Catamenial Pneumothorax: Symptoms, Types, Causes and Treatment

Catamenial pneumothorax is a rare but significant condition affecting women, often presenting as an unexpected collapse of the lung around the time of menstruation. Understanding this syndrome is crucial for early diagnosis and effective management, as it can be easily overlooked or misdiagnosed. In this article, we will explore the symptoms, types, causes, and treatments of catamenial pneumothorax, synthesizing the latest research to provide a comprehensive and practical guide for patients, clinicians, and anyone interested in women's respiratory health.

Symptoms of Catamenial Pneumothorax

Most women with catamenial pneumothorax experience symptoms that overlap with other lung conditions, which can make diagnosis challenging. However, the timing and pattern of these symptoms—occurring in relation to the menstrual cycle—are key clues. Let's explore what to watch for.

Symptom	Timing	Frequency/Side	Source(s)
Chest pain	Perimenstrual	Right > Left	2346
Shortness of breath	Perimenstrual	Recurrent, often right-sided	23469
Shoulder/scapular pain	Perimenstrual	Sometimes precedes pneumothorax	123
Cough	Perimenstrual	Less frequent	412
Hemoptysis	Perimenstrual	Rare	312

Table 1: Key Symptoms

Understanding the Symptom Pattern

The hallmark of catamenial pneumothorax is its relationship to the menstrual cycle—symptoms typically appear within 24 hours before and up to 72 hours after the onset of menstruation 2694. This temporal association is crucial for distinguishing it from other causes of spontaneous pneumothorax.

The Most Common Presentations

• Chest pain is the most frequently reported symptom, often described as sudden and severe, and localized to the right side of the chest. This is followed by shortness of breath (dyspnea), which can range from mild to severe 23469.
• Some women also report shoulder or scapular pain, which may precede the pneumothorax by several cycles, serving as an early warning sign 123.
• Less commonly, cough and in rare cases, hemoptysis (coughing up blood) can occur, especially if there is endometrial tissue involvement of the airways 312.

Why Symptoms Are Often Overlooked

Because these symptoms are non-specific and overlap with many more common respiratory conditions, catamenial pneumothorax is frequently underdiagnosed. Many women may be evaluated for asthma, pneumonia, or anxiety before the correct diagnosis is made. The key distinguishing feature remains the cyclical nature of the symptoms in relation to menstruation.

Types of Catamenial Pneumothorax

Catamenial pneumothorax is not a one-size-fits-all condition. It varies in presentation and underlying mechanism, and can be classified in several ways to guide diagnosis and management.

Type	Main Feature	Prevalence/Side	Source(s)
Classical CP	Perimenstrual onset	Right-side (85–95%)	23610
Non-classical (TERP)	Not always cyclical	May be right, left, or bilateral	5678
With endometriosis	Thoracic/pelvic foci	Associated with endometriosis	1361013
Without endometriosis	No endometrial tissue found	Often idiopathic	1015

Table 2: Types of Catamenial Pneumothorax

Classical Catamenial Pneumothorax

This is the most recognized form—recurrent spontaneous pneumothorax that occurs within 24 hours before to 72 hours after the onset of menstruation. It almost always affects the right lung (in over 85–95% of cases), and is frequently associated with diaphragmatic or thoracic endometriosis 23610.

Non-classical (Thoracic Endometriosis-Related Pneumothorax, TERP)

Not all cases are strictly tied to menstruation. Some women experience non-catamenial thoracic endometriosis-related pneumothorax (TERP), where episodes of lung collapse occur outside the perimenstrual window. These cases may involve left-sided or even bilateral pneumothorax, and are more commonly seen in women with endometriosis 5678.

With and Without Endometriosis

In many patients, thoracic or pelvic endometriosis is confirmed through imaging or surgical exploration 1361013. However, in a significant minority, no endometrial tissue is found, making their pneumothorax "idiopathic" or of unclear cause 1015. This distinction is important for prognosis and treatment planning.

Other Variants

Rare cases involve left-sided or bilateral pneumothoraces, and a few have been attributed to endometrial implants in unusual locations, such as the visceral pleura or lung parenchyma, rather than the diaphragm 813.

Causes of Catamenial Pneumothorax

Understanding the mechanisms behind catamenial pneumothorax helps guide both diagnosis and management. While the exact cause is multifactorial and sometimes elusive, several key theories and risk factors have emerged from research.

Cause/Theory	Key Feature	Evidence/Notes	Source(s)
Thoracic endometriosis	Endometrial tissue in chest	Diaphragmatic and pleural lesions; often right-sided	1236101314
Diaphragmatic defects	Fenestrations/holes in diaphragm	Air passage from abdomen to chest	10131416
Hormonal influences	Menstrual cycle-related changes	Estrogen/progesterone effects on endometrial tissue	16910
Air passage via genital tract	Uterine-tubal-diaphragm route	Rare, possible in some cases	1314
Previous pelvic surgery	Increased risk	Uterine procedures, infertility	12

Table 3: Main Causes and Theories

Thoracic Endometriosis

The most widely supported cause is the presence of ectopic endometrial tissue in the thoracic cavity (thoracic endometriosis). This tissue responds to hormonal changes during the menstrual cycle, leading to local inflammation, bleeding, and sometimes small holes or nodules in the diaphragm or pleura. These changes create a pathway for air to enter the chest cavity, causing lung collapse 1236101314.

