The hypodermis is the innermost and thickest layer of the skin. It invaginates into the dermis and is attached to the latter, immediately above it, by collagen and elastin fibres. It is essentially composed of a type of cells specialised in accumulating and storing fats, known as adipocytes.
Fatal familial insomnia Fatal familial insomnia (FFI) is a very rare, autosomal dominant inherited, disease of the brain. It is caused by a mutation in a protein called prion protein (PrP): asparagine-178 is replaced by aspartic acid.
Typically the sleep study, or polysomnogram, for fatal familial insomnia will demonstrate an absence of slow-wave sleep. In addition, there will be decreased amounts of stage 2 NREM sleep. Finally, there is dissociated REM sleep without loss of muscle tone.