Simultaneous Presentation of Cutaneous Waldenström Macroglobulinemia and Acalabrutinib-Related Toxicity.

Waldenström macroglobulinemia (WM) is a rare B-cell lymphoplasmacytic lymphoma associated with clonal IgM gammopathy, comprising 1%-2% of hematological malignancies. The clinical presentation exhibits diverse cutaneous manifestations, including paraproteinemia-related effects, autoimmune phenomena, and neoplastic cell infiltration. Next-generation Bruton tyrosine kinase inhibitors, such as zanubrutinib and acalabrutinib, have revolutionized WM treatment by enhancing selectivity but are associated with various dermatologic lesions. We report a case of a 74-year-old man with simultaneous presentation of cutaneous WM and an acalabrutinib-induced eruption. The drug reaction presented as blanching macules and papules, histologically showing superficial perivascular dermatitis and lymphocytic panniculitis with predominantly T cells. The cutaneous WM showed diffuse, dense dermal lymphocytic infiltrates, which were predominantly B cells. Recognizing these distinct histopathological patterns is crucial for accurate diagnosis and timely intervention. The evolving landscape of Bruton tyrosine kinase inhibitors necessitates vigilant clinical awareness of the delicate balance between harnessing therapeutic benefits and managing associated cutaneous complexities in patients with WM. In addition, these patients are susceptible to opportunistic infections. Awareness of the various cutaneous reactions and vigilant monitoring are required.