A Case Report of Congenitally Absent Pericardium Masquerading as Recurrent Pericarditis

Abstract

A 24-year-old female with a history of Swyer-James-MacLeod syndrome presented with acute onset of pleuritic chest pain and was initially diagnosed with acute pericarditis. The 12-lead electrocardiogram demonstrated typical diffuse ST-segment elevation and PR-segment depression. Symptoms resolved rapidly with anti-inflammatory therapy consisting of ibuprofen and colchicine. After completing a 3-month course of the latter, her symptoms rapidly recurred. Workup, including labs and cardiac imaging consisting of a transthoracic echocardiogram and cardiac magnetic resonance imaging, was initially interpreted as normal. Re-review of her cardiac imaging revealed the patient had signs of a congenitally absent pericardium, including a “Snoopy Sign” on her posterior-anterior chest X-ray, which is characterized by levoposition of the cardiac silhouette, a lucent area between the pulmonary artery and aorta because of the presence of lung tissue, a lucent area between the base of the heart and the left hemidiaphragm, loss of the right heart border, a prominent pulmonary artery, and a flattened and elongated left ventricular contour. The patient had a cardiac computed tomography scan, which confirmed the diagnosis. In conclusion, a congenitally absent pericardium is a rare disorder, often undetected or misdiagnosed. There are characteristic findings on imaging such as a “Snoopy Sign” on a posterior-anterior chest X-ray, which can be easily missed because of its rarity. Our goal of this report is to educate health care providers about this rare disorder.

Introduction

A congenitally absent pericardium is a rare disorder often found incidentally during thoracic surgery, imaging studies, or postmortem examination because it is generally asymptomatic,¹ though has been reported to present with chest pain, prominent cardiac pulsation, or sudden death from herniation of cardiac tissue through partial pericardial defects.² Although exact prevalence is difficult to determine, estimated prevalence ranges from 0.0001% to 0.044%.³ Familial inheritance is rare and no association with medication exposure or underlying infection for pathogenesis has been identified.⁴ As majority of providers are not aware of this extremely rare disorder, symptomatic patients can be mistaken for other cardiac conditions such as ischemic heart disease, aortic dissection, pulmonary embolism, or acute pericarditis. This may lead to inappropriate treatments or diagnostic testing which can be problematic in the era of patient safety. Imaging studies including electrocardiogram (EKG), chest X-Ray, echocardiogram, cardiac computed tomography (CT) and cardiac magnetic resonance imaging (MRI) may aid in the diagnosis and timely treatment of such a condition, however currently no clear guideline for diagnosis or treatment exists. We present a case of congenitally absent pericardium which was initially mistaken for recurrent pericarditis. We aim to educate healthcare providers about this rare disease to reduce misdiagnosis and suggest a potential therapeutic option.

Case Report

A 24-year-old female with history of Swyer-James-MacLeod syndrome (characterized by alveolar hyperdistention and loss of pulmonary vasculature due to obliteration of small airways secondary to bronchiolitis) presented to our clinic for evaluation of recurrent pericarditis.^5–7 She had pleuritic chest pain without identifiable triggers such as upper respiratory infections, new medications, previous radiation exposure, personal history of cancer, or Lyme disease. The patient denied any autoimmune disorder symptoms. Family history was non-contributory. Vital signs and full physical examination were unremarkable. Workup for infectious etiologies including tuberculosis, Coxsackie B, Parvo B19, human immunodeficiency virus (HIV) and, Hepatitis B and C were negative. Labs including anti-nuclear antibody (ANA), anti-neutrophil cytoplasmic antibody (ANCA), thyroid stimulating hormone (TSH), D-dimer, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) were normal. A 12-lead EKG showed diffuse ST-segment elevations and PR-segment depression without any pathologic Q waves, T wave inversions, or ST-segment depressions. A posterior-anterior chest X-ray showed no infiltrates or pleural effusions (Figure 1). Transthoracic echocardiogram showed normal left ventricular function without any pericardial effusion (Figure 2). The patient improved rapidly with ibuprofen and colchicine. However, her symptoms recurred soon after completing a 3-month course of colchicine. At this time, she was diagnosed with idiopathic recurrent pericarditis and was placed on an extended course of colchicine. A cardiac MRI did not reveal any pericardial gadolinium enhancement suggestive of pericarditis. Differential diagnosis included Familial Mediterranean Fever, Adult Onset Still's disease, or very early systemic lupus erythematosus, though were not felt to be likely. Repeat echocardiogram showed preserved left ventricular function with right ventricular dilatation. However, review of the echocardiogram images suggested the final diagnosis of a congenitally absent pericardium. Re-evaluating the chest X-ray revealed a “Snoopy sign”, which is pathognomonic for a congenitally absent pericardium. Further review of her previous images, as well as performance of a cardiac CT confirmed the diagnosis (Figure 3–5).

