Mucosa
FIGURE 1
Submucosa our patient presented with diffuse peritonitis and was ultimately found to have a perforation of her descending colon requiring a left colectomy . Final pathology was notable for a focal absence of the muscularis propria at the site of perforation . Our patient ’ s original episode of spontaneous bowel perforation associated with segmental absence of intestinal musculature ( SAIM ) was originally described by Nawar and Sawyer . 1
Muscularis propria
Figure 1 : Demonstration of abrupt absence of muscularis propria .
DISCUSSION
In the literature , just over 30 cases of SAIM have been described . 2 The vast majority of cases have presented in the neonatal period and have often been associated with prematurity and low birth weight . 3 Though this association is established , the pathogenesis of muscularis propria absence is poorly understood .
Submucosa
FIGURE 2
Circular muscle layer
Given the early presentation of SAIM in most patients , many have theorized the pathophysiology is due to an abnormality in embryogenesis . Theories regarding the specific embryologic dysfunction include a failure of intestinal diverticulae to regress and over-resorption of muscles during regression of the omphalomesenteric duct . 1 While most support an embryologic etiology , some favor the idea of an acquired cause of SAIM such as hypertensive vascular disease or mesenteric vessel thrombosis leading to bowel ischemia . 1
Figure 2 : Demonstration of attenuation of the longitudinal muscle layer followed by abrupt absence of both muscle layers .
There was no evidence of malignancy noted within the bowel or the associated lymph nodes . The microscopic examination also identified gradual attenuation of the external longitudinal muscle layer leading to an area of complete absence of both muscle layers associated with the area of transmural perforation . The remainder of the specimen was examined for a similar defect of the muscularis propria , and no additional defect was identified . Figures 1
Longitudinal muscle layer
and 2 demonstrate pathologic samples of the colon adjacent to the site of perforation . Figure 1 demonstrates an abrupt absence of the muscularis propria . Figure 2 shows attenuation of the external longitudinal muscle layer of the muscularis propria followed by an abrupt absence of both layers . Final pathologic analysis of the completion colectomy specimen revealed no additional areas with absent muscularis propria . Of significance , five years prior to this episode ,
Our patient first presented at 64 years old , making a congenital abnormality less likely . This patient also presented with two episodes of spontaneous bowel perforation without hyper- or hypotension and without evidence of bowel ischemia . Additionally , the patient ’ s daughter suffered an episode of spontaneous bowel perforation of unknown etiology . The fact that both mother and daughter suffered spontaneous bowel perforation suggests there may be a genetic component to the underlying cause of SAIM . Furthermore , the patient and her daughter both had OI . OI has not been previously implicated in SAIM or spontaneous bowel perforation . However , first-degree relatives each suffering from these two rare conditions suggests that OI and spontaneous bowel perforation in adulthood may be associated with one another . If such an association does exist , the pathophysiologic basis is
West Virginia Medical Journal • June 2024 • 21