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Zollinger‑Ellison Syndrome – Atypical Presentation

Overview

Zollinger‑Ellison syndrome (ZES) is a rare disorder caused by gastrin‑producing neuroendocrine tumors (also called gastrinomas) that most often arise in the pancreas or duodenum. The excess gastrin stimulates the stomach to secrete large amounts of gastric acid, leading to severe ulcers and a spectrum of gastrointestinal (GI) and systemic symptoms.

Although the classic textbook description focuses on recurrent, refractory peptic ulcers, atypical presentations—such as chronic diarrhea, malabsorption, or even non‑GI complaints—are increasingly recognized, especially in patients with small, non‑functioning tumors or those with coexisting conditions that mask classic ulcer disease.

Who it affects

• Both sexes equally; slight male predominance (≈55 %).
• Median age at diagnosis: 45–55 years, but atypical cases can appear in adolescents or older adults.
• About 25 % occur as part of the hereditary syndrome multiple endocrine neoplasia type 1 (MEN‑1).

Prevalence

• Incidence: 0.5–2 cases per million persons per year [1].
• Overall prevalence is estimated at 1–3 per 100,000, making it one of the rarer neuroendocrine tumor syndromes.

Symptoms

Symptoms result primarily from hyperacidic gastric secretions and the tumor’s local effects. In atypical presentations, the classic ulcer‑related pain may be minimal or absent.

Typical (classic) symptoms

• Refractory peptic ulcer disease – often multiple ulcers beyond the duodenum, including the jejunum.
• Epigastric burning pain – worsens with meals, may be relieved by antacids.
• Acid‑related gastro‑esophageal reflux disease (GERD).

Atypical / extra‑ulcer symptoms

• Chronic watery diarrhea – occurs in up to 40 % of patients; may be secretory.
• Steatorrhea (fatty stools) – due to acid‑induced inactivation of pancreatic enzymes.
• Weight loss & malnutrition – secondary to malabsorption.
• Gastrointestinal bleeding – from ulcer erosion; may present as melena or occult blood.
• Upper‑GI obstruction – rare, due to large tumor mass.
• Non‑GI manifestations:
  • Hypokalemia & metabolic alkalosis (from chronic vomiting/diarrhea).
  • Carcinoid‑type flushing or itching (if tumor secretes other peptides).
  • Fatigue, anemia, and bone pain (secondary to chronic blood loss or vitamin deficiencies).

Causes and Risk Factors

ZES is fundamentally a gastrinoma‑driven disease.

Primary cause

• Neuroendocrine tumor (gastrinoma) producing excessive gastrin.

Risk factors

• MEN‑1 syndrome – germline mutations in the MEN1 gene; accounts for ~25 % of cases.
• Family history of gastrinomas or MEN‑1.
• Previous diagnosis of a pancreatic or duodenal neuroendocrine tumor.
• Chronic atrophic gastritis or H. pylori infection are NOT risk factors for ZES, but can coexist and confound presentation.

Diagnosis

Diagnosing atypical ZES requires a high index of suspicion, especially when ulcer disease is absent.

Step‑wise approach

1. Clinical suspicion – persistent diarrhea, refractory ulcer disease, or unexplained high gastric acidity.
2. Biochemical testing
   • Fasting serum gastrin – > 1000 pg/mL (normal < 100 pg/mL) is highly suggestive; values 2–3× upper limit with gastric pH < 2 are also diagnostic.
   • Secretin stimulation test – paradoxical rise in gastrin after IV secretin (≥ 120 pg/mL increase) is the gold standard when fasting gastrin is borderline.
   • Assess gastric pH (often < 2) and rule out chronic proton‑pump inhibitor (PPI) use that can elevate gastrin.
3. Imaging to locate the tumor
   • Somatostatin receptor scintigraphy (SRS) / 68Ga‑DOTATATE PET‑CT – highest sensitivity (≈ 90 %).
   • Multiphasic CT or MRI of the abdomen – identifies pancreatic or duodenal lesions > 1 cm.
   • Endoscopic ultrasound (EUS) – excellent for small (< 2 cm) duodenal tumors.
4. Endoscopy – upper‑GI endoscopy reveals multiple ulcers, often beyond the duodenum; biopsies rule out H. pylori or malignancy.
5. Genetic testing – indicated if MEN‑1 is suspected (family history, other endocrine tumors).

