Can autoimmune thyroid disease coexist with autoimmune neutropenia?

Autoimmune thyroid disease (AITD) frequently co-occurs with other autoimmune conditions, including autoimmune neutropenia (AIN), due to a shared loss of immune tolerance and overlapping immunologic pathways.

Clinical evidence

The coexistence of AITD and AIN is well-documented in clinical research. Retrospective studies indicate that a substantial percentage of patients with neutropenia—ranging up to 43.6% in some cohorts—also present with underlying thyroid disorders. Specifically, Hashimoto's thyroiditis has been identified in approximately 23.4% of neutropenic patients. In untreated Graves' disease, the prevalence of mild to moderate neutropenia is nearly 30%, with the severity of the neutropenia often correlating with the degree of thyrotoxicosis (e.g., higher free T4 levels). While drug-induced agranulocytosis from antithyroid medications is a known risk, a subset of patients (~5%) experience neutropenia as a direct manifestation of their primary autoimmune state.

Mechanistic explanations

The reduction in circulating neutrophils in the context of thyroid autoimmunity is driven by two primary immune mechanisms:

• Peripheral Destruction: The presence of antineutrophil antibodies is a key driver. These antibodies opsonize circulating neutrophils, leading to their premature removal by the spleen and the reticuloendothelial system. Bone marrow biopsies in these patients often show active hematopoiesis without dysplasia, confirming that the loss occurs in the periphery.
• Suppression of Production: Although less common than peripheral destruction, immune mechanisms may also target myeloid precursors in the bone marrow. Antineutrophil antibodies can theoretically interfere with neutrophil maturation, and altered lymphocyte subsets (such as changes in CD4+ percentages) observed in Hashimoto's thyroiditis may disrupt the cytokine environment necessary for effective granulopoiesis.
• Inflammatory Feedback: Neutrophils in AITD patients may undergo increased NETosis (neutrophil extracellular traps), which can further stimulate the production of autoantibodies, creating a cycle of chronic inflammation and neutrophil depletion.

Bottom line

Autoimmune thyroid disease and autoimmune neutropenia frequently coexist through shared immune dysregulation. The resulting neutropenia is typically caused by antibody-mediated peripheral destruction or, more rarely, suppressed marrow production.