TOPLINE

Invasive pneumococcal disease (IPD) revealed undiagnosed blood cancers and monoclonal gammopathy of undetermined significance (MGUS) in a considerable proportion of adult patients, a Swedish study found.

METHODOLOGY

• Researchers conducted a prospective multicentre study in Sweden between March 2018 and September 2023 to assess the prevalence of monoclonal immunoglobulin (Ig) called M protein and to measure Ig levels among patients with IPD.
• They enrolled 156 patients (median age, 70 years; 46% men) with pneumococcal infections confirmed by culture of blood or cerebrospinal fluid (CSF), or by polymerase chain reaction in CSF, along with 64 age- and sex-matched control individuals. Pneumonia was the most common manifestation (84%).
• Blood samples were collected during acute infection (n = 153) and at convalescence 2-4 months later (n = 76).
• Immunoglobulins (M protein, IgG, IgA, IgM, and IgG subclasses) were measured using immunoassay and electrophoresis, and lymphocyte populations (CD3+ T cells, CD3+CD4+ helper T cells, CD3+CD8+ cytotoxic T cells, and CD19+ B cells) were analysed using flow cytometry in samples in the convalescent phase.

TAKEAWAY

• After adjustment for age, sex, and predisposing conditions, patients with IPD had significantly eightfold higher odds of M protein detection than non-hospitalised control individuals (adjusted odds ratio, 7.96; 95% CI, 2.22-28.52; P = .001).
• IgG2 levels were lower in patients than in control individuals during both acute and convalescent phases; however, IgG, IgA, and IgM levels showed no differences between the two groups, except for slightly lower IgG levels during acute infection.
• B-cell concentrations measured during convalescence were lower in patients than in control individuals (P < .001), with 40% of patients vs 13% of control individuals having concentrations below the lower limit of the reference level (P < .001).
• Among 19 patients with persistent M protein at follow-up, seven were diagnosed with B-cell malignancies and 12 were diagnosed with MGUS.

IN PRACTICE

"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," the authors wrote.

SOURCE

The study was led by Tor Härnqvist, Department of Infectious Diseases, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. It was published online on July 24, 2026, in Scientific Reports.

LIMITATIONS

A very less proportion of eligible patients were enrolled in the study, and even lesser provided follow-up samples, potentially introducing selection bias. Control individuals were not recruited from a hospitalised population and had fewer underlying comorbidities than the patient group, which limited direct comparisons between the two groups.

DISCLOSURES

This study received financial support from grants provided by the Swedish state under the agreement between the Swedish government and county councils (ALF agreement), the Healthcare Board in Region Västra Götaland, and the Department of Research and Development at the NU Hospital Group. One author disclosed having a previous association with pharmaceutical organisations.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.