Serositis is seen in numerous conditions:

- Lupus erythematosus (SLE), for which it is one of the criteria,

- Rheumatoid arthritis

- Familial Mediterranean fever (FMF)

- Chronic renal failure

- Juvenile idiopathic arthritis

- Inflammatory bowel disease (especially Crohn's disease)

- Acute appendicitis

- Diffuse cutaneous systemic sclerosis

Serositis refers to inflammation of the serous tissues of the body, the tissues lining the lungs (pleura), heart (pericardium), and the inner lining of the abdomen (peritoneum) and organs within. It is commonly found with fat wrapping or creeping fat.

25% of cases progress to severe destructive arthritis. In the United States and Canada, mortality is estimated at about 4% and in Europe, mortality is estimated at 21.7%.

The cause of JIA remains a mystery. However, the disorder is autoimmune — meaning that the body's own immune system starts to attack and destroy cells and tissues (particularly in the joints) for no apparent reason. The immune system is thought to be provoked by changes in the environment, in combination with mutations in many associated genes and/or other causes of differential expression of genes. Experimental studies have shown that certain mutated viruses may be able to trigger JIA. The disease appears to be more common in girls, and the disease is most common in Caucasians.

Associated factors that may worsen or have been linked to rheumatoid arthritis include:

- Genetic predisposition; When one family member has been diagnosed with rheumatoid arthritis or another autoimmune disorder, the chances are higher that other family members or siblings may also develop arthritis.

- Females are more likely to develop rheumatoid arthritis than males at all ages.

- A strong belief is held that psychological stress may worsen the symptoms of rheumatoid arthritis. However, when the emotional stress is under control, the arthritis symptoms do not always disappear, suggesting that the association is not straightforward.

- Though no distinct immune factor has been isolated as a cause of arthritis, some experts believe that the triggering factor may be something like a virus which then disappears from the body after permanent damage is done.

- Because rheumatoid arthritis is more common in women, perhaps sex hormones may play a role in causing or modulating arthritis. Unfortunately, neither sex hormone deficiency nor replacement has been shown to improve or worsen arthritis.

The cause of JIA, as the word "idiopathic" suggests, is unknown and an area of active research. Current understanding of JIA suggests that it arises in a genetically susceptible individual due to environmental factors.

JIA occurs in both sexes, but like other rheumatological diseases, is more common in females. Symptoms onset is frequently dependent on the subtype of JIA and is from the preschool years to the early teenaged years.

Periodic fever syndromes (also known as autoinflammatory diseases or autoinflammatory syndromes) are a set of disorders characterized by recurrent episodes of systemic and organ-specific inflammation. Unlike autoimmune disorders such as systemic lupus erythematosus, in which the disease is caused by abnormalities of the adaptive immune system, patients with autoinflammatory diseases do not produce autoantibodies or antigen-specific T or B cells. Instead, the autoinflammatory diseases are characterized by errors in the innate immune system.

The syndromes are diverse, but tend to cause episodes of fever, joint pains, skin rashes, abdominal pains and may lead to chronic complications such as amyloidosis.

Most autoinflammatory diseases are genetic and present during childhood. The most common genetic autoinflammatory syndrome is familial Mediterranean fever, which causes short episodes of fever, abdominal pain, serositis, lasting less than 72 hours. It is caused by mutations in the MEFV gene, which codes for the protein pyrin.

Pyrin is a protein normally present in the inflammasome. The mutated pyrin protein is thought to cause inappropriate activation of the inflammasome, leading to release of the pro-inflammatory cytokine IL-1β. Most other autoinflammatory diseases also cause disease by inappropriate release of IL-1β. Thus, IL-1β has become a common therapeutic target, and medications such as anakinra, rilonacept, and canakinumab have revolutionized the treatment of autoinflammatory diseases.

However, there are some autoinflammatory diseases that are not known to have a clear genetic cause. This includes PFAPA, which is the most common autoinflammatory disease seen in children, characterized by episodes of fever, aphthous stomatitis, pharyngitis, and cervical adenitis. Other autoinflammatory diseases that do not have clear genetic causes include adult-onset Still's disease, systemic-onset juvenile idiopathic arthritis, Schnitzler syndrome, and chronic recurrent multifocal osteomyelitis. It is likely that these diseases are multifactorial, with genes that make people susceptible to these diseases, but they require an additional environmental factor to trigger the disease.

