Idiopathic Hypertrophic Pyloric Stenosis in an Adult, a Potential Mimic of Gastric Carcinoma

Primary or idiopathic hypertrophy of the pyloric muscle (IHPM) is a rare entity with uncertain pathogenesis which both clinically and pathologically mimics gastric cancer. We present a rare late-occurring case of IHPM in a 71-year-old Caucasian man with no apparent predisposing factor. Imaging studies demonstrated gastric distension with air fluid levels and no evidence of extrinsic compression. At upper endoscopy, massive gastric distension and no evidence of any ulcer or other mucosal defects were observed. Microscopically, marked hypertrophy of muscularis mucosa with smooth muscle cells arranged in whorls and fascicles was present which gradually transitioned to normal areas. The muscle fibers stained with smooth muscle actin and trichrome stain highlighted fibrosis between the muscle fibers. Although uncommon, IHPM can clinically and histologically mimic other proliferations in the gastric wall, such as gastrointestinal stromal tumor or a spindle cell neoplasm. The recent advances in understanding the pathogenesis of IHPM are discussed. 1. Introduction Primary or idiopathic hypertrophy of the pyloric muscle (IHPM) in adults is a relatively rare, yet well-established entity [1, 2]. The incidence of congenital hypertrophic pyloric stenosis is reported between 0.25% and 0.5% of all live births in literature [3, 4]. The adult variant, however, is even more uncommon with less than 200 cases reported in the English literature [5]. Although, it is unclear what causes this condition, theories have been proposed such as the persistence of a mild manifestation of a juvenile form into adulthood [2, 6]. IHPM appears to be far more common in middle aged males [7, 8]. We report a case in an older male with no prior history of gastrointestinal symptoms and no apparent precipitating factor. 2. Report of a Case A 71-year-old Caucasian man had been experiencing abdominal distension, nausea, and vomiting for three months. His symptoms worsened progressively over the previous two weeks when he was referred to our institution for further evaluation. The abdominal distention and vomiting appeared to be mostly postprandial, and the vomitus consisted of mainly undigested food and no bile. His symptoms were independent of the type and consistency of the type of the food ingested. His past medical history was significant for cardiovascular diseases, end stage renal disease, and diabetes mellitus with no history of gastrointestinal problems. Abdominal films obtained before admission showed massive gastric distension. Physical exam revealed a soft, mildly distended abdomen. No