Pneumonia can reveal undiagnosed blood cancer, suggests study

Severe pneumococcal disease requiring hospitalization, most commonly pneumonia, can be a sign of previously undiagnosed blood cancer and immunodeficiency in adult patients, according to a study from the University of Gothenburg.

The study followed 156 individuals who developed invasive pneumococcal disease and required hospital care in the Region Västra Götaland between 2018 and 2023. The median age of the patients was 70 years.

The researchers examined the patients' immune system by measuring antibody levels and studied the presence of M protein, known as a risk marker for blood cancer. The control group consisted of 64 individuals matched for age and sex who did not have invasive pneumococcal disease.

In the pneumococcal disease group, one in four individuals had M protein in their blood, a marker that may be present in blood cancer or in precursor conditions. The examinations led to seven patients being diagnosed with blood cancer, while another twelve were diagnosed with a condition that can, in some cases, progress to blood cancer.

Routine screening should be considered

Eight patients were found to have immunodeficiency, seven of whom were able to start preventive treatment against new, severe infections. These findings were considerably less common in the control group.

The results, published in the journal Scientific Reports, suggest that screening for M proteins and antibody levels in adults with invasive pneumococcal disease should be considered, according to the researchers, as the disease can reveal previously undiagnosed blood cancer and immunodeficiency.

"Currently, these tests are not routinely performed after a severe pneumococcal infection. As a result, we may miss patients with undiagnosed blood cancer or immunodeficiency and therefore missing the opportunity to initiate treatment," says Tor Härnqvist, a doctoral student at the University of Gothenburg, an infectious disease physician at NU Hospital Group, and one of the lead authors.

Importance of tailoring vaccinations

Karin Bergman is a doctoral student in the same research group and an infectious disease physician at Södra Älvsborg Hospital. The study is part of her doctoral thesis, which she will soon defend at the University of Gothenburg, in which she also demonstrates how the pneumococcal bacteria causing severe disease have changed since the pneumococcal vaccine was introduced into the Swedish childhood vaccination program.

The bacterial serotypes covered by the childhood vaccine have decreased sharply but have largely been replaced by other serotypes against which the vaccine offers no protection. Older adults and individuals with underlying conditions, particularly cancer and compromised immune systems, are frequently affected by these serotypes.

"The results show that recommendations on pneumococcal vaccines for adults need to take into account which vaccines are used in children and which bacterial serotypes subsequently circulate in the community," says Karin Bergman.

Reference:

Härnqvist, T., Bergman, K., Mellgren, Å. et al. Invasive pneumococcal disease unmasks monoclonal immunoglobulins and antibody deficiencies: a multicenter prospective study in adults. Sci Rep 16, 23203 (2026). https://doi.org/10.1038/s41598-026-61992-8