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The diffusion and solubility of HCl in ice have been measured between −5 and −15°C by exposing large single crystals of ice to low vapor pressures of HCl for several days. The solubility is found to be (1.0±0.15) × 10−4 mol/1 at −15°C under a 5.6×10−4 Pa HCl partial pressure. The diffusion coefficient is of the order of 10−12 cm2s−1 at −8°C, but the determination of the value is affected by small angle boundaries, where HCl motion is much faster. Extrapolation of these results suggests that HCl is not incorporated into stratospheric ice crystals.

The occurrence of neurological symptoms and developmental delay in patients affected by congenital hypothyroidism (CH) has been attributed to the lack of thyroid hormone in the developing CNS. Accordingly, after the introduction of neonatal screening programs for CH, which allowed early and adequate treatment, an almost normal outcome for most CH patients could be achieved. However, a few patients did not reach this favorable outcome despite early and adequate treatment. Here we describe five patients with variable degrees of CH who suffered from choreoathetosis, muscular hypotonia, and pulmonary problems, an association of symptoms that had not been described before this study. Since this clinical picture matched the phenotype of mice targeted for deletion of the transcription factor gene Nkx2-1, we investigated the human NKX2-1 gene in these five patients. We found heterozygous loss of function mutations in each of these five patients, e.g., one complete gene deletion, one missense mutation (G2626T), and three nonsense mutations (2595insGG, C2519A, C1302A). Therefore, the unfavorable outcome in patients with CH, especially those with choreoathetosis and pulmonary symptoms, can be explained by mutations in the NKX2-1 gene rather than by hypothyroidism. Moreover, the association of symptoms in the patients with NKX2-1 mutations points to an important role of human NKX2-1 in the development and function of thyroid, basal ganglia, and lung, as already described for rodents.

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