Three unrelated young children are reported to have suffered since birth from muscle
hypotonia and two of them from fatal respiratory insufficiency. Muscle tissues were found to
contain large masses of thin myofilaments, immunologically identified as containing actin,
but without further morphological features. These masses of thin filaments were found in
different muscles at different occasions in the three children, suggesting a disease-specific
morphological and possibly nosological feature all of them justifying classification as …