As early as Pre-K and school age, communication disorder and learning disability seem to appear together almost all the time. However, this is a common misconception that stems from the simple fact that children do not have enough schema to build upon and understand the differences between one sound or another. If you cannot tell the difference between what a word you hear sounds like, and what the word is supposed to sound like, there is really not much a child that age can do.
However, although both conditions seem to manifest together keep in mind that the stemming factors of each are not the same.
While commo disorders develop from hearing and speech body malfunctions that result from developmental issues of the body, learning disorders stem from cognitive issues such as dyslexia, or pervasive developmental disorder, to cite two examples.
Therefore, the two conditions may co-exist and feed off each other, but we have to be careful not to use the terms "learning disability" and "learning gap" interchangeably. When commo issues cause issues in learning, a gap occurs. When physical and cognitive delays appear then that is a disability.
This is how a gap forms and may be mistaken by disability: if a student comes in with a communication disorder, such as stuttering, or those commo disorders often associated with chronic ear infection that leads to partial deafness, a learning gap comes when it is time to introduce the student to basic phonics, to new vocabulary, repetition, songs, poems and sentences.
All of these are beginning interventions for pre-reading. A child that cannot produce these building blocks of literacy will undoubtedly fall behind his or her peers. That is still gap, and not disability.
However, in these cases what happens always (except in exceptionally rare cases) is that the student is immediately referred to immediately remedy the situation and place the child back to the mainstream classroom immediately after. The job of the SLP is to intervene right after the hearing issue is addressed, and work together with the GenEd teacher to plan catch-up interventions. If the hearing problem goes unnoticed for whatever reason (parent negligence, lack of services, misplacement of federal ADA funding) the gaps become wider and more dangerous for the student.
Hence, it is more accurate to say that one condition may appear as a consequence of the other if an intervention is not implemented as soon as possible.