Antibodies against HF persist after cure, and although specific antibody isotypes and sub-isotypes against HF, including IgE, IgM, IgG2 and IgG4, have been suggested to be of use for follow-up by several authors, the demonstration of usefulness of serology has been hampered by the low number of tested samples in published work and the lack of these antibodies in a percentage of patients with CE (rev. Here, IGHE is linked to hydrops fetalis.