What is Serositis
Serositis is inflammation of the serous membranes (pleura, pericardium, or peritoneum) that line body cavities, typically manifesting with effusion and characterized by the presence of inflammatory cells in the serous fluid.
Anatomical Definition and Pathology
Serositis represents inflammation affecting one or more serous membranes, including the pleura (pleuritis), pericardium (pericarditis), and peritoneum (peritonitis), with associated fluid accumulation in these cavities 1.
The inflammatory process involves infiltration of the serous membrane with lymphocytes, plasma cells, and neutrophils, similar to other inflammatory conditions 1.
When multiple serous membranes are simultaneously involved, the condition is termed polyserositis, which requires inflammation of two or more serous membranes confirmed by imaging, with at least one serous fluid demonstrating exudative characteristics 2.
Clinical Manifestations
Serositis presents with cavity-specific symptoms: pleuritis causes chest pain and dyspnea, pericarditis causes chest pain and potential cardiac tamponade, and peritonitis causes abdominal pain and ascites 1.
The condition may be accompanied by systemic manifestations including fever, tachycardia, and constitutional symptoms, particularly when associated with underlying systemic disease 1.
In severe cases, serositis can be life-threatening, with complications including cardiac tamponade, respiratory failure, and diffuse intravascular coagulation 1.
Diagnostic Context in Specific Diseases
Inflammatory Bowel Disease
In Crohn's disease, serositis is a characteristic transmural feature that helps distinguish it from ulcerative colitis, where serositis is typically absent except in fulminant colitis 1.
This distinction is diagnostically important: serositis presence suggests Crohn's disease over ulcerative colitis in the differential diagnosis of inflammatory bowel disease 1.
Systemic Lupus Erythematosus
Serositis occurs in approximately 12-13% of SLE patients and represents one of the American College of Rheumatology classification criteria for the disease 3, 4.
At the time of serositis presentation in SLE, 92% of patients have active disease in other organ systems, indicating it typically occurs as part of multisystem involvement rather than in isolation 3.
Adult-Onset Still's Disease
- Serositis (including pericarditis, pleuritis, and peritonitis) is a recognized systemic manifestation of AOSD, particularly in the monocyclic pattern characterized by predominant systemic symptoms 1.
Uremia
- Serositis, particularly pericarditis and pleuritis, represents a classic sign of advanced uremia in patients with kidney failure 1.
Etiological Categories
The most common causes of serositis include neoplastic disease (approximately one-third of cases), infectious diseases, and autoimmune conditions 2.
Idiopathic recurrent serositis (IRS) accounts for a substantial proportion of cases, with approximately 70% of recurrent pericarditis cases being idiopathic and related to innate immunity abnormalities 5.
In more than one-third of polyserositis cases, the etiology remains unknown despite thorough investigation 2.
Other causes include chronic graft-versus-host disease following allogeneic hematopoietic cell transplant, which is a rare but recognized manifestation 6.
Diagnostic Approach
Pleura and pericardium are the most commonly involved sites (83% of polyserositis cases), followed by peritoneal involvement 2.
Antinuclear antibody positivity in serum and elevated adenosine deaminase levels in pleural effusion are significantly associated with autoimmune etiologies 2.
Elevated pleural lactate dehydrogenase levels are significantly associated with neoplastic causes 2.
Serous fluid analysis should demonstrate exudative characteristics to confirm true serositis rather than transudative effusions from other causes 2.
Clinical Pitfalls
Do not assume serositis always indicates a specific underlying disease—it can be idiopathic, and extensive workup may not reveal a cause in over one-third of cases 2.
In patients with previous cancer, serositis may represent disease recurrence: in 9 of 14 patients with prior malignancy, polyserositis represented cancer recurrence 2.
Ascites in the context of serositis should not be automatically attributed to nephrotic syndrome, heart failure, or portal hypertension—it can be a direct manifestation of peritoneal serositis, particularly in autoimmune conditions 4.
Serositis occurring during immunosuppressant taper (as seen in 12 of 20 chronic GVHD cases) suggests the condition may be precipitated by reduced immunosuppression 6.