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].”
Read more about CAD etiology
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.
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