Broad A band disease: A new, benign congenital myopathy

Abstract

We report a second child with broad A band disease. This child differs from the first in having normal vision and no electrophysiological evidence of a congenital retinal dystrophy. Neurological abnormalities at presentation included diffuse hypotonia, developmental delay, and delayed speech development. Histological and preliminary histochemical evaluation of biopsied thigh muscle showed no abnormality. However, 1‐μm‐thick plastic sections and electron microscopy showed numerous foci of broadened A bands accompanied by loss of distinct I bands. The Z lines in these areas were normal except for a fine waviness. Ultrastructurally, the thick filaments in these lesions appeared misaligned. Immunohistochemical reactions for desmin, vimentin, connectin (titin), and 2B myosin showed normal reactivity. An immunohistochemical reaction for fetal myosin showed sparse reacting fibers, which were unremarkable on adjacent sections stained with hematoxylin and eosin. These findings differ from those of other previously described congenital myopathies. Both of our patients have shown good strength and motor development by 5 years of age, suggesting that this ultrastructural abnormality is essentially benign. © 1996 John Wiley & Sons, Inc.

Congenital myopathies at their molecular dawning

“…Most await confirmation by independent researchers. Their common denominator are myopathological features considered pathognomonic for the respective CM, implying Aband 135,136 inclusions. 20,137,205 A group of several patients has been carved out among a large series whose biopsied muscle specimens showed a considerable preponderance of trabecular/lobulated fibers suggesting a separate type of myopathy.…”

“…Their classification and characterization have addressed their frequency as "classic," "accepted," and "doubtful" conditions 66,72 based on the type of structural lesions. 64,66,78 Al-though some 40 entities are reported, some of these, such as "A-band disease" 135,136 or "cap disease," have been described only by one group of authors without confirmation by others, and are still awaiting independent corroborating observation. CM are exclusive muscle diseases, and the heart may be affected occasionally, as in nemaline myopathy and desminrelated myopathies.…”

Disturbance of muscle fiber differentiation in congenital hypomyelinating neuropathy caused by a novel myelin protein zero mutation

“…Ultrastructural analysis showed streaming of the Z and A bands and disruption of the sarcomeres (see Fig 1C, D). The pathology was suggestive of broad A‐band myopathy 11…”