Two patients are presented with intestinal pseudo-obstruction and malformations of their intestinal muscularis propria. Histopathological findings in each case indicate a distinct alteration of intestinal muscle architecture. The 1st patient, a teenager with lifelong constipation, had an additional circular muscle tunic in 2 dilated segments of his large intestine. The 2nd patient, an infant with multiple malformations, had diffuse abnormal layering of his small intestine. The rare reports of other individuals with similar pathological findings are discussed.