Iminoglycinuria is a metabolic disorder resulting from defective renal tube reabsorption of proline, hydroxyproline and glycine. The prevalence is estimated at around 1 in 15 000. The disorder is usually asymptomatic and is identified fortuitously by detection of increased levels of the imino acids and glycine in the urine. It is transmitted as an autosomal recessive trait.

Muscular hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle), often involving reduced muscle strength. Hypotonia is characterized by a diminished resistance to passive stretching.