Peutz-Jeghers syndrome (PJS) is a rare, autosomal dominant hereditary polyposis disorder defined clinically by the association of characteristic mucocutaneous melanin pigmentation and widespread gastrointestinal hamartomatous polyps^1,3. First described comprehensively by Johannes Peutz in 1921 and further characterized by Harold Jeghers in 1949, the condition arises from germline loss-of-function pathogenic variants in the STK11 (serine/threonine kinase 11, also designated LKB1) tumor suppressor gene located on chromosome 19p13.3^2,4. Although hamartomatous polyps can develop anywhere throughout the gastrointestinal tract—most predominantly in the small intestine—they pose severe mechanical risks, including recurrent abdominal pain, chronic blood loss resulting in iron-deficiency anemia, and small-bowel intussusception frequently requiring emergency surgical intervention^1,6. Furthermore, PJS is recognized as a profound cancer predisposition syndrome, conferring significantly elevated lifetime cumulative risks for malignancies of both the gastrointestinal tract and extraintestinal organs, including the pancreas, breast, lung, uterus, cervix, ovaries, and testicles (such as sex cord tumors with annular tubules)^1,5. Modern management relies on advanced device-assisted enteroscopy, magnetic resonance enterography, and structured multidisciplinary surveillance protocols designed to mitigate acute surgical emergencies and detect neoplastic transformation at an early, curable stage^1,3.

Etiology & Risk Factors

• Genetic Basis & Inheritance: PJS is inherited in an autosomal dominant pattern with high penetrance, though approximately 25% of cases represent de novo germline mutations in the absence of a documented family history^1,7.
• Causative Gene: Pathogenic variants, deletions, or structural rearrangements of the STK11/LKB1 gene (19p13.3), which encodes a master serine/threonine kinase regulating cellular energy metabolism, polarity, and cell cycle arrest, account for 80% to 90% of clinical cases^2,7.
• Phenotypic Variability: Variable expressivity is a hallmark of the syndrome; family members carrying identical STK11 mutations can display widely differing polyp burdens, ages of onset, and extraintestinal tumor manifestations^3,5.
• Demographics & Prevalence: Estimated prevalence ranges between 1 in 50,000 and 1 in 200,000 live births, with equal distribution among sexes and no specific racial predilection^1,2.
• Extraintestinal Malignancy Risk Factors: Cumulative lifetime cancer risks approach 85% to 93% by age 70, driven by the systemic tumor-suppressive functions of LKB1 across multiple epithelial and endocrine tissues^1,5.

Pathophysiology

The molecular pathogenesis of Peutz-Jeghers syndrome is rooted in the disruption of the STK11/LKB1 tumor suppressor pathway. LKB1 functions as an upstream master kinase that phosphorylates and activates AMP-activated protein kinase (AMPK), as well as at least 13 other downstream kinases related to AMPK. This regulatory network controls cellular energy homeostasis, polarity, and growth arrest via suppression of the mechanistic target of rapamycin (mTOR) signaling cascade. In PJS, germline inactivation of one STK11 allele followed by somatic inactivation or loss of heterozygosity of the remaining wild-type allele in mucosal cells initiates tumorigenesis. Unlike classic adenomas driven primarily by APC/beta-catenin pathways, Peutz-Jeghers polyps are hamartomas characterized by exuberant, disorganized growth of normal mucosal elements—epithelium, lamina propria, and a distinctive, arborizing core of smooth muscle arising directly from the muscularis mucosae. This smooth muscle scaffolding distinguishes PJS polyps histologically from juvenile and hyperplastic polyps. As these hamartomas enlarge within the narrow lumen of the small bowel, peristaltic drag exerts traction on the mobile mesenteric loops, precipitating mechanical lead-point intussusception, bowel wall ischemia, lymphatic obstruction, and intermittent colicky obstruction. Concurrently, chronic mucosal ulceration over the polyp surface leads to insidious micro-hemorrhage and profound chronic iron-deficiency anemia.

