Cyanotoxins in inland lakes of the United States: Occurrence and potential recreational health risks in the EPA National Lakes Assessment 2007

A large nation-wide survey of cyanotoxins (1161 lakes) in the United States (U.S.) was conducted during the EPA National Lakes Assessment 2007. Cyanotoxin data were compared with cyanobacteria abundance- and chlorophyll-based World Health Organization (WHO) thresholds and mouse toxicity data to evaluate potential recreational risks. Cylindrospermopsins, microcystins, and saxitoxins were detected (ELISA) in 4.0, 32, and 7.7% of samples with mean concentrations of 0.56, 3.0, and 0.061μg/L, respectively (detections only). Co-occurrence of the three cyanotoxin classes was rare (0.32%) when at least one toxin was detected. Cyanobacteria were present and dominant in 98 and 76% of samples, respectively. Potential anatoxin-, cylindrospermopsin-, microcystin-, and saxitoxin-producing cyanobacteria occurred in 81, 67, 95, and 79% of samples, respectively. Anatoxin-a and nodularin-R were detected (LC/MS/MS) in 15 and 3.7% samples (n=27). The WHO moderate and high risk thresholds for microcystins, cyanobacteria abundance, and total chlorophyll were exceeded in 1.1, 27, and 44% of samples, respectively. Complete agreement by all three WHO microcystin metrics occurred in 27% of samples. This suggests that WHO microcystin metrics based on total chlorophyll and cyanobacterial abundance can overestimate microcystin risk when compared to WHO microcystin thresholds. The lack of parity among the WHO thresholds was expected since chlorophyll is common amongst all phytoplankton and not all cyanobacteria produce microcystins.

Phenotypic variability in trisomy 13 mosaicism: two new patients and literature review

Trisomy 13 mosaicism occurs when two cell lines, one with a normal complement of chromosomes and the other with an additional chromosome 13, are present in the same individual. We present two children with trisomy 13 mosaicism and summarize the literature in 47 published cases. Our first patient is a 4-year-old male with normal development and dysmorphic features that include right microtia, tall forehead, bulbous nose, and high arched palate. The second patient died at 1 day of life secondary to laryngeal stenosis, a previously undocumented finding in trisomy 13. His other dysmorphic features included micrognathia, cleft soft palate, and an axillary pterygium. Several published case reports of patients with trisomy 13 mosaicism have had the typical phenotype of complete trisomy 13 with death in the neonatal period, while others have had few dysmorphic features and prolonged survival. The most common malformations in all 49 cases included ear anomalies, cleft lip and palate, and various congenital heart defects. Intelligence varied from normal in six patients to significant delays and mental retardation in the remainder of cases. There is no clear correlation between the percentage of trisomic cells and the level of intellectual function. The dysmorphic features seen vary considerably from one patient to the next, often making the clinical diagnosis of trisomy 13 mosaicism difficult. In counseling families, medical professionals should state that trisomy 13 mosaicism may lead to physical abnormalities and poor intellectual outcomes, but that the condition does not do so universally with normal development occurring in some individuals.

A Post Mortem Assessment of a 25-Year-Old Man with Ascending Aortic Dissection and a Novel MYLK Variant

We report on the process of post mortem evaluation and genetic testing following the death of a 25-year-old man due to ascending aortic dissection leading to aortic rupture. Following the negative clinical testing of a 12- gene thoracic aortic aneurysm and dissection panel, research testing revealed a novel c.5732A>T (p.E1911V) variant in exon 34 of the MYLK gene (NM_053025). Two likely pathogenic variants in this gene have been reported previously in individuals with familial thoracic aortic aneurysm and dissection. Given the unclear clinical consequence of the variant found in our proband, we have classified this change as a variant of uncertain significance. In addition to discussing the complexity involved in variant interpretation, we recognize the need for additional research for more accurate MYLK interpretation. Finally, we comment on the unique challenges of post mortem genetic testing.