythrocyte protoporphyrin levels were determined. Methylation assays of the androgen receptor and zinc-finger MYM type 3 short tandem repeat polymorphisms estimated each heterozygotes X-chromosomal inactivation pattern. Heterozygotes with equal or increased skewing, favoring expression of the wild-type allele had no clinical symptoms and only slightly increased erythrocyte protoporphyrin concentrations and/or frequency of protoporphyrin-containing peripheral blood fluorocytes. When the wild-type allele was preferentially inactivated, heterozygous females manifested the disease phenotype and had both higher erythrocyte protoporphyrin levels and circulating fluorocytes. These findings confirm that the previous dominant classification of XLP is inappropriate and genetically misleading, as the disorder is more appropriately designated XLP.

[Air and biomonitoring of occupational exposure to anesthetic gases in the health care workers of a large hospital in Milan]

In this study exposure to anesthetic gases in health care workers of a hospital of Milan was investigated. The evaluation focused on the period 2007-2010 and was performed by environmental monitoring (20 operating rooms and 54 samples) and biological monitoring (180 workers and 242 urine samples). Mean airborne exposure was 3:15 and 0.34 ppm for nitrogen protoxide (N2O) and sevorane; in end-of-exposure urine samples the concentration of N2O and hexafluoroisopropanol, metabolite of sevorane, were 4.85 mg/L and 0.21 mg/L, with 80 and 21% of values below the quantification limit. Sevorane monitoring exceeded or equaled the environmental limit value of 0.5 ppm and the biological exposure index in 17 and 11% of measures. There were no observed exceedances of the limit for N2O. The anesthetist and scrub nurse were tasks with greater exposure. There was a significant correlation between airborne halogenated gases and urinary hexafluoroisopropanol. The results of this study indicates that further efforts are needed to improve the hygienic conditions in the investigated hospital.

[The assessment of risk for xylene exposure in a laboratory of anatomy: comparison between computational models and environmental and biological monitoring]

Exposure to xylene in a pathology laboratory was evaluated using two algorithms: Stoffenmanager and Archi.me.de. The results were compared with those obtained by applying the environmental and biological monitoring of the exposure. The use of models required a period of self-learning and, for Stoffenmanager, knowledge of the English language. Information on the toxicity and safety of xylene, available from the medial and safety data sheets, and the conditions and amount of use, obtained through a survey and interviews with operators, have been imputed. Stoffenmanager estimated low the inhalation exposure and medium the dermal exposure, with a value of personal exposure during the work shift of 1.4 mg/m3. A.r.chi.me.d.e. estimated negligible the risk to health. These ratings are consistent with those obtained using the experimental approach. This result, combined with the simplicity and low cost, makes the algorithms very interesting tools for the assessment of chemical risk in the workplace.