Clinical Presentation & Classic Clinical Signs

• History & Cardinal Symptoms:
  • Intermittent Colicky Abdominal Pain: Caused by transient or complete small-bowel intussusception, often resolving spontaneously when the bowel reduces or persisting until surgical/endoscopic intervention is performed^1,3.
  • Gastrointestinal Bleeding: Manifests as overt melena, hematochezia, or occult blood loss leading to chronic fatigue, weakness, and severe microcytic iron-deficiency anemia^1,3.
  • Nausea, Vomiting, and Abdominal Distension: Secondary to high-grade mechanical obstruction or recurrent small-bowel intussusceptions^3,6.
  • Childhood Onset: Cutaneous and mucosal pigmentation typically appears in infancy or early childhood, whereas symptomatic gastrointestinal polyposis frequently presents during late childhood, adolescence, or early adulthood (median age of first intussusception around 10 to 20 years)^3,5.
• Physical Examination & Named Clinical Signs:
  • Mucocutaneous Melanocytic Macules: Small (1 to 5 mm), flat, dark brown to blue-black pigmented spots distributed pathognomonically across the vermilion border of the lips, buccal mucosa, hard palate, perioral skin, fingers, toes, and perineum^1,3. Buccal mucosal involvement is highly specific for PJS and helps differentiate these lesions from ordinary freckles (ephelides) or Peutz-Jeghers-like syndromes^3,5.
  • Testicular Masses / Gynecomastia: In male patients, large-cell calcifying Sertoli cell tumors can secrete estrogen or inhibit testosterone synthesis, leading to gynecomastia, advanced bone age, and palpable testicular masses^1,5.
  • Pelvic / Ovarian Masses: Female patients may develop sex cord tumors with annular tubules (SCAT), occasionally presenting with precocious pseudopuberty, irregular vaginal bleeding, or pelvic fullness^1,5.

Diagnostic Workup & Interpretation (Laboratory, Imaging & ECG/Pathology)

Staging, Classification & Clinical Scoring Systems

Differential Diagnosis

Management & Treatment Protocol

• Initial Stabilization & Resuscitation:
  • Patients presenting with acute abdomen, signs of small-bowel obstruction, or acute intussusception require immediate surgical consultation, aggressive fluid resuscitation with isotonic crystalloids (e.g., lactated Ringer's solution at 15–20 mL/kg bolus adjusted to hemodynamic response), nasogastric tube decompression, and serial abdominal examinations^1,3.
  • Transfusion of packed red blood cells (PRBCs) to maintain hemoglobin > 7.0 g/dL (or > 9.0 g/dL in patients with cardiovascular disease) in the setting of acute or chronic gastrointestinal hemorrhage associated with iron deficiency^1,3.
• First-Line Medical / Pharmacological Therapy (with exact adult dosing):
  • Iron Replacement Therapy: Oral ferrous sulfate 325 mg (delivering 65 mg elemental iron) orally three times daily for mild iron-deficiency anemia, or intravenous iron sucrose (e.g., 200–300 mg IV infused slowly in 100 mL 0.9% NaCl over 1.5 to 2.5 hours, repeated weekly to replete total iron deficit) for significant ongoing blood loss or intolerance to oral iron preparations^1,3.
  • Prophylactic Symptom Management: No targeted disease-modifying chemotherapeutic agent currently reverses STK11 germline mutation effects; management centers strictly on endoscopic clearance and surveillance^2,7.
• Surgical / Interventional Indications:
  • Device-Assisted Enteroscopy (DAE): Double-balloon enteroscopy (DBE) or single-balloon enteroscopy (SBE) represents the gold-standard therapeutic intervention, enabling complete visualization of the small bowel and endoscopic snare polypectomy of all polyps measuring ≥ 1.0 to 1.5 cm to eliminate the risk of intussusception and bleeding^1,3.
  • Laparoscopic / Intraoperative Enteroscopy: Reserved for cases complicated by irreducible intussusception, bowel ischemia, perforation, or massive polyp burden inaccessible via standard device-assisted enteroscopy, combining segmental bowel resection with intraoperative enteroscopic polypectomy ("clean-sweep" approach) to preserve maximal bowel length and prevent short-bowel syndrome^1,3.
  • Structured Surveillance Protocol: Commencing around age 8 to 10 years, surveillance includes baseline upper endoscopy (EGD), colonoscopy, and magnetic resonance enterography (MRE) or small-bowel capsule endoscopy, repeated every 2 to 3 years. Pancreatic surveillance (via endoscopic ultrasonography [EUS] or MRI/MRCP) and breast surveillance (annual magnetic resonance imaging [MRI] and mammography starting at age 25 to 30) are instituted according to established international guidelines^1,3.

Complications & Prognosis

• Acute Complications: Small-bowel intussusception (the most common surgical emergency, occurring in up to 50% of patients by age 20), high-grade bowel obstruction, bowel infarction, ischemia, and acute or chronic severe gastrointestinal hemorrhage leading to hemodynamic instability^1,3.
• Chronic & Malignant Complications: Development of gastrointestinal carcinomas (colorectal, gastric, small bowel) and extraintestinal malignancies, notably pancreatic adenocarcinoma, breast cancer, ovarian sex cord tumors, cervical adenoma malignum, and testicular Sertoli cell tumors^1,5.
• Prognosis & Survival: Overall life expectancy is moderately reduced compared to the general population, primarily dictated by the development of visceral malignancies and complications from recurrent bowel resections. Adherence to structured multidisciplinary surveillance significantly reduces morbidity, prevents emergency laparotomies, and improves long-term survival outcomes^1,3.