Constipation, abdominal distension and megecolon are well known clinical findings with hypothyroidism. As these findings may strongly resemble that ot Hirschsprung's disease, ileus due to hypothyroidism is called to be "pseudo-Hirschsprung's disease". A 53 days old baby girl was admitted to Kyushu University Hospital with abdominal distension and vomitting. A plain abdominal X-ray film showed a dilation of the intestinal loops. However, a barium enema showed the normal sized colon. The recto-anal reflex was absent in manometry. Histochemical staining of acetylcholinesterase activity showed no increased nerve fibers. Blood culture revealed Proteus morganii. Thyroid function test showed hypothyroidism pattern: low T3 and T4 and high TSH. Chromosomal analysis showed 21 trisomy. No surgical intervention was required. The clinical symptoms disappeared by conservative therapy. In recovery stage, recto-anal reflex in manometry was present. Thyroid function test showed normal pattern. This case was considered to be sepsis and transient hypothyroidism with Down's syndrome. So ileus due to hypothyroidism and the association with Down's syndrome and respiratory distress syndrome were briefly discussed.