Another example that shows that autoinflamatory conditions may not be genetic in origin is found in a report published in "Nature" which shows that diet is very important in the development of such diseases. The ingestion levels of highly saturated fats and cholesterol, (high fat diet, HFD) affects the microbiota composition of the gut. Changes in the microbiota induced by a HFD are protective against the susceptibility to develop osteomyelitis (autoimmune disease) as compared with the changes induced by a low-fat diet. The changes in the microbiome of individuals under HFD showed a reduction in "Prevotella" abundance and were accompanied by significantly reduced expression levels of pro-Interleukin-1β in distant neutrophils.

Treatment with either glucocorticoids, methotrexate, anakinra, or tocilizumab has been examined. Anakinra has been shown to resolve the clinical features of the disease in 87% of patients. It also induces remission in half of corticosteroid-resistant patients. The results of another study were similar, with half of the patients responding to treatment with Anakinra. Canakinumab, an antibody to

interleukin-1 beta, is indicated for treatment in patients who respond poorly to other treatments.

SLE causes an increased rate of fetal death "in utero" and spontaneous abortion (miscarriage). The overall live-birth rate in SLE patient has been estimated to be 72%. Pregnancy outcome appears to be worse in SLE patients whose disease flares up during pregnancy.

Miscarriages in the first trimester appear either to have no known cause or to be associated with signs of active SLE. Later losses appear to occur primarily due to the antiphospholipid syndrome, in spite of treatment with heparin and aspirin. All women with lupus, even those without previous history of miscarriage, are recommended to be screened for antiphospholipid antibodies, both the lupus anticoagulant (the RVVT and sensitive PTT are the best screening battery) and anticardiolipin antibodies.

The processes that lead to drug-induced lupus erythematosus are not entirely understood. The exact processes that occur are not known even after 50 years since its discovery, but many studies present theories on the mechanisms of DIL.

A predisposing factor to developing DIL is N-acetylation speed, or the rate at which the body can metabolize the drug. This is greatly decreased in patients with a genetic deficiency of the enzyme N-acetyltransferase. A study showed that 29 of 30 patients with DIL were slow acetylators. In addition, these patients had more hydralazine metabolites in their urine than fast acetylators. These metabolites (byproducts of the interactions between the drug and constituents in the body) of hydralazine are said to have been created when white blood cells have been activated, meaning they are stimulated to produce a respiratory burst. Respiratory burst in white blood cells induces an increased production of free radicals and oxidants such as hydrogen peroxide. These oxidants have been found to react with hydralazine to produce a reactive species that is able to bond to protein. Monocytes, one type of white blood cell, detect the antigen and relay the recognition to T helper cells, creating antinuclear antibodies leading to an immune response. Further studies on the interactions between oxidants and hydralazine are necessary to understand the processes involved in DIL.

Of the drugs that cause DIL, hydralazine has been found to cause a higher incidence. Hydralazine is a medication used to treat high blood pressure. Approximately 5% of the patients who have taken hydralazine over long periods of time and in high doses have shown DIL-like symptoms. Many of the other drugs have a low to very low risk to develop DIL. The following table shows the risk of development of DIL of some of these drugs on a very to high scale.

- High risk:

- Procainamide (antiarrhythmic)

- Hydralazine (antihypertensive)

Neonatal lupus is the occurrence of SLE symptoms in an infant born from a mother with SLE, most commonly presenting with a rash resembling discoid lupus erythematosus, and sometimes with systemic abnormalities such as heart block or hepatosplenomegaly. Neonatal lupus is usually benign and self-limited. Still, identification of mothers at highest risk for complications allows for prompt treatment before or after birth. In addition, SLE can flare up during pregnancy, and proper treatment can maintain the health of the mother for longer.

Drug-induced lupus erythematosus (DIL or DILE) is an autoimmune disorder (similar to systemic lupus erythematosus [SLE]) caused by chronic use of certain drugs. These drugs cause an autoimmune response (the body attacks its own cells) producing symptoms similar to those of SLE. There are 38 known medications to cause DIL but there are three that report the highest number of cases: hydralazine, procainamide, and isoniazid. While the criteria for diagnosing DIL has not been thoroughly established, symptoms of DIL typically present as muscle pain and joint pain. Generally, the symptoms recede after discontinuing use of the drugs.

