The floppy infant: recent advances in the understanding of disorders affecting the neuromuscular junction. The clinician is often asked to evaluate the floppy infant. Numerous conditions that cause hypotonia in infancy are briefly outlined in this article. These conditions may affect the brain, spinal cord, or motor unit. Several disorders of neuromuscular transmission, including four distinct and recently described congenital myasthenic syndromes and infant botulism, are discussed thereafter. 