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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.

Autosomal recessive forms of infantile dystonia due to mutations in the tyrosine hydroxylase (TH) gene have been described recently. The main clinical manifestations are Segawa's disease, or infantile hypokinetic rigid Parkinsonism. Here, we report on a patient with hyperrigidity, psychomotor developmental delay, and dystonic posturing of the hands, symptoms that appeared after a viral infection at the age of 14 months. Low homovanillic acid/5-hydroxyindolacetic acid (HVA/5HIAA) ratio in cerebrospinal fluid suggested a TH deficiency. Molecular analysis revealed a novel (H246Y) and a known (D498G) compound heterozygote mutation in the TH gene. The patient showed a remarkable response to treatment with levodopa. The new mutation and the association of viral infections with the onset and worsening of symptoms are discussed.