Welander distal myopathy--an overview.

Welander distal myopathy has an autosomal dominant inheritance and a late onset. The onset of symptoms is in the hands and gradually distal muscles of the lower extremities are involved. The most-affected muscles are the long extensors of the hands and feet. CK-values are normal or slightly elevated. There is never any cardiac involvement in Welander distal myopathy. Neurophysiological findings are of both myopathic and neuropathic character. Histopathological findings in muscle biopsies are mainly of myopathic type and include rimmed vacuoles which correspond to autophagic vacuoles on the ultrastructural level. Tubulo-filamentous inclusions with a diameter of 16-21 nm, i.e. of the same type as found in patients with Inclusion Body Myositis, are found in the sarcoplasm and in myofibre nuclei. A neurogenic component in Welander distal myopathy has been suggested, on the grounds of a sensory dysfunction, neuropathic findings on neurophysiology and muscle biopsy and a decrease of A-delta nerve fibres on sural nerve biopsy. Genetic analysis has excluded linkage to other defined distal myopathies and hereditary Inclusion Body Myopathy loci.