Pathophysiology
Entry into host
Rickettsia rickettsii can be transmitted to human hosts through the bite of an infected tick. As with other bacterium transmitted via ticks, the process generally requires a period of attachment of 4 to 6 hours. However, in some cases a Rickettsia rickettsii infection has been contracted by contact with tick tissues or fluids. Then, the bacteria induce their internalization into host cells via a receptor-mediated invasion mechanism.Researchers believe that this mechanism is similar to that of Rickettsia conorii. This species of Rickettsia uses an abundant cell surface protein called OmpB to attach to a host cell membrane protein called Ku70. It has previously been reported that Ku70 migrates to the host cell surface in the presence of "Rickettsia". Then, Ku70 is ubiquitinated by c-Cbl, an E3 ubiquitin ligase. This triggers a cascade of signal transduction events resulting in the recruitment of Arp2/3 complex. CDC42, protein tyrosine kinase, phosphoinositide 3-kinase, and Src-family kinases then activate Arp2/3. This causes the alteration of local host cytoskeletal actin at the entry site as part of a zipper mechanism. Then, the bacteria is phagocytosized by the host cell and enveloped by a phagosome.Studies have suggested that rOmpB is involved in this process of adhesion and invasion. Both rOmpA and rOmpB are members of a family of surface cell antigens (Sca) which are autotransporter proteins; they act as ligands for the Omp proteins and are found throughout the rickettsiae.
Chronic postoperative constipation is present in 7 to 8% of the operated cases. Postoperative enterocolitis, a severe manifestation, is present in the 10–20% of operated patients. Epidemiology
According to a 1984 study conducted in Maryland, Hirschsprungs disease appears in 18.6 per 100,000 live births. In Japan, it occurs at a similar rate of about one in 5,000 births (20 per 100,000). It is more common in male than female (4.32:1) and in white rather than nonwhite. Nine percent of the Hirschsprung cases were also diagnosed as having Down syndrome. Most cases are diagnosed before the patient is 10 years of age. History
The first report of Hirschsprungs disease dates to 1691, when it was described by Dutch anatomist Frederik Ruysch. However, the disease is named after Harald Hirschsprung, the Danish physician who first described two infants who died of this disorder in 1888.Hirschsprungs disease is a congenital disorder of the colon in which certain nerve cells, known as ganglion cells, are absent, causing chronic constipation. In patients with Hirschsprung disease, both myenteric and submucosal plexuses are absent. A barium enema is the mainstay of diagnosis of Hirschsprungs, though a rectal biopsy showing the lack of ganglion cells is the only certain method of diagnosis.The first publication on an important genetic discovery of the disease was from Martucciello Giuseppe et al. in 1992. The authors described a case of a patient with total colonic aganglionosis associated with a 46, XX, del 10 (q11.21 q21.2) karyotype.