There is no clear separation between noise and signal. Pfam:PF00053 is very similar, but has 8 instead of 6 conserved cysteines. Includes some cytokine receptors. The EGF domain misses the N-terminus regions of the Ca2+ binding EGF domains (this is the main reason of discrepancy between swiss-prot domain start/end and Pfam). The family is hard to model due to many similar but different sub-types of EGF domains. Pfam certainly misses a number of EGF domains.

1: Solution structure of a pair of calcium-binding epidermal growth factor-like domains: implications for the Marfan syndrome and other genetic disorders. Downing AK, Knott V, Werner JM, Cardy CM, Campbell ID, Handford PA; Cell 1996;85:597-605. PMID:8653794

2: Structure and distribution of modules in extracellular proteins. Bork P, Downing AK, Kieffer B, Campbell ID; Q Rev Biophys 1996;29:119-167. PMID:8870072