A 48 year old man presents with episodic watery diarrhea for five months, which was predominantly nocturnal. He had also lost 8 kg of weight during the preceding year. His medical history is unremarkable, and he is not on any drugs. There is no significant history of travel. His serum albumin is found to be 2.5 g/dL (normal: 3.5 to 5.5 g/dL).
Na+: 132 mEq/L (135 - 145) K+: 3.4 mEq/L (3.5 - 5.5) Cl-: 97 mEq/L (95 - 105)
No amoeba, ova or cysts identified No pus cells or erythrocytes Fecal fat analysis: 9 g/24h (normal: 2 - 6) Bacterial and protozoal cultures: negative
22 mcg/dl (<3: adrenal insufficiency; 3-19: indeterminate; 19-25: unambiguously normal)
The duodenal mucosa shows pale yellow shaggy areas alternating with erythematous regions. Biopsies reveal expanded villi containing macrophages which stain positive to the Periodic Acid-Schiff (PAS) stain.