Hypogammaglobulinemia in patients affected by limited cutaneous systemic sclerosis: Case series and review of the literature

Background: Hypogammaglobulinemia is a condition that can be related to both primary and secondary immunodeficiencies. While the role of primary immunodeficiency in immune-mediated diseases is well known, its occurrence in systemic sclerosis is not reported. Objectives: This study aims to describe the clinical features associated with hypogammaglobulinemia in a cohort of limited cutaneous systemic sclerosis patients. Methods: We retrospectively reviewed medical records of systemic sclerosis patients from two Italian referral centres (2010–2024). Included patients had limited cutaneous systemic sclerosis and presented reduced serum concentrations of one or more Ig isotypes (IgG < 700 mg/dL, IgA < 70 mg/dL or IgM < 50 mg/dL) in at least two separate measurements. Patients with secondary causes of hypogammaglobulinemia were excluded. Data collected included demographics, clinical features, Ig levels, infection history and comorbidities. Results: We identified 30 systemic sclerosis patients (93% female, mean age 62 years) with limited cutaneous involvement and hypogammaglobulinemia. Most patients were positive for anti-centromere antibodies and received periodic intravenous infusions of prostaglandin analogues. No patient received immunosuppressive therapy. Median (interquartile range) serum IgG levels 519.5 (175) mg/dL, median IgA 65.5 (48) mg/dL and median IgM 71.5 (49) mg/dL. Four patients who met the European Society for Immunodeficiencies (ESID) criteria for common variable immunodeficiency experienced recurrent infections and had associated immune-mediated diseases. Five patients had selective IgA deficiency, with frequent immune-mediated comorbidities (thyroiditis, Sjögren’s syndrome, arthritis, psoriasis). The other patients exhibited mild IgG deficiency without a significant infectious history. Conclusions: This is the first study describing a cohort of patients with limited cutaneous systemic sclerosis and hypogammaglobulinemia. Our population presented a high prevalence of immune-mediated comorbidities but low infection rates. Further research is needed to explore the underlying mechanisms and clinical significance of hypogammaglobulinemia in these patients.