Carcinoid Syndrome
Carcinoid syndrome is a serious, chronic cluster of endocrine symptoms produced by neuroendocrine tumors (NETs) that arise from enterochromaffin cells, mostly in the appendix, small intestine, stomach or lungs. It is driven by surges of chemical mediators released into the circulation, including serotonin (5-HT), bradykinin, histamine, tachykinins and prostaglandins. When these substances come from a gut tumor, the liver normally breaks them down and inactivates them. Once the tumor has spread to the liver, or when it originates in the lung, they pass straight into the general circulation and trigger symptoms.
The earliest and most striking skin sign is episodic facial flushing, present in 85–90% of cases, together with chronic diarrhea, right-sided heart valve disease and pellagra-like skin damage caused by niacin (vitamin B3) deficiency. At Haute-Derma, accurately recognizing the pattern of facial flushing and the skin changes of niacin deficiency is key to steering the medical diagnosis, coordinating control of the NET and using light-based treatments to repair the facial blood vessels.
Pathogenesis: Vascular and Metabolic Skin Changes
The skin findings in carcinoid syndrome result from two parallel biological mechanisms:
- Flushing Caused by Vasomotor Effects:
- Serotonin and tachykinins (substance P, neurokinin A): These act directly on the smooth muscle of superficial vessels in the face, neck and upper chest, where superficial capillaries are densest, causing sudden vasodilation, increased microcirculatory blood flow and episodes of redness and heat.
- Histamine and bradykinin: Released mainly by gastric NETs, they cause flushing with hive-like plaques, watery eyes and itching.
- Chronic vasomotor change: Repeated vasodilation leads to permanent, tortuous dilated capillaries (telangiectasia) and cyanosis (a bluish tinge to the central face) from sluggish flow in the superficial veins.
- Niacin Deficiency Causing a Pellagra-Like Rash:
- Normally, only about 1% of dietary tryptophan is converted to serotonin; most of the rest goes through the kynurenine pathway to make niacin (vitamin B3) and proteins.
- In carcinoid patients, the tumor consumes up to 60% of the body's tryptophan to churn out serotonin. This diversion of tryptophan causes severe niacin deficiency and a pellagra-like rash: thickened, scaly dermatitis with dusky redness and peeling on sun-exposed skin (the neck and backs of the hands — the "Casal necklace" sign).
Types of Flushing by Tumor Origin
| Flushing Type | Main Mediators | Clinical Appearance on the Skin |
|---|---|---|
| Type I (brief) | Serotonin, tachykinins | Bright red face and upper chest lasting 2–5 minutes, with a feeling of heat; no scarring or color change after the episode. |
| Type II (dusky / cyanotic) | Persistently high serotonin | Deep red turning bluish (cyanotic flushing), with permanent fine telangiectasias on the nose and cheeks. |
| Type III (patchy) | Histamine | Large, patchy red areas with raised edges and marked itching, plus watery eyes, runny nose and low blood pressure. |
| Type IV (prolonged) | Histamine, vasoactive peptides | Redness lasting hours to days, with facial swelling, watery eyes and profuse sweating. |
Biochemical Diagnosis and Screening at Haute-Derma
Gold-Standard Biochemical Tests (5-HIAA and Chromogranin A)
- 24-hour urine 5-hydroxyindoleacetic acid (5-HIAA): 5-HIAA is the main breakdown product of serotonin. A raised level (> 15 mg/24 h) confirms the diagnosis of carcinoid syndrome. (Avoid bananas, avocado, pineapple and walnuts for 48 hours before collecting the sample.)
- Serum chromogranin A (CgA): reflects the overall neuroendocrine tumor burden.
Skin Examination and Dermoscopy: We assess the extent of fixed facial telangiectasia and look for the dark, rough pellagra-like dermatitis on the neck (Casal necklace) and forearms.
Nuclear Medicine Imaging and Echocardiography
- Somatostatin receptor scintigraphy (OctreoScan) or ⁶⁸Ga-DOTATATE PET/CT: Locates the primary tumor and any liver metastases.
- Echocardiography: Essential screening for carcinoid heart disease, in which high serotonin levels cause fibrosis of the tricuspid and pulmonary valves.
Coordinated Medical Management and Skin Repair at Haute-Derma
Treating carcinoid syndrome requires close coordination between systemic endocrine therapy and light-based treatment of the skin:
Systemic Control
- Somatostatin Analogs (SSAs):
- Octreotide (LAR) or lanreotide: Given as regular injections, these bind SSTR2 receptors on the tumor cells and block the release of serotonin and vasodilating peptides, reducing the frequency and intensity of flushing episodes by 85%.
- Serotonin Synthesis Inhibitor (Telotristat Ethyl): Used when flushing and diarrhea are not fully controlled by SSAs.
- Nutritional Treatment of Pellagra: High-dose niacinamide (vitamin B3), 100–500 mg/day, reverses the hyperkeratotic dermatitis and restores the epidermal barrier.
Light-Based Facial Repair at Haute-Derma
Once serotonin levels are under control with endocrine medication, Haute-Derma treats the vascular and pigment changes on the face:
- Clearing Fixed Telangiectasia with Long-Pulse Nd:YAG 1064 nm Laser and Vascular-Filter IPL:
- How it works: The 1064 nm long-pulse wavelength and the 560–590 nm IPL band are selectively absorbed by oxyhemoglobin inside the vessels. The resulting heat coagulates and collapses the dilated, tortuous capillary walls on the nose and cheeks without harming the surrounding tissue.
- Course: 3–5 sessions, 4–6 weeks apart.
- Nourishing the Skin and Restoring the Lipid Barrier:
- Iontophoresis with 5% niacinamide, ceramides and hyaluronic acid soothes the skin and repairs the lipid barrier damaged by repeated flushing.
- A broad-spectrum mineral sunscreen (zinc oxide) is essential to protect the sensitive skin from UV light.
