A profoundly prelingually deaf individual is someone who was born with insufficient hearing to acquire speech normally, or who lost their hearing prior to the age at which speech is acquired.
Also called "Prelingual hearing impairment", it exists when the impairment is congenital or otherwise acquired before the individual has acquired speech and language, thus rendering the disadvantages more difficult to treat because the child is unable to access audible /spoken communication from the outset. Prelingual deaf children born into signing families have no delay in language development and communication. Most pre-lingual hearing impairment is due to an acquired condition, usually either disease or trauma; therefore, families commonly have no prior knowledge of deafness.
In children, this type of hearing loss can lead to social isolation for several reasons. First, the child experiences delayed social development that is in large part tied to delayed language acquisition. It is also directly tied to their inability to pick up auditory social cues. This can result in a deaf person becoming generally irritable. A child who uses sign language, or identifies with the Deaf culture does not generally experience this isolation, particularly if he/she attends a school for the deaf, but may conversely experience isolation from his parents if they do not know, or make an effort to learn sign language. A child who is exclusively or predominantly oral (using speech for communication) can experience social isolation from his or her hearing peers, particularly if no one takes the time to explicitly teach them social skills that other children acquire independently by virtue of having normal hearing.