In the United States, they are most common in the second decade of life, with a rate of 0.3 cases per million in children under 3 years of age, and as high as 4.6 cases per million in adolescents aged 15–19 years. Nearly 80% of patients are aged less than 20 years of age. It is uncommon in patients younger than 5 years and older than 30 years.Internationally, the annual incidence rate averages less than 2 cases per million children. In the United Kingdom, an average of six children per year are diagnosed; mainly males in early stages of puberty. Due to the prevalence of diagnosis during teenage years, a link may exist between the onset of puberty and the early stages of this disease, although no research confirms this hypothesis.A grouping of three unrelated teenagers in Wake Forest, North Carolina, have been diagnosed with Ewing sarcoma. All three children were diagnosed in 2011 and all attended the same temporary classroom together while the school underwent renovation. A fourth teenager living nearby was diagnosed in 2009. The odds of this grouping are considered significant. Ewing sarcoma occurs about 10- to 20-fold more commonly in people of European descent compared to people of African descent.Ewing sarcoma is the second most common bone cancer in children and adolescents, with poor prognosis and outcome in ~70% of initial diagnoses and 10–15% of relapses. References
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Solitary rectal ulcer syndrome and colitis cystica profunda
Solitary rectal ulcer syndrome (SRUS, SRU), is a disorder of the rectum and anal canal, caused by straining and increased pressure during defecation. This increased pressure causes the anterior portion of the rectal lining to be forced into the anal canal (an internal rectal intussusception). The lining of the rectum is repeatedly damaged by this friction, resulting in ulceration. SRUS can therefore be considered to be a consequence of internal intussusception (a sub type of rectal prolapse), which can be demonstrated in 94% of cases. It may be asymptomatic, but it can cause rectal pain, rectal bleeding, rectal malodor, incomplete evacuation and obstructed defecation (rectal outlet obstruction). Symptoms
Symptoms include:
Straining during defecation
Mucous rectal discharge
Rectal bleeding
Sensation of incomplete evacuation (tenesmus)
constipation, or more rarely diarrhea
fecal incontinence (rarely)

Prevalence
The condition is thought to be uncommon. It usually occurs in young adults, but children can be affected too. Cause
The essential cause of SRUS is thought to be related to too much straining during defecation. Overactivity of the anal sphincter during defecation causes the patient to require more effort to expel stool. This pressure is produced by the modified valsalva manovoure (attempted forced exhalation against a closed glottis, resulting in increased abdominal and intra-rectal pressure). Patiest with SRUS were shown to have higher intra-rectal pressures when straining than healthy controls. SRUS is also associated with prolonged and incomplete evacuation of stool.More effort is required because of concomitant anismus, or non-relaxation/paradoxical contraction of puborectalis (which should normally relax during defecation).