Diaphragmatic Defects

Many women with catamenial pneumothorax have small fenestrations (holes) or nodules in the diaphragm, which can be seen during thoracic surgery. These lesions allow air from the abdomen or peritoneal cavity to pass into the chest, especially during menstruation when endometrial tissue may become more active or fragile. The right side is more commonly affected, possibly due to anatomical differences and the protective effect of the heart and pericardium on the left diaphragm 10131416.

Hormonal and Other Contributing Factors

Fluctuations in estrogen and progesterone during menstruation are thought to trigger the activity of endometrial tissue and weaken diaphragmatic tissue, increasing susceptibility to pneumothorax 16910. Some studies have found that previous pelvic surgery and a history of infertility are strong risk factors, supporting a link between pelvic endometriosis and thoracic involvement 12.

Alternative Theories

Rare cases have been linked to direct passage of air from the genital tract through the uterus and fallopian tubes, into the abdominal cavity, and through diaphragmatic defects into the chest (the so-called "transgenital route") 1314. Others may involve primary lung pathology, such as bullae or blebs, especially in cases without clear endometriosis 810.

Treatment of Catamenial Pneumothorax

Treating catamenial pneumothorax requires a multidisciplinary approach, as recurrence is common without comprehensive care. Management usually combines surgical and hormonal therapies tailored to the individual's case.

Treatment	Purpose/Action	Recurrence Risk	Source(s)
Surgery (VATS, thoracotomy)	Remove lesions, repair diaphragm, pleurodesis	Reduced if combined with hormonal therapy	1014151617
Hormonal therapy (GnRH agonists, OCPs)	Suppress menses/endometrial activity	Lower with GnRH agonists	101617
Pleurodesis/Pleurectomy	Fuse pleural layers/prevent recurrence	Not always sufficient alone	151617
Diaphragmatic repair/mesh	Close defects, prevent air passage	Best outcomes when performed	1014151617

Table 4: Main Treatment Approaches

Surgical Management

Surgical intervention is the mainstay of treatment. The most common approach is video-assisted thoracoscopic surgery (VATS), which allows for:

• Identification and removal of endometrial lesions and nodules
• Repair or reinforcement of diaphragmatic defects (using sutures or synthetic mesh)
• Pleurodesis (chemical or mechanical) or pleurectomy to prevent future lung collapse 1014151617

Success rates are highest when all visible lesions are addressed and the diaphragm is systematically inspected and reinforced, even if it appears normal 1516.

Hormonal Therapy

Hormonal suppression aims to reduce or eliminate menstruation, thereby decreasing the activity of endometrial tissues. Two main options:

• Gonadotropin-releasing hormone (GnRH) agonists: Highly effective in preventing recurrences, as they induce a temporary menopause-like state 101617.
• Oral contraceptives or estrogen-progesterone therapy: Less effective, with higher recurrence rates than GnRH agonists 1617.

Hormonal therapy is often used in combination with surgery, especially in women with confirmed endometriosis or high risk of recurrence.

Pleurodesis and Diaphragmatic Repair

While pleurodesis (fusing the pleural layers) can help prevent recurrence, it is often insufficient on its own if diaphragmatic defects are not addressed. Best outcomes are seen when pleurodesis is combined with direct repair or covering of diaphragmatic holes using mesh 151617.

Multidisciplinary and Long-term Care

Optimal management involves a team approach, including thoracic surgeons, gynecologists, and pulmonologists. Close follow-up is essential, as recurrence rates remain significant (up to 30–40%), particularly if treatment is incomplete or hormonal therapy is not used 917.

Conclusion

Catamenial pneumothorax remains a challenging and often under-recognized condition. Awareness of its unique features and optimal management strategies can greatly improve outcomes for affected women.

Key Points:

• Catamenial pneumothorax is characterized by recurrent episodes of lung collapse linked to menstruation, most commonly affecting the right side.
• Symptoms include chest pain, shortness of breath, and sometimes shoulder pain, with a clear temporal relationship to menstrual cycles.
• The main causes are thoracic endometriosis and diaphragmatic defects, often exacerbated by hormonal changes during menstruation.
• Treatment is most effective when it combines surgical management (VATS, diaphragmatic repair, pleurodesis) with hormonal suppression (preferably GnRH agonists).
• Multidisciplinary care and long-term follow-up are essential to minimize recurrences and improve quality of life.

By recognizing the distinct pattern of catamenial pneumothorax and providing targeted, evidence-based care, clinicians can make a meaningful difference for women facing this rare but impactful condition.