# Pure White Cell Aplasia, an Exceedingly Rare Complication of a Thymoma, and Immune Reconstitution Following Bone Marrow Recovery

## TL;DR

This paper reports a rare case of white blood cell deficiency caused by a thymoma and discusses immune recovery after bone marrow treatment.

## Contribution

The paper presents a novel case of thymoma-associated pure white cell aplasia and its immune reconstitution following marrow recovery.

## Key findings

- Thymoma-associated PWCA is exceedingly rare with few reported cases.
- Immune reconstitution occurred following marrow recovery in this patient.
- Post-mortem findings confirmed granulocytic hyperplasia in the bone marrow.

## Abstract

Background: Thymoma-associated pure white cell aplasia (PWCA), characterized by agranulocytosis with absent myeloid precursors in the bone marrow in the setting of preserved erythropoiesis and megakaryopoiesis, is exceedingly rare, with only a few cases reported in the literature. We present a case of type-B2-thymoma-associated PWCA and immune reconstitution following marrow recovery. Case Presentation: A 75-year-old woman was incidentally found to have a concomitant mediastinal mass and peripheral leukopenia with absent granulocytes and monocytes. Bone marrow assessment was notable for a hypocellular marrow (<10%) with absent granulopoiesis and monopoiesis. Chest CT demonstrated a large lobulated anterior mediastinal mass, for which the patient underwent a video-assisted thoracoscopic thymectomy. Pathological evaluation of the mediastinal mass specimen revealed a type B2 thymoma. A tentative diagnosis of thymoma-associated PWCA was made, and the patient was started on cyclosporine/granulocyte-colony stimulating factor (G-CSF)/filgrastim therapy. Despite promising marrow recovery, she developed several comorbidities and had a leukemoid reaction, provoking concern for immune reconstitution following prolonged neutropenia and subsequent treatment. She passed away on post-operative day 15, and the results of a post-mortem bone marrow examination were consistent with granulocytic hyperplasia. Conclusions: This case of thymoma-associated PWCA heightens awareness regarding this entity, providing a note of caution regarding the possibility of immune reconstitution following treatment and marrow recovery.