Clinical significance of acquired loss of the X chromosome in bone marrow

• Is a rare finding and only detected in women.
• Usually presents as a minor clone and is likely age-related or a benign finding.
• Could be associated with myeloid neoplasms when it presents as a major clone.

Acquired loss of the X chromosome (-X) as a sole abnormality is detected rarely in bone marrow (BM) and its clinical importance remains largely unknown. We studied 38 patients with isolated -X in BM. All patients were women, with a median age of 71 years. At the time of -X detection, BM was positive for myeloid neoplasm in 14 patients, lymphoma/myeloma in 10 patients, and was normal in 14 patients. -X was detected as a major clone in 15 patients (11 of them had myeloid neoplasm) and a minor clone in 23 patients. Combined morphologic and FISH analysis was performed in 16 cases, -X was detected in myeloid/erythroid cells in all 16 patients and in lymphocytes in 15 patients. With a median of 23 months follow-up, none of the patients with a negative BM or BM with involvement by lymphoid neoplasms developed a secondary myeloid neoplasm. We conclude that isolated -X is a rare finding in BM. In majority of patients, -X presents as a minor clone and is likely to be an aging effect or a benign finding; whereas when -X presents as a major clone in BM, it is often disease associated.