Literature
Clinical Pearls & Morning Reports
Published November 6, 2024
Hairy-cell leukemia is associated with opportunistic infections. Read the NEJM Clinical Problem-Solving Article here.
Clinical Pearls
Q: Describe the triad of findings that is suggestive of hairy-cell leukemia.
A: Hairy-cell leukemia, originally termed leukemia reticuloendotheliosis, is a chronic, usually indolent, B-cell cancer expressing CD25, CD103, and CD11c. Hairy-cell leukemia typically manifests with a triad of pancytopenia, splenomegaly, and a “dry” bone marrow aspirate (attributed to fibrosis elicited by neoplastic cells) and is associated with monocytopenia.
Q: When is a diagnosis of hairy-cell leukemia variant more likely than hairy-cell leukemia?
A: The diagnosis of hairy-cell leukemia variant is considered in the presence of nonmutated BRAF status, leukocytosis, the presence of a prominent nucleolus in the hairy cells, extramedullary involvement, or absent CD25 or annexin A1 expression. Hairy-cell leukemia variant is more aggressive and responds less well to the monotherapy that is often used for hairy-cell leukemia.
A: In contrast to other chronic B-cell cancers, hairy-cell leukemia is notable for prolonged remissions with single-agent chemotherapy. Standard care remains cladribine for 5 to 7 days, which is repeated if clinical relapse occurs. In a prospective observational study approximately 90% of patients had a complete response to cladribine, although relapse was reported to occur in approximately 40% of patients over a median follow-up of 9 years. Most patients have a response to repeated courses of cladribine therapy. Splenectomy was the first treatment for hairy-cell leukemia but is now rarely used. Combination therapy with cladribine plus the anti-CD20 agent rituximab is increasingly used. Treatment options recently broadened with the introduction of the BRAF inhibitor vemurafenib. More than 95% of cases of hairy-cell leukemia include a BRAF V600E mutation, which results in constitutive activation of a kinase signaling cascade and promotes leukemic transformation. Treatment is not necessarily warranted in all patients with hairy-cell leukemia.
A: Hairy-cell leukemia is associated with an increased risk of disseminated infections, which has been attributed to reductions in monocytes, dendritic cells, and natural killer cells due to bone marrow fibrosis. Nontuberculous mycobacterial infections are reported in 5 to 10% of patients with hairy-cell leukemia. M. chimaera is a slow-growing, ubiquitous nontuberculous mycobacterium. Named in reference to a mythological creature composed of three animals (lion, goat, and snake), M. chimaera is a unique mycobacterial isolate containing elements of three other mycobacterial strains: M. avium, M. intracellulare, and M. scrofulaceum. M. chimaera infections occur more commonly in persons with immunocompromise than in those without immunocompromise and have been linked to natural water sources, water distribution systems in buildings, and contaminated water during extracorporeal circulation for cardiac surgery. In a case series of patients in whom disseminated M. chimaera infection developed after cardiac surgery, common symptoms included fever, malaise, weight loss, cough, and dyspnea; mortality was greater than 50% despite treatment.