Trisomy 10p and translocation of 10q to 4p associated with selective dysgenesis of IgA-producing cells in lymphoid tissue.

A combined chromosomal abberation trisomy of the short arm of chromosome 10 associated with translocation of 10q to chromosome 4p was found in a 14-month-old boy, who died after repeated bouts of pneumonia. The translocation involved the target region 4p16.3 of Wolf-Hirschhorn syndrome and/or Pitt-Rogers-Danks syndrome. The karyotype was 46,XY,der(4)t(4;10)(p16;q11.2),i(10)(p10),ish der(4)t(4;10)(p16.3;q11.2) (D4S96+,D4Z1+),i(10) (pter ++). In addition to growth retardation and external as well as internal dysmorphism, the patient had abnormalities of the immune system, such as thymic involution, generalized lymph node enlargement, unusual distribution of T cells in lymphoid follicles, and selective IgA deficiency. The IgA-producing cells were rarely found in lymph nodes but normally in intestinal mucosa. In contrast, in the lymph nodes, the paracortical T-lymphocytes were hyperplastic, but they rarely entered the primary follicles. It is assumed that the chromosomal abnormality may lead to the dysfunction of T lymphocytes and, further, to the dysgenesis of IgA-producing cells in lymph nodes but not in intestinal mucosa. This suggests that the thymus may differentially control the subsets of IgA-producing cells in lymph nodes and intestinal mucosa.