What is the pathophysiology of Asherman's syndrome?

Pathophysiology of Asherman's Syndrome

Asherman's syndrome develops when trauma to the pregnant uterus—most commonly from curettage—destroys the endometrial basalis layer and disrupts the endometrial stem cell niche, triggering an inflammatory cascade that leads to defective healing, fibrosis, and intrauterine adhesion formation rather than normal endometrial regeneration. 1, 2

Primary Mechanism: Endometrial Destruction and Stem Cell Niche Disruption

• Trauma to the basalis layer is the critical initiating event, as this layer contains the endometrial stem cells necessary for cyclic regeneration 1, 2
• Curettage of the pregnant uterus represents the highest-risk scenario because the gravid endometrium is particularly vulnerable to deep injury that extends beyond the functionalis into the basalis 1, 3
• Post-partum transarterial uterine artery embolization carries up to a 12% risk of developing uterine synechiae, representing another iatrogenic pathway 4

Inflammatory Cascade and Defective Healing

• All etiologies of Asherman's syndrome share an underlying inflammatory mechanism that leads to defective endometrial healing and vascularization 1
• The inflammatory response following endometrial injury triggers excessive fibrosis and collagen deposition rather than normal epithelial regeneration 5
• Nuclear factor-kappa beta (NF-κB) expression is significantly increased in Asherman's syndrome, reflecting the persistent inflammatory state 5
• Suppression of angiogenesis occurs, as evidenced by decreased vascular endothelial growth factor (VEGF) expression in affected endometrium 5

Fibrotic Transformation

• Intrauterine adhesions form from fibrotic changes within the uterine tract, replacing normal endometrial tissue with scar tissue 6, 5
• The endometrium becomes significantly thinned with degeneration of the endometrial epithelium 5
• Proliferative capacity is markedly reduced, as demonstrated by decreased proliferating cell nuclear antigen (PCNA) expression 5

Genetic Predisposition Component

• Distinct genetic profiles have been observed in the endometrium of Asherman's syndrome patients, suggesting the condition may not be purely iatrogenic 1
• Some cases occur without any prior surgical procedures (idiopathic cases), supporting a constitutional predisposition to intrauterine adhesion formation 1
• Cases associated with congenital uterine abnormalities further suggest an underlying genetic susceptibility 1

Two Pathophysiologic Mechanisms of Menstrual Dysfunction

• Reduction of the endometrial bleeding area from adhesions physically decreases the surface available for menstruation 7
• Trophic changes and hormonal unresponsiveness of the remaining endometrium occur, possibly from a visceral reflex originating at the internal os 7
• When amenorrhea results from cervical stenosis or atresia, the ovarian cycle continues but the endometrium becomes refractory to hormonal stimuli—notably, hematometra does not occur in these cases 7

Puerperal Period as High-Risk Window

• Asherman's syndrome developing within the puerperal period has worse outcomes than disease developing outside this window, with an 86.3% adhesion reformation rate versus 38.6% in non-puerperal cases 8
• The puerperal endometrium appears particularly susceptible to severe and treatment-resistant adhesion formation 8

Clinical Manifestation Pathway

• The syndrome manifests through menstrual irregularities, pelvic pain, and infertility resulting from the combination of reduced functional endometrium and mechanical obstruction 6
• Obstetrical complications including recurrent pregnancy loss, placenta abnormalities, preterm birth, and intrauterine growth retardation occur due to inadequate endometrial support 6
• Up to 44% of patients experience symptom recurrence within 12 months after adhesiolysis, reflecting the persistent underlying pathophysiology 4