Cold agglutinin disease (CAD) can present as black fingertips and dark urine, according to a new case report published in QJM: An International Journal of Medicine.

The case involved a previously healthy 55-year-old woman who was found to have digital gangrene, elevated cold agglutinin titer, and a monoclonal immunoglobulin M-kappa protein without MYD88 L265P mutation, leading to the diagnosis of CAD.

“Digital gangrene often occurs in autoimmune diseases, Buerger’s disease, and arteriosclerosis obliterans,” the authors wrote. “In addition, [CAD] may also be a rare cause of digital gangrene. In this case, the onset of the digital gangrene and dark urine after cold exposure led us to suspect a [CAD].”


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The woman consulted the emergency department during the wintertime due to black urine and painful black coloration of 3 fingers. Initially, the cause was unknown, but laboratory examinations revealed possible hemoglobinuria, positive anti-C2b/C3d antibody, and negative anti-immunoglobulin G antibody.

The gangrene combined with the dark urine and identification of the monoclonal immunoglobulin M-kappa protein without MYD88 L265P mutation enabled a diagnosis of CAD, and she was successfully treated with debridement and 4 rounds of bendamustine and rituximab. The following winter, she had no further gangrene in her fingers nor any hemolytic attack.

Reference

Oda N, Rokutanda R, Terao T, et al. Black fingers & dark urine: cold agglutinin disease. QJM. Published online April 6, 2022. doi:10.1093/qjmed/hcac095