Journal of the Neurological Sciences, 1990, 96:211-228

211

Elsevier

JNS 03318

Myopathy with respiratory failure and typical myofibrillar lesions Lars EdstrOm, Lars-Eric Thornell, Jaan Albo, Sven Landin and Margareta Samuelsson Departments of Neurology, Karolinska Hospital and Danderyd Hospital, Stockholm (Sweden), Department of Anatomy, Umed University and Department of Neurology, Orebro Hospital, Une~ (Sweden) (Received 11 October, 1989) (Revised, received 28 December, 1989) (Accepted 28 December, 1989)

SUMMARY

16 patients representing 7 different pedigrees exhibited an unusual, adult onset limb-girdle myopathy with typical clinical hallmarks. In a majority of cases there was evidence of an autosomal dominant inheritance. A prominent early finding in all cases was respiratory muscle weakness, and in many of these an acute respiratory incapacity was the reason for the In'st neurological examination. Neck flexor and sometimes foot extensor weakness were other early symptoms. The clinical picture seems to be at variance with that of the more well known hereditary myopathies. Electrophysiological analysis confirmed a myopathy and serum muscle enzyme concentrations were normal or slightly elevated. Muscle biopsy findings revealed myofibrillar changes which, at the light microscopy level, included plaques that stained strongly with rhodamineconjugated phalloidin, a specific marker for F-actin. At the ultrastructural level, these plaques were observed to be composed of moderately dense, thin filaments and were related to splitting of Z-discs or formed extensions from Z-discs. We believe that the muscle biopsy changes revealed by cytochemical and ultrastructural observations indicate defective myofibrillogenesis, and the possibility of defective actin polymerization is discussed. A conclusive answer requires further immunocytochemical and immunoelectrophoretic studies and possibly the application of molecular genetics.

Correspondence to: Dr. Lars Edstr6m, Department of Neurology, Karolinska Hospital, S-104 01 Stockholm, Sweden. 0022-510X/90/$03.50 © 1990 Elsevier Science Publishers B.V. (Biomedical Division)

212 Key words: Myopathy; Muscle dystrophy; Respiratory failure; Respiratory muscles; Sarcomere; Z-disc; Actin; Rhodamine-phalloidin; Desmin

INTRODUCTION Serious respiratory failure as a prominent early symptom of a hereditary myopathy is uncommon, although many respiratory problems commonly accompany more advanced stages of muscle dystrophies, such as Duchennes disease and myotonic dystrophy. Disorders with early respiratory failure include late onset Pompes disease (acid maltase deficiency), in which one-third of the cases involve early respiratory failure (Rosenow and Engel 1978) and respiratory involvement may occur in all cases and is often a cause of death. In nemaline myopathies (Kuitonnen et al. 1972; Dubowitz 1978), fatal progressive respiratory failure is also frequently encountered in the first and second decade of life. Among the group of disorders exhibiting muscle fiber inclusions similar to the cytoplasmic bodies of Engel (1962), occasional cases with early respiratory failure are reported (Jerusalem et al. 1979; Patel et al. 1983; Banker 1986; Winter et al. 1986). The present paper reports 16 cases representing 7 families who exhibit a limbgirdle syndrome with neck flexor weakness and a prominent involvement of respiratory muscles. The disease may typically be inherited as an autosomal dominant trait. The muscle biopsy findings included various myopathic changes, and characteristic myofibrillar changes were found in all biopsies. At the light microscopy level, there were plaques of material in many fibres that exhibited strong fluorescence of rhodamine-conjugated phaUoidin, which selectively binds to F-actin. We conclude that all these cases represent one and the same disorder. A preliminary report has been published elsewhere (EdstrOm and Thornell 1986).

MATERIALSAND METHODS Most biopsies were taken from the vastus lateralis of the quadriceps (VL) or the anterior tibial muscle (TA), but occasionally from the deltoid muscle (cf. Table 1). Most biopsies were obtained by means of a percutaneous modified Radner technique (Henriksson 1979), but some using open surgery.

Methodsfor specimenpreparation Specimens intended for ordinary light and fluorescence microscopy were frozen in Freon 13 cooled by liquid nitrogen (at - 190 °C) and kept in a refrigerator (at 75 °C) until 4-10 #m thick sections were cut in a cryostat at - 25 °C. Specimens intended for transmission electron microscopy (TEM) were pinned between needles on a piece of cork and fixed in 2.5~o gluthar aldehyde in phosphate buffer. Proceduresfor light microscopy. Stainings for hematoxylin-eosin and trichrome modified according to Engel and Cunningham (1963) were employed as well as histo-

213 chemical stainings for myosin-adenosine triphosphatase (myosin-ATPase) with alkaline and acid preincubations, NADH-TR, succinic dehydrogenase, fat, glycogen and acid phosphatase (cf. Dubowitz 1985). For visualization of F-actin in fluorescence microscopy, we used rhodamineconjugated phalloidin, which binds selectively to polymerized actin filaments (Molecular Probes Inc., Junction City, Oregon, U.S.A.). For visualization of the intermediate filament subunit desmin, we used a well characterized monoclonal antibody whose specificity has been described previously (Virtanen et al. 1986). The antibody was identified under fluorescence microscopy after labelling with a secondary FITC-conjugated rabbit anti-mouse serum. Procedures for transmission electron microscopy. After fLxation,the samples were washed in buffer and cut into blocks approximately 2 x 0.5 ram, postfixed in OsO 4 in PBS, dehydrated in acetone and embedded in Vestopal or Epon. 1.0-0.5-#m thick sections were cut on an LKB ultratome IV and stained with toluidine blue for light microscopy. After identification of areas of interest, ultrathin sections were produced and stained with uranyl acetate and lead citrate and examined in a Philips 300 or a JEOL 1200EX electron microscope.

RESULTS

Clinical hallmarks A summary of clinical and laboratory findings is presented in Table 1. Pedigree maps of three families presenting several members with typical symptoms are displayed in Fig. la-c. All cases were characterized by a proximal muscle weakness of the upper and lower extremities, with early affection of neck flexors and respiratory muscles, especially the diaphragm. There was sometimes an early involvement of dorsal foot extensors. Other distal muscles were spared for the most part but fmger extensors were involved in 4 cases. Cranial nerve innervated muscles were mostly spared, except for the sternocleidomastoid. In one patient there was, however, a bilateral weakness of the eye bulb abductors since early childhood and in one patient a slight myopathic face was observed. Muscle reflexes were normal or decreased but never totally inhibited. Time of onset varied from between the second and fifth decade. It must, however, be emphasized that the time of onset of some minor neuromuscular deficits is very difficult to establish. A majority of the patients admitted weakness of neck flexor muscles since early childhood on specific inquiry. The course of the disease seemed to be slowly progressive. No affection of the central nervous system or the sensory peripheral pathways has been observed, and no clear-cut clinical signs of cardiomyopathy were found.

Laboratory findings Electromyography (EMG) revealed a myopathy in all cases, but in one patient occasional muscles exhibited a mixture of neurogenic and myogenic changes. Peripheral

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