No abstract

Skin testing with mumps virus antigen solution was performed in 50 children with clinically diagnosed primary E.F.E. (Group I), and in 202 children who served as a control group (Group II). A further group of children with congenital mitral insufficiency (Group III) were similarly skin tested. Approximately 91% of the children with clinical E.F.E. under the age of 2 years in Group I showed a "positive" reaction to the intradermal inoculation of mumps skin-test antigen solution. In contrast, approximately 91% of the children in a control series under the age of 2 years in Group II showed a negative skin reaction. Confirmatory evidence of E.F.E. was obtained by left atrial biopsy in 2 children in Group I and in three children with congenital mitral insufficiency (Group III). E.F.E. was confirmed at autopsy in a fourth child with clinically diagnosed congenital mitral insufficiency who had shown a "positive" skin reaction. Hematologic studies for determination of mumps serum antibody titer (M.S.A.T.) were performed on 24 children in Group I, 29 children in Group II, and 6 children in Group III. It was apparent from our study that "positivity" of the skin reaction in E.F.E. was not correlated with an elevated M.S.A.T. Isolated congenital mitral insufficiency is, almost invariably, associated with E.F.E. The high incidence of "positive" reactors in this group suggests that both conditions arise in utero at the same period of gestation and due to an identical etiologic agent (possibly viral) and associated with fetal immunologic deficiency. "Positivity" of the skin reaction in E.F.E. to mumps antigen solution may, therefore, represent either: (1) a non-specific hypersensitivity; or (2) "cross-reactivity" to viruses other than mumps virus, for example, Coxsackie B viruses or myxoviruses other than mumps virus; or (3) evidence of preexisting mumps viral infection in utero or during infancy, despite the absence of an elevated M.S.A.T. This is explicable on the basis of a partial immunologic deficiency whereby the fetus or infant is incapable of developing specific mumps antibodies, but remains capable of exhibiting a delayed cutaneous hypersensitivity response to mumps antigen. Such an immunologic deficiency could also explain the familial occurrence of E.F.E. It is hoped that this report will stimulate further studies in (1) the value of the mumps skin-test antigen solution as an ancillary aid in the diagnosis of E.F.E. and (2) the possible role of viral infection(s) in the etiology of E.F.E.