Myofibers in tongues of Down's syndrome.

Muscle samples from the anterior part of the tongue in 15 patients with Down's syndrome (undergoing partial glossectomy), and 6 post-mortem controls, were examined histochemically. In most cases there was a Type 2 myofiber hypertrophy and preponderance, with frequent type 'grouplet' formation. In four cases examined ultrastructurally, hyperplastic, disorganized and atrophic neuromuscular junctions were seen. These preliminary ultrastructural findings suggest that synaptic morphometry could be a rewarding method of studying neuromuscular deficits in Down's syndrome.