Megacystis Microcolon Intestinal Hypoperistalsis Syndrome(MMIH)
01 January 2001
Megacystis microcolon intestinal hypoperistalsis (MMIH) is a rare, usually sporadic and lethal condition with a strong female predominance (4:1). Familial cases have been reported. It is characterised by a large distended but unobstructed bladder, a short, dilated, malfixed small bowel with no obstruction and distal microcolon with absent or ineffective peristalsis. It is thought that decreased gastric and intestinal mobility results in polyhydramnios. Hydronephrosis and hydroureter are present in most cases.
Histologically, unlike Hirschsprung's disease, there are normal or increased ganglia and if the infant survives all of the segments of the colon become normal in size or dilated. Poor gastrointestinal function leads to malnutrition and infants have died despite hyperalimentation with sepsis seen as a final complication in many.
A less severe familial visceral myopathy, chronic idiopathic intestinal pseudo obstruction (CIIP) is seen in adolescents or young adults and characterised by bladder, ureteral, intestinal and oesophageal dysfunction. Electromicroscopic studies show similar vacuolar degeneration of smooth muscle in MMIH and CIIP.An enlarged bladder, dilated small bowel and polyhydramnios are the cardinal features of MMIH. Hydronephrosis and hydroureter are almost always present. Although polyhydramnios may not be seen until later in pregnancy a normal fluid volume suggests lack of complete urethral obstruction. The incidence of other anomalies is about 15%. In the absence of a family history, a definitive diagnosis especially in the second trimester may be very difficult. Associated anomalies may include omphalocele, cardiac anomalies, and cleft palate.
In one case, multiple cardiac rhabdomyomas were identified in a patient with MMHIS. It has been speculated that the gene for tuberous sclerosis (associated with rhabdomyoma) and MMIHS may be located close to one another or chromosome 9.
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