D3.478 - Microsplenia: Spleen Size Reduction as a Comprehensive Biomarker for Immune-Related Diseases, Disease Monitoring, and Treatment Response

The spleen is a central but underutilized immune organ in clinical practice. Microsplenia, defined as a pathological reduction in spleen size, has received limited attention despite its potential relevance in immune dysregulation, chronic inflammation, malignancy, and treatment monitoring.

Objectives: To evaluate microsplenia as a comprehensive imaging biomarker for immune-related diseases, disease progression, and treatment response using ultrasound-based spleen size dynamics.

We performed a retrospective analysis spanning nearly ten years, including ultrasound spleen measurements obtained in internal medicine departments. Microsplenia was defined as spleen length × width < 90 × 30 mm. Data were analyzed across multiple disease categories. Findings were complemented by targeted case reports and a focused literature review.

Among the analyzed cohort, microsplenia was identified in 169 patients across 55 distinct diseases, encompassing infectious, allergic, autoimmune, oncological, and advanced systemic conditions. Pronounced spleen size reduction was observed in patients with chronic immune-mediated diseases, including asthma, allergies, and autoimmune disorders, as well as during and after targeted therapies.In a representative case of ALK-negative anaplastic large cell lymphoma, serial ultrasound demonstrated rapid spleen size reduction with associated splenic infarctions during targeted treatment, correlating with favorable therapeutic response. In another case, a patient with advanced liver cirrhosis showed a transition from splenomegaly to microsplenia in terminal stages, reflecting immune and vascular collapse.

Microsplenia represents a dynamic, non-invasive biomarker reflecting immune system activity, disease progression, and treatment response across diverse immune-related conditions. Ultrasound-based spleen monitoring may offer a valuable tool for personalized disease stratification and therapy assessment. Prospective studies are warranted to standardize thresholds, elucidate underlying mechanisms, and integrate microsplenia into routine immunological and clinical practice.