A study by Swedish scientists has suggested that severe pneumococcal disease requiring hospitalisation – most commonly pneumonia – can be a sign of previously undiagnosed blood cancer and immunodeficiency in adult patients.
The team from the University of Gothenburg followed 156 individuals who developed invasive pneumococcal disease and required hospital care in the Region Västra Götaland, Sweden, between 2018 and 2023, in the study published in the journal Nature: Scientific Reports.
The median age of the patients was 70.
The researchers examined their immune systems 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 people matched for age and sex who did not have invasive pneumococcal disease.
In the pneumococcal disease group, one in four 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 12 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 suggest that screening for M proteins and antibody levels in adults with invasive pneumococcal disease should be considered, 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,” said 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 programme.
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, she pointed out.
“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,” she added.
Study details
Invasive pneumococcal disease unmasks monoclonal immunoglobulins and antibody deficiencies: a multicentre prospective study in adults
Tor Härnqvist, Karin Bergman, Åsa Mellgren et al.
Published in Nature Scientific Reports on 24 July 2026
Abstract
Immunoglobulins (Ig) are essential for protection against invading pneumococci but are not routinely analysed in patients with invasive pneumococcal disease (IPD). In this prospective study, we assessed the prevalence of monoclonal Ig (M protein) and analysed Ig concentrations in sera from 156 adult IPD patients (median age 70 years). Patients were sampled during acute infection (n = 153) and in the convalescence phase 2-4 months after acute infection (n = 76). Sixty-four sex- and age-matched individuals without IPD served as controls. During infection, M protein was detected in 22% (31/141) of patients without previously known haematological malignancy as compared with 5% of the controls (p = 0.002). Seven of these patients were subsequently diagnosed with a haematological malignancy, including multiple myeloma, Waldenstrom macroglobulinemia, and mantle cell lymphoma. Another 12 patients were diagnosed with monoclonal gammopathy of undetermined significance (MGUS). Convalescence levels of IgA, IgG2, or IgG4 were below the reference intervals in 16–20% of patients and 0–2% of controls. Three patients were diagnosed with a primary Ig deficiency, and seven patients started Ig replacement therapy. Our findings suggest that assessment of M protein and Ig levels could be considered in adults with IPD, as an episode of IPD may unmask a previously undiagnosed B-cell malignancy or immunodeficiency.
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