Intermittent attacks of diarrhea, flushing, and cyanosis describe which syndrome?

• A. Carcinoid syndrome
• B. Horner's syndrome
• C. SVC syndrome
• D. Central tumors

Answer: (A)

This presentation is classic for carcinoid syndrome, caused by a neuroendocrine tumor that releases serotonin and other vasoactive substances into the circulation. The episodic flushing with accompanying diarrhea arises from serotonin-driven increases in gut motility and vasodilation. Cyanosis can occur during these episodes as the vasomotor changes and hypoxemia intensify. A key point is that these substances reach the systemic circulation when liver metastases are present or when substances bypass hepatic metabolism, allowing widespread effects. Over time, continued secretion can also lead to right-sided valvular heart disease from fibrosis.

Other options don’t fit this pattern. Horner’s syndrome features ptosis, miosis, and anhidrosis, not diarrhea or flushing. SVC syndrome presents with facial and upper-body edema and dilated chest veins due to venous obstruction, not the secretory diarrhea and flushing. Central tumors is too broad and lacks the characteristic hormonal symptom cluster. Diagnosis is supported by elevated urinary 5-HIAA and imaging with somatostatin receptor–positive scans; management includes somatostatin analog therapy and tumor-directed treatments.