Hairy cell leukemia C91.40

Low-malignant lymphocytic non-Hodgkin's lymphoma of the B-cell type, which shows atypical B-lymphocytes with hair-like extensions, cytochemical evidence of the tartrate-resistant acid phosphatase reaction and mature B-cell markers (CD11c, CD103, CD25) in the blood smear (see also lymphoma, cutaneous B-cell lymphoma).

The disease is probably caused by a mutation in the BRAF gene (V600E).

Median age of onset: 60 years; m:f=4:1

Slowly progressive disease with swelling of the lymph nodes, enlargement of the spleen or liver, anaemia.

Skin and hairy cell leukaemia: Very rare are specific skin manifestations in the form of solitary or multiple, red to red-brown papules and nodules with a smooth surface (Fino P et al. 2012). Furthermore, (non-specific) skin manifestations have been described that develop in the wake of the persistent and progressive immune insufficiency of this patient group:

• Sweet syndrome (Alkayem M et al. 2014).
• Vasculitic syndromes such as: leukocytoclastic vasculitis, panarteritis nodosa.
• Behcet's type skin and mucosal lesions (Oksuz MF et al 2014).
• Tendency to occur UAW (especially arceimite exanthema) especially after chemotherapy (Ganzel C et al. 2012).
• Panniculitides
• Increased occurrence of "banal" but also serious bacterial and viral infections of the skin (Robak E et al. 2021)

Pancytopenia, monocytopenia, in peripheral blood smear: hair cells!

Immunophenotyping: positivity for CD11c, CD15, CD103, CD123

Bone marrow: positivity for CD20, tartrate-resistant acid phosphatase (TRAP), CD72, Annexin A1

Treatment of the underlying disease. If BRAF V600E mutation is detected Therapy with Vemurafenib

Depending on the stage; complete remission can be achieved. Infections are the most frequent cause of death.

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2. Alkayem M et al (2014) A case report of hairy cell leukemia presenting concomitantly with sweet syndrome. Case Rep Med doi: 10.1155/2014/823286.
3. Chubar Y et al (2003) Cutaneous reactions in hairy cell leukaemia treated with 2-chlorodeoxyadenosine and allopurinol. Br J Haematol 122: 768-770
4. Fino P et al (2012) Skin metastasis in patient with hairy cell leukemia: case report and review of literature. In Vivo 26:311-314
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10. Oksuz MF et al (2014) Hairy cell leukemia presenting initially with symptoms of Behçet's disease. Int J Rheum Dis 17:689-692
11. Robak E et al (2021) Skin changes in hairy cell leukemia. Ann Hematol 100: 615-625.