RAMB - Dezembro

lara

APHS

896

ssoc

ras

2016; 62(9):895-900

eases, past or current diagnosis of malignancy and histo-

ry of solid organ transplants.

Recent studies in the US have shown an MC incidence

rate of 7.1 per 100,000 individuals/year for CC, and 12.6

per 100,000 individuals/year for LC.

The global prevalence

of MC was observed at 103.0 per 100,000 individuals, with

39.3 per 100,000 individuals for CC and 63.7 per 100,000

individuals for LC. These figures are similar to the data ob-

tained for classic inflammatory bowel diseases (IBD).

MC is typically a disease of the elderly, with an aver-

age age at diagnosis of 65 years.

CC is around 20 times

more frequent in women, while LC is equally distributed

between men and women.

MC is a rare phenomenon in

children and 25% of patients with MC are aged less than

45 years, which reflects the need for investigation in young

patients with chronic diarrhea.

athogenesis

The pathophysiology of MC is still unknown, but it is be-

lieved that it is due to a multifactorial etiology, involving

an exacerbated immune response to harmful luminal

agents in the mucosa of these individuals.

1,3,4

There is strong evidence of an autoimmune basis for

CC and LC, both of which are associated with diseases

such as celiac disease (12%), thyroid diseases (10.3%),

Sjögren’s syndrome (3.4%) and

diabetes mellitus

(1.7%).

3-5

Various autoantibodies and phenotypes can be found

along with MC, including the DR3 phenotype of human

leukocyte antigen (HLA). However, no specific autoanti-

body has been identified as relevant in the diagnosis.

3,4

Several luminal factors have an important role in the

pathogenesis of MC. Many drugs are cited, such as aspirin,

nonsteroidal anti-inflammatory drugs (NSAIDs), proton

pump inhibitors (PPIs), sertraline, ranitidine, simvastatin,

carbamazepine, and more. These medications should be

stopped when MC is diagnosed, which may result in im-

provement of the symptoms reported by the patient.

3,4

Malabsorption of bile acids was found in up to 60%

of patients with LC and 44% of patients with CC, sup-

porting the idea that this may be the cause of MC.

3,4

In-

creases were also reported in interferon gamma (IFN-

tumor necrosis factor alpha (TNF-

), interleukin 1 beta

(IL-1

), and a profile of Th1 cytokines, which are sug-

gested to be involved in the inflammatory process.

3,4

As for environmental factors, the major etiologic role

is played by cigarettes. Smoking is more prevalent among

patients with MC, and studies indicate an association

with lung cancer. It has also been demonstrated that MC

involvement in individuals that smoke occurs around 10

years earlier, increasing the relevance of this habit.

3-5

linical

presentation

LC and CC are not distinguishable from each other based

on symptoms and clinical presentation. Differentiation

between the two is undertaken through histology only.

1,3,4,6

The main symptomnoted is chronic, typically aqueous,

non-bloody diarrhea; nocturnal diarrhea is common (50%),

as well as urgency (70%) and fecal incontinence (40%).

1,3-10

Abdominal pain is a common symptom and may be

present in up to 50% of patients. A differential diagnosis

with irritable bowel syndrome (IBS) should therefore be

investigated.

1,3,5,6

Weight loss is also observed during ac-

tive disease in almost half of patients. Celiac disease should

be investigated and discarded in patients with marked

weight loss, steatorrhea, iron deficiency anemia, and those

who do not respond to the usual therapy.

1,5

The presence of fever, vomiting, or hematochezia should

indicate the possibility of an alternative diagnosis.

aboratory

and

imaging

diagnosis

The diagnosis of MC depends on a proper medical histo-

ry, with the exclusion of other diseases, normal radiolog-

ical/endoscopic findings and endoscopic biopsies with

histopathological findings consistent with MC.

Medical history helps to rule out other etiologies that

can cause a similar clinical presentation, such as IBD, ce-

liac disease and IBS. Laboratory and radiographic exam-

inations also rule out other pathologies, but are typical-

ly normal.

Only non-specific changes may be found, such

as moderately high C-reactive protein and anemia. A stool

examination usually reveals the absence of pathological

microorganisms. The diagnostic accuracy of calprotectin

and fecal lactoferrin is low.

Barium enema and colonoscopy are usually normal,

although subtle changes may be observed in the mucosa,

such as edema, enanthem and abnormal vascular pattern,

occasionally seen during colonoscopy.

istological

diagnosis

The diagnosis of MC is based solely on results of typical

microscopic changes in mucosal biopsies of the colon. In

CC (Figure 1) we can observe thickening of the subepi-

thelial collagen layer together with chronic mononucle-

ar inflammation in the lamina propria and damaged ep-

ithelial cells with an occasional increase in the number

of intraepithelial lymphocytes. The enlargement of the

subepithelial collagen layer is greater than 10 μm, in con-

trast with the normal basal membrane which measures

less than 3 μm.

The thickening of the collagen layer can vary and is

most prominent in the ascending and transverse colon; it