SLE, like many autoimmune diseases, affects females more frequently than males, at a rate of about 9 to 1. The X chromosome carries immunological related genes, which can mutate and contribute to the onset of SLE. The Y chromosome has no identified mutations associated with autoimmune disease.

Hormonal mechanisms could explain the increased incidence of SLE in females. The onset of SLE could be attributed to the elevated hydroxylation of estrogen and the abnormally decreased levels of androgens in females. In addition, differences in GnRH signalling have also shown to contribute to the onset of SLE. While females are more likely to relapse than males, the intensity of these relapses is the same for both sexes.

In addition to hormonal mechanisms, specific genetic influences found on the X chromosome may also contribute to the development of SLE. Studies indicate that the X chromosome can determine the levels of sex hormones. A study has shown an association between Klinefelter syndrome and SLE. XXY males with SLE have an abnormal X–Y translocation resulting in the partial triplication of the PAR1 gene region.

SLE is presumably caused by a genetic susceptibility coupled with an environmental trigger which results in defects in the immune system. One of the factors associated with SLE is vitamin D deficiency.

Causes of high serum-ascites albumin gradient (SAAG or transudate) are:

- Cirrhosis – 81% (alcoholic in 65%, viral in 10%, cryptogenic in 6%)

- Heart failure – 3%

- Hepatic venous occlusion: Budd–Chiari syndrome or veno-occlusive disease

- Constrictive pericarditis

- Kwashiorkor (childhood protein-energy malnutrition)

Causes of low SAAG ("exudate") are:

- Cancer (metastasis and primary peritoneal carcinomatosis) – 10%

- Infection: Tuberculosis – 2% or spontaneous bacterial peritonitis

- Pancreatitis – 1%

- Serositis

- Nephrotic syndrome

- Hereditary angioedema

Other rare causes:

- Meigs syndrome

- Vasculitis

- Hypothyroidism

- Renal dialysis

- Peritoneum mesothelioma

- Abdominal tuberculosis

Estimates of the rate of HCV vertical transmission range from 2–8%; a 2014 systematic review and meta-analysis found the risk to be 5.8% in HCV-positive, HIV-negative women. The same study found the risk of vertical transmission to be 10.8% in HCV-positive, HIV-positive women. Other studies have found the risk of vertical transmission to be as high as 44% among HIV-positive women. The risk of vertical transmission is higher when the virus is detectable in the mother's blood.

Evidence does not indicate that mode of delivery (i.e. vaginal vs. cesarean) has an effect on vertical transmission.

For women who are HCV-positive and HIV-negative, breastfeeding is safe; however, CDC guidelines suggest avoiding breastfeeding if a woman's nipples are "cracked or bleeding" to reduce the risk of transmission.

Ascites is the abnormal buildup of fluid in the abdomen. Technically it is more than 25 mL of fluid in the peritoneal cavity. Symptoms may include increased abdominal size, increased weight, abdominal discomfort, and shortness of breath. Complications can include spontaneous bacterial peritonitis.

In the developed world the most common cause is liver cirrhosis. Other causes include cancer, heart failure, tuberculosis, pancreatitis, and blockage of the hepatic vein. In cirrhosis the underlying mechanism involves high blood pressure in the portal system and dysfunction of blood vessels. Diagnosis is typically based on a examination together with ultrasound or a CT scan. Testing the fluid can help in determining the underlying cause.

Treatment often involves a low salt diet, medication such as diuretics, and draining the fluid. A transjugular intrahepatic portosystemic shunt (TIPS) may be placed but is associated with complications. Effects to treat the underlying cause, such as by a liver transplant may be considered. Of those with cirrhosis, more than half develop ascites in the ten years following diagnosis. Once ascites has developed in this group, average life expectancy is less than three years. The term is from the Greek "askítes" meaning "baglike".

Pregnant women who contract HEV are at significant risk of developing fulminant hepatitis with maternal mortality rates as high as 20–30%, most commonly in the third trimester . A 2016 systematic review and meta-analysis of 47 studies that included 3968 people found maternal case-fatality rates (CFR) of 20.8% and fetal CFR of 34.2%; among women who developed fulminant hepatic failure, CFR was 61.2%.