At this point, we are not in a position to propose an autoimmune
pathogenesis for delusional disorder and paranoid
schizophrenia. Although there are reports on the etiologic role
of several factors such as obstetric complications, low birth
weight, reduced head circumference, prenatal underdevelopment,
central nervous system damage, and maternal influenza
infections in schizophrenia (36), such studies have not yet
been conducted for delusional disorder. Our result is preliminary
and so far not correlated with parameters such as birth
status, viral infections, or prenatal infections. Nonetheless, we
can assume the possible existence of a susceptible locus
within the HLA region and that the HLA-A*03 gene may be
the sole determinant of delusional disorder. This significant
association may contribute to the disease risk, or else there
may be a separate susceptibility gene in strong linkage disequilibrium
with the A*03 gene.