Autoimmune thyroiditis following HLA‐matched sibling hematopoietic stem cell transplantation for Wiskott‐Aldrich syndrome

WAS is a fatal X‐linked combined immunodeficiency syndrome, the only cures for which are HSCT or gene therapy. AID occur in up to 72% of patients with WAS who do not receive HSCT, likely arising secondary to impaired multilineage immune autoregulatory function; AITD is not typically seen. In this article, we describe the case of a male patient who underwent HLA‐matched HSCT for WAS at the age of 5 months, with his sister (a WAS carrier) acting as his donor and subsequently developed AITD 12 months post‐transplant, with marked elevation of antithyroid peroxidase antibody titer. His donor sister was subsequently found to have elevated antithyroid peroxidase antibody titer with increasing trend and normal thyroid function. Although several mechanisms exist by which our patient may have developed AITD, we suggest the transfer of autoreactive donor immune cells as the most plausible explanation.