To summarize expression profiling results we generated a heat map by using the average linkage method for all differentially expressed genes of seven CF patients and three non-CF control subjects (Figure 5). Interestingly it was detected that there was a strong correlation between non-CF control subjects and patients with Class IV mutation. Also the similarity of expression results between intermadiate (F3-P2) and severe (F3-P3) patients with Class IV mutation was prominent. The common genes were associated with hepatic involvement. It was concluded that the severity of hepatic involvement was similar between mild and severe patients with Class IV mutation and pathways involved in inflammatory response and protein processing may explain the clinical severity difference between these siblings. Another significant finding was the close correlation established between mild F1-P1 and severe F1-P2 siblings in Family 1. The common genes between F1-P1 and F1-P2 were found to have a role in LPS response, cytokine/chemokine activity and protein binding processes. Also, the upregulated genes in F1-P2, showed a positive correlation with hepatic involvement.