Does a single nucleotide change in a gene cause the observed internal deletion of 191 nucleotides in the mRNA ?

Protein P is predicted to be responsible for disease D. It is inactive in people with disease D, but active in normal people. What happens is that the mRNA transcribed from gene P (the gene that encodes protein P) isolated from individuals with disease was found to lack an internal stretch of 191 nucleotides that are present in the normal mRNA from healthy people.

The corresponding genes from the healthy and unhealthy person were sequenced, and the comparison of the DNA sequences shows that they differ by just one nucleotide, and no nucleotide insertion or deletion. How can I hypothesize a molecular mechanism by which a single nucleotide change in a gene could cause the observed internal deletion of 191 nucleotides in the mRNA? And what consequences for the protein P would result from removing the internal stretch of 191 nucleotides?