Amyotonia Congenita

Much uncertainty exists as to what Oppenheim (1900) had in mind and what this entity is--if indeed it exists at all. See discussion by Greenfield et al. (1958) under the heading of 'the floppy infant.' When the primary defect resides in the spinal cord, the condition is infantile muscular atrophy (SMA1; 253300), otherwise known as Werdnig-Hoffmann disease or infantile spinal amyotrophy. Possibly the term amyotonia congenita should be reserved for those conditions in which the primary abnormality resides in muscle and the disorder is essentially nonprogressive. Certainly there are multiple causes, e.g., glycogen storage diseases, the atonic-astatic syndrome of Foerster (209100), and the congenital nonprogressive myopathy described by Batten and by Turner (255300). Nemaline myopathy (161800, 256030) and central core disease (117000) are other entities producing floppy infants.

Sarnat and Menkes (2006) stated that 'Oppenheim's poorly described patients with amyotonia congenita, a now obsolete term, would likely belong to the previously described category of 'benign congenital hypotonia' denoting 'an infant with hypotonia and mild, nonprogressive weakness who either improved with maturation or at least held his own.'