Which histologic findings are characteristic of severe combined immunodeficiency (SCID)?

Updated: Apr 28, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Harumi Jyonouchi, MD  more...
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Answer

In classic SCID, the thymus is small with few thymocytes, and it lacks corticomedullary distinction and Hassall corpuscles (see the image below). The epithelium is normal.

Histologically, the thymus in severe combined immu Histologically, the thymus in severe combined immunodeficiency usually lacks Hassall corpuscles and is depleted of lymphocytes. In this photo, a Hassall corpuscle is identified to the right of center.

The skin and gut may show infiltration with histiocytes, eosinophils, or activated dysfunctional T cells. The epidermis can have foci of hyperkeratosis with parakeratosis or irregular acanthosis with spongiosis and exocytosis. The papular dermis has edema and a diffuse perivascular infiltrate with some eosinophils.

The spleen and peripheral lymph nodes are characteristically atrophic, but, in maternal and transfusion-mediated graft-versus-host disease (GVHD) or in Omenn syndrome, they may be hyperplastic, with histiocytes and eosinophils. The spleen is depleted of lymphocytes. Although a lymph node biopsy is not necessary for diagnosis, findings may indicate a paucity of T and B cells and a lack of germinal centers. The tonsils, adenoids, and Peyer patches are underdeveloped or absent.

Hemophagocytic lymphohistiocytosis is reported in XL-SCID and cartilage-hair hypoplasia.


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