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Reduced mucociliary clearance in primary ciliary dyskinesia (PCD) causes recurrent infections of the upper and lower respiratory tract. The disease is usually inherited as an autosomal recessive trait. To identify a gene locus for PCD, we studied a large consanguineous family of Arabic origin. Direct examination of the respiratory cilia revealed ciliary akinesia. Electron microscopic examination of cilia showed absence of the outer dynein arms. Two of four affected individuals exhibited a situs inversus, typical for Kartagener syndrome, due to randomization of the left/right body axis. A total genome scan with 340 highly polymorphic microsatellites was performed. We localized a new gene locus for PCD to a region of homozygosity by descent on chromosome 5p15-p14 with a parametric multipoint logarithm of odds ratio (LOD) score of Zmax = 3.51 flanked by markers D5S2095 and D5S502 within an interval of 20 centimorgans sex-averaged genetic distance. Applying a polymerase chain reaction-based approach, we identified a 1.5-kb partial complementary DNA of DNAH5 encoding a Chlamydomonas-related axonemal heavy dynein chain within the critical disease interval of this new PCD locus. On the basis of the Chlamydomonas model for PCD, this gene represents an excellent candidate for PCD.

Two affected siblings with infantile spinal muscular atrophy (SMA I) presented with generalized muscular hypotonia, which progressed to early death. Quadriceps muscle biopsy did not show the typical neurogenic pattern of spinal muscular atrophy. The histochemical fiber type determination revealed a predominance of type II fibers without type I hypertrophy, an unprecedented finding in spinal muscular atrophy. Sural nerve biopsy exhibited findings typical for axonal neuropathy. In one patient, electrical stimulation of peripheral nerves showed an inexcitability of motor and sensory nerves. Genetic studies revealed homozygous deletions of the telomeric survival motor neuron (SMN) gene and the neuronal apoptosis inhibitory protein (NAIP) gene in the affected children. This is the second case report of molecular genetically proven spinal muscular atrophy associated with axonal neuropathy. We conclude atypical findings on muscle biopsy and evidence of axonal neuropathy are compatible with the diagnosis of infantile spinal muscular atrophy.

Centronuclear myopathy (CNM) is a congenital myopathy which manifests itself as a severe neonatal (also termed myotubular myopathy), early-onset, or adult form. The histological pattern of each is marked by a considerable number of nuclei of muscle fibers being internally placed. Owing to their remote resemblance to myotubes, and their expression of developmentally regulated proteins, most authors now favor the concept that myogenesis is arrested or delayed in this disease. We here present two muscle biopsy specimens of a patient with early-onset CNM, taken at the age of 5 months and 14 years, respectively. The first biopsy sample contained internally placed nuclei in 7% of the muscle fibers, abundant minute myotubes, and hypertrophic muscle fibers. The second biopsy sample showed internally placed nuclei in 40% of the muscle fibers, and hypotrophic fibers. We suggest that the histological findings in early-onset CNM are the result of a complex dynamic process, which includes a delay in maturation.

Becker muscular dystrophy (BMD) was diagnosed in a male patient with Klinefelter's syndrome (47, XXY karyotype). The BMD was confirmed by (i) immunohistological methods and Western blotting, showing decreased quantity of dystrophin in muscle biopsy specimen and (ii) molecular genetic analysis which demonstrated a homozygous deletion of exons 45-47 within the dystrophin gene on both X-chromosomes. The same deletion was found on one of the X-chromosomes in the patient's mother. It can be deduced therefore that Klinefelter's syndrome in this patient is most likely due to a non-disjunctional error which occurred either during the second maternal meiotic division or during early postzygotic mitotic divisions.

A family with myoclonus epilepsy has been described previously as suffering from an X-linked disorder, because at least four males were affected, and only mild and variable symptoms were seen in some female carriers. In this family, we have now identified a mitochondrial A-->G (8344) heteroplasmic point mutation. This point mutation has been described in families with maternally inherited myoclonus epilepsy and ragged red fibers. The degree of severity of the disorder in the different family members was reflected in the relative quantity of mutated mitochondrial DNA. It is concluded that the mode of inheritance in this family is not X-linked but maternal.