Figure 1.

Chest X-ray, posterior to anterior view. Leftward displaced heart, loss of right heart border, a lucent area between the left ventricle and left hemidiaphragm (white arrow), a lucent area between the pulmonary artery and aorta (blue arrow), and a flattened and elongated left ventricular contour (yellow arrow) are pathognomonic for a congenitally absent pericardium, previously described as the “Snoopy Sign.”

Figure 2.

Transthoracic Echocardiogram, apical 4-chamber view. Teardrop-shaped appearance of the heart with elongated atria and a bulbous left ventricle. The imaging may be technically difficult due to unusual acoustic windows as a result of cardiac levoposition.

Figure 3.

Cardiac CT shows area of pericardium (blue arrow) and area of absent pericardium (yellow arrow).

Figure 5.

Cardiac CT from a normal individual. Presence of pericardium along LV free wall (red arrow).

Discussion

A congenitally absent pericardium is a rare disorder often found incidentally while asymptomatic.¹ Failure of pleuropericardial membrane fusion is considered to be a cause of a congenitally absent pericardium.^8,9 This may occur when the heart enlarges before fusion of the pleuropericardial membrane.⁸ Another potential cause can be a tear induced by traction contributing to a defect in the pericardium.^8,10 Lastly, if the cardinal veins (duct of Cuvier) prematurely atrophy, a defective pericardium may form as a consequence of reduced blood supply.^8,11

In symptomatic patients, clinical features differ by the type of defects. The localized defects of pericardium often manifest as syncope, palpitations, or sudden death. Delayed onset of symptoms is a key feature for a totally absent pericardium and it is often accompanied by postural or nocturnal stabbing, or angina-like pain with variable intensities, although pathogenesis of the pain is unclear at this time.^1,3,12–17 Dyspnea and trepopnea (Dyspnea associated with unilateral lateral recumbent position) may be other manifestations.^1,3,4

Physical examination may reveal displacement of the apical impulse to the axilla or posterior chest, systolic ejection murmurs and an absence of precordial heart sounds.^1,3,12,18,19 A 12-lead EKG may show a combination of an incomplete right bundle branch block, right axis deviation and a displacement of transition zone to the left in the precordial leads.^1,3,19,20

Transthoracic echocardiogram, typically, cannot directly visualize the defect of pericardium. Due to an atypical cardiac positioning and orientation, it may be necessary to obtain more lateral and superior echocardiographic windows.^8,21,22 Abnormal wall motion, such as cardiac hypermobility is commonly present.^8,21,22 In addition, systolic movement of the ventricular septum may be flat or paradoxical despite having normal systolic thickening.^8,21,22 Since the heart is not fixated in the mediastinum, the left ventricle may have a teardrop-shaped appearance with an elongated atria and a bulbous left ventricle, which can be prominently seen on an apical four chamber view (Figure 3).^4,21,22 Echocardiography may also detect associated congenital cardiac defects, such as Tetralogy of Fallot, patent ductus arteriosus, bicuspid aortic valve and atrial septal defect.^4,8 Unfortunately, echocardiogram is not always diagnostic. However, when echocardiography is performed in several positions, such as the left lateral decubitus, the right lateral decubitus and the dorsal decubitus position, in combination with a 12-lead EKG, it may be used as a diagnostic tool.^18,23

A posterior-anterior chest X-ray may be characterized by levoposition (leftward and posterior displacement) of the cardiac silhouette, a lucent area between the pulmonary artery and aorta and/or a lucent area between the base