This "acute schistosomiasis" is not, however, as important as the chronic forms of the disease. For S. mansoni and S. japonicum, these are "intestinal" and "hepatic schistosomiasis", associated with formation of granulomas around trapped eggs lodged in the intestinal wall or in the liver, respectively. The hepatic form of the disease is the most important, granulomas here giving rise to fibrosis of the liver and hepatosplenomegaly in severe cases. Symptoms and signs depend on the number and location of eggs trapped in the tissues. Initially, the inflammatory reaction is readily reversible. In the latter stages of the disease, the pathology is associated with collagen deposition and fibrosis, resulting in organ damage that may be only partially reversible.Granuloma formation is initiated by antigens secreted by the miracidium through microscopic pores within the rigid egg shell, and the immune response to granuloma, rather than the direct action of egg antigens, causes the symptoms. The granulomas formed around the eggs impair blood flow in the liver and, as a consequence, induce portal hypertension. With time, collateral circulation is formed and the eggs disseminate into the lungs, where they cause more granulomas, pulmonary arteritis and, later, cor pulmonale. A contributory factor to portal hypertension is Symmers fibrosis, which develops around branches of the portal veins.
People who have repeated mild head injuries over a prolonged period, such as boxers and Gridiron football players, are at risk for chronic traumatic encephalopathy (or the related variant dementia pugilistica), a severe, chronic disorder involving a decline in mental and physical abilities. Epidemiology
It is not known exactly how common PCS is. Estimates of the prevalence at three  months post-injury are between 24 and 84%, a variation possibly caused by different populations or study methodologies. The estimated incidence of PPCS (persistent postconcussive syndrome) is around 10% of mTBI cases. Since PCS by definition only exists in people who have had a head injury, demographics and risk factors are similar to those for head injury; for example, young adults are at higher risk than others for receiving head injury, and, consequently, of developing PCS.The existence of PCS in children is controversial. It is possible that childrens brains have enough plasticity that they are not affected by long-term consequences of concussion (though such consequences are known to result from moderate and severe head trauma). On the other hand, childrens brains may be more vulnerable to the injury, since they are still developing and have fewer skills that can compensate for deficits. Clinical research has found higher rates of post-concussion symptoms in children with TBI than in those with injuries to other parts of the body, and that the symptoms are more common in anxious children. Symptoms in children are similar to those in adults, but children exhibit fewer of them.