This clinical presentation is consistent with hairy cell leukemia; first-line treatment for hairy cell leukemia consists of cladribine, an adenosine deaminase inhibitor.
Hairy cell leukemia is an uncommon chronic B cell lymphoproliferative disorder, which typically affects older adults, and is more common in men. Patients commonly present with symptoms related to massive splenomegaly and cytopenias. Diagnosis of hairy cell leukemia is made on the basis of several factors: recognition of the characteristic hairy leukocyte on blood smear with a “fried egg” appearance; bone marrow that cannot be aspirated due to extensive fibrosis; and a positive tartrate-resistant acid phosphatase (TRAP) assay. Treatment in hairy cell leukemia is indicated for alleviation of symptoms related to splenomegaly and cytopenias; cladribine is considered first-line therapy.
Summers and Jaffe discuss diagnostic criteria for hairy cell leukemia. They point out that certain features of the disease, such as the characteristic villous cytoplasmic projections may be seen in other B-cell lymphoproliferative disorders and are therefore not specific to hairy cell leukemia.
Dearden et al. report data on a 25-year retrospective review of 242 patients with hairy cell leukemia treated with either pentostatin or cladribine for a median follow-up of 16 years and find that there was no significant difference in outcome between the two agents as first or subsequent lines of therapy.
Figure A depicts a characteristic circulating hairy leukocyte from a peripheral blood smear. It is a mononuclear cell, usually one to two times the size of a mature lymphocyte, with a cytoplasmic outline that is often indistinct with varying projections. Illustration A shows a patient with massive splenomegaly, which is a common presenting sign in hairy cell leukemia.
Answers 1-3, 5: While these are all agents used in the treatment of various malignancies, they are not considered first-line therapy for hairy cell leukemia.
Summers TA, Jaffe ES. Hairy cell leukemia diagnostic criteria and differential diagnosis. Leuk Lymphoma. 2011 Jun;52 Suppl 2:6-10.
PMID:21417827 (Link to Abstract)
Dearden CE, Else M, Catovsky D. Long-term results for pentostatin and cladribine treatment of hairy cell leukemia. Leuk Lymphoma. 2011 Jun;52 Suppl 2:21-4.
PMID:21599603 (Link to Abstract)