Carcinoid syndrome

Vignette says a 55 year old woman presents to the clinic with chief complaints of intermittent facial flushing, diarrhea and wheezing over the past 6 months; She also reports of having occasional episodes of crampy abdominal pain along with nausea, vomiting and loose stools occurring 3-4 times a day; She also complains of unintentional weight loss of 8 kg, in past 6 months; Examination shows holosystolic murmur at the left sternal border on auscultation; Vital signs show blood pressure of 120/80 mm of Hg, pulse rate of 102 bpm, respiratory rate of 18 breaths/min, oxygen saturation of 92% in RA and temperature of 99.9 F; 24-hour urinary excretion of 5-HIAA is increased; MRI of abdomen and pelvis shows small bowel mass with multiple liver metastasis; Diagnosis?

Diagnosis is carcinoid syndrome.

Carcinoid syndrome occurs when a carcinoid tumor (i.e. neuroendocrine tumors) commonly located in the GI tract (e.g. small bowel) metastasizes to the liver as serotonin produced by the tumor cannot be metabolized by the liver and leads to the distinctive clinical features.

Presents with abdominal pain, bronchospasm, flushing and diarrhea. Carcinoid syndrome is associated with right sided valvular lesions (i.e. tricuspid regurgitation, pulmonic stenosis); Triggers include alcohol, stress and spicy food; Triad of dermatitis, dementia, and diarrhea due to niacin deficiency (as tryptophan is shunted towards production of serotonin).

Location of carcinoid tumors:- Bronchus> Ileum > Rectum > Appendix > Colon.

Diagnosis:-

1. 24-hour urinary excretion of 5-HIAA is increased.

2. CT/MRI of abdomen and pelvis to localize the primary or metastatic carcinoid tumors.

3. Octreotide scintigraphy to localize the primary or metastatic carcinoid tumors.

4. Neuroendocrine markers (i.e. chromogranin, synaptophysin) are elevated.

5. Echocardiography shows valvular heart disorders (i.e. tricuspid regurgitation, pulmonic stenosis).

Management:-

1. Avoid triggers, correct electrolytes abnormalities (due to chronic diarrhea), niacin supplementation, loperamide for diarrhea, beta agonists for bronchospasm and antihistamines for flushing. 

2. Somatostatin analogues (e.g. octreotide) for symptom control.

3. Surgical resection for localized tumors.

4. Liver directed therapies (e.g. hepatic artery embolization, radiofrequency ablation, targeted radiotherapy (i.e. smart bombs)) for liver metastases.

HY point:- Chromogranin A and synaptophysin are the most specific immunohistochemical markers for the neuroendocrine tumors (e.g. small cell carcinoma of lung, carcinoid tumor, pheochromocytoma and neuroblastoma).