Treatment Options

Management combines acid suppression, tumor control, and symptom relief.

Medical therapy

• Proton‑pump inhibitors (PPIs) – high‑dose (e.g., omeprazole 60 mg bid or esomeprazole 40 mg bid). PPIs are the cornerstone, normalizing gastric pH and allowing ulcer healing.
• H2‑receptor antagonists – may be added for breakthrough symptoms but are less effective than PPIs.
• Somatostatin analogs (e.g., octreotide, lanreotide) – reduce gastrin secretion and can shrink tumors, especially in MEN‑1 patients.
• Chemotherapy / targeted therapy – reserved for metastatic or unresectable disease (e.g., everolimus, sunitinib).

Surgical options

• Curative resection – enucleation or pancreaticoduodenectomy for localized tumors; offers the best long‑term prognosis.
• Debulking surgery – for metastatic disease to reduce tumor load and hormone production.
• Radiofrequency ablation or hepatic artery embolization – used for liver metastases.

Lifestyle and supportive care

• Small, frequent meals low in fat to reduce acid load.
• Avoid smoking, alcohol, NSAIDs, and caffeine, which aggravate ulcer disease.
• Supplement fat‑soluble vitamins (A, D, E, K) if malabsorption is present.
• Maintain adequate hydration and electrolytes, especially if diarrhea is prominent.

Living with Zollinger‑Ellison syndrome – atypical presentation

Even when classic ulcer pain is absent, the disease can affect daily life. Below are practical strategies.

Eating & Nutrition

• Consume low‑acid foods (e.g., oatmeal, bananas, boiled vegetables) and avoid citrus, tomato‑based sauces, and spicy foods.
• Incorporate medium‑chain triglyceride (MCT) oil if steatorrhea is severe; MCTs are absorbed without pancreatic lipase.
• Track stool frequency and consistency; a daily log helps clinicians adjust medications.

Medication adherence

• Take PPIs 30 minutes before breakfast and dinner; missing doses can precipitate ulcer bleeding.
• Set reminders for somatostatin analog injections (often monthly).

Monitoring & Follow‑up

• Schedule serum gastrin and gastric pH checks every 6–12 months.
• Annual imaging (CT/MRI or DOTATATE PET) to detect recurrence or metastasis.
• Report new symptoms promptly—especially worsening diarrhea, GI bleeding, or abdominal pain.

Psychosocial aspects

• Join support groups (e.g., The Neuroendocrine Tumor Research Foundation) to share experiences.
• Consider counseling if chronic illness impacts mood or work life.

Prevention

Because ZES originates from sporadic tumor development, primary prevention is limited, but risk can be mitigated:

• Genetic counseling for families with known MEN‑1 mutations; early screening with fasting gastrin and imaging can detect gastrinomas before symptom onset.
• Regular medical surveillance for patients with other neuroendocrine tumors.
• Avoid chronic use of medications that increase gastric gastrin (e.g., long‑term PPIs in otherwise healthy individuals) – though they are essential once ZES is diagnosed.

Complications

If untreated or poorly controlled, ZES can lead to serious health problems:

• Perforated peptic ulcer – surgical emergency with high morbidity.
• Upper GI bleeding – may require endoscopic therapy or transfusion.
• Gastric entero‑chromaffin‑like (ECL) cell hyperplasia → gastric carcinoids.
• Severe malabsorption → deficiencies in iron, calcium, vitamin B12, and fat‑soluble vitamins.
• Metastatic disease – liver, lymph nodes, or distant sites; worsens prognosis.
• Electrolyte disturbances – hypokalemia, metabolic alkalosis from chronic diarrhea/vomiting.

When to Seek Emergency Care

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Sources:

1. American College of Gastroenterology. Clinical guideline: Management of patients with Zollinger‑Ellison syndrome. Gastroenterology. 2022.
2. Mayo Clinic. Zollinger‑Ellison Syndrome. Accessed June 2024.
3. National Institutes of Health (NIH). Neuroendocrine Tumors. 2023.
4. Cleveland Clinic. Zollinger‑Ellison Syndrome. 2023.
5. World Health Organization. Neuroendocrine Tumours Fact Sheet. 2022.

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