The case of an adolescent with idiopathic recurrent myoglobinuria is reported. The following features are emphasized: (1) persistence of limb weakness and elevated CK levels between the attacks, (2) a constant myopathic pattern in EMG, and (3) chronic morphologic abnormalities of myopathy in two muscle biopsies. All known causes of myoglobinuria were investigated and ruled out.

Tassin S. & Brucher J. M. 1982 Neuropathology and Applied Neurobiology 8, 251–263Annotation. The mitochondrial disorders: pathogenesis and aetiological classificationMitochondrial myopathies form a heterogeneous group of muscular diseases characterized by the presence of morphological mitochondrial abnormalities. These abnormalities are interpreted as the stereotyped morphological expression of a cellular energy deficiency. They represent a compensatory mechanism destined to increase ATP production. On this pathogenetic basis, an aetiological classification for the mitochondrial myopathies is proposed. The consequences of this hypothesis on the meaning of the morphological abnormalities, notably the changes in the amount of glycogen and lipids associated with mitochondrial alterations, are analysed.

The authors present and illustrate most of the ultrastructural abnormalities encountered in skeletal muscle in cases of neuromuscular disease. The diagnostic significance of the changes are discussed but emphasis is laid on the nonspecific character of most of them. For diagnostic purposes, examination by light microscopy remains the preferred approach, but electron microscopy enables the nature and origins of the lesions to be better defined and is a very valuable technique in exploring the pathogenesis of muscular diseases.

Mitochondrial myoencephalopathies might be defined as diseases with mitochondrial alterations in skeletal muscle and brain, often combined with mitochondrial alterations in other organs. Examples are Reye’s syndrome (8, 9) kinky hair syndrome (3, 4) and Zellweger’s syndrome (5, 6).

A case of Waldenström's disease with peripheral nerve involvement resembling mononeuritis multiplex is described. The various etiopathogenic mechanisms generally cited in connection with peripheral neuropathies observed in cases of macroglobulinemia, most often of the polyneuritic type, are discussed in turn : nerve infiltration by lymphocytes, intervention of an immunologic mechanism through the agency of paraprotein links with amyloidosis. However, the reported case differs from habitual cases on account of the asymmetry of the nerve involvement and the discovery of vasculitic lesions on muscle biopsy. The hypothesis of ischemic neuropathy associated with serum hyperviscosity is proposed and confirmed by the clinical improvement and reduction of macroglobulin obtained by repeated plasma exchanges and administration of Chlorambucil.

Tassin S., Walter G.F., Brucher J.M. & Rousseau J.J. (1980) Neuropathology and Applied Neurobiology 6, 337–347.Histochemical and ultrastructural analysis of the mitochondrial changes in a familial mitochondrial myopathyTwo familial cases of progressive external ophthalmoplegia with involvement of pharyngeal and distal muscles are presented. ‘Ragged‐red’ fibres were found in both cases. Excessive amounts of RNA, as evidenced by the acridine orange‐induced fluorescence, were noted in many muscle fibres, mostly in the ‘ragged‐red’ fibres. At the ultrastructural level, numerous mitochondrial changes with paracrystalline formations were noted. Those formations were observed in three forms and a three‐dimensional reconstruction is proposed which suggests that the paracrystalline formations consist of undulating parallel leaflets joined along the top of the undulations. Small transverse bridges between neighbouring cristae and between cristae and paracrystalline formations are also emphasized. All those mitochondrial abnormalities are thought to represent the morphological expression of a biochemical deficiency in the inner membrane. They are interpreted thus: firstly, the biochemical defect leads to a multiplication of the mitochondria with increase in their volume and proliferation of the cristae in order to improve energy production; secondly, bridges between the modified inner membranes induce attachment of the neighbouring cristae and result in paracrystalline formations.