KCNQ2 and KCNQ3 are two homologous K ؉ channel subunits that can combine to form heterotetrameric channels with properties of neuronal M channels. Loss-of-function mutations in either subunit can lead to benign familial neonatal convulsions (BFNC), a generalized, idiopathic epilepsy of the newborn. We now describe a syndrome in which BFNC is followed later in life by myokymia, involuntary contractions of skeletal muscles. All affected members of the myokymia͞BFNC family carried a mutation (R207W) that neutralized a charged amino acid in the S4 voltage-sensor segment of KCNQ2. This substitution led to a shift of voltage-dependent activation of KCNQ2 and a dramatic slowing of activation upon depolarization. Myokymia is thought to result from hyperexcitability of the lower motoneuron, and indeed both KCNQ2 and KCNQ3 mRNAs were detected in the anterior horn of the spinal cord where the cells of the lower motoneurons arise. We propose that a difference in firing patterns between motoneurons and central neurons, combined with the drastically slowed voltage activation of the R207W mutant, explains why this particular KCNQ2 mutant causes myokymia in addition to BFNC.

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Proximal myotonic myopathy/myotonic dystrophy type 2 (PROMM/DM 2) is caused by an expansion of the (TG)n(TCTG)n(CCTG)n repeat tract in intron 1 of the ZNF9 gene located on chromosome 3q21. Because these expansions show a marked mitotic instability, expanded alleles are often difficult to detect. In order to improve the diagnostic procedure, we applied a combination of pulsed-field gel electrophoresis and semi-quantitative Southern blot analysis with a novel hybridization probe. The combination of these methods led to unequivocal results in about 98% of cases with a clinical diagnosis of PROMM/DM 2. Furthermore, we report the genotype/phenotype correlation in a patient lacking a normal ZNF9 allele and a further proband with a "grey zone" allele.

Diagnosis, long-term management and family investigations of Wilson’s disease are provided by selected clinical institutions in the GDR. From 187 patients detected since 1949, 111 are alive. In spite of the principal effectiveness of penicillamine treatment, confirmed by the disappearance of most of the central nervous system symptoms and successful professional rehabilitation of many patients, insufficient therapeutic discipline, psychosocial disturbances and penicillamine side-effects forcing its substitution by zinc or triethylenetetramine dihydrochloride in 14 cases need our further attention.