BROAD A-BAND DISEASE - A NEW, BENIGN CONGENITAL MYOPATHY

We report a second child with broad A band disease. This child differs from the first in having normal vision and no electrophysiological ev idence of a congenital retinal dystrophy. Neurological abnormalities a t presentation included diffuse hypotonia, developmental delay, and de layed speech development. Histological and preliminary histochemical e valuation of biopsied thigh muscle showed no abnormality. However, 1-m u m-thick plastic sections and electron microscopy showed numerous foc i of broadened A bands accompanied by loss of distinct I bands. The Z lines in these areas were normal except for a fine waviness. Ultrastru cturally, the thick filaments in these lesions appeared misaligned. Im munohistochemical reactions for desmin, vimentin, connectin (titin), a nd 2B myosin showed normal reactivity. An immunohistochemical reaction for fetal myosin showed sparse reacting fibers, which were unremarkab le on adjacent sections stained with hematoxylin and eosin. These find ings differ from those of other previously described congenital myopat hies. Both of our patients have shown good strength and motor developm ent by 5 years of age, suggesting that this ultrastructural abnormalit y is essentially benign. (C) 1996 John Wiley & Sons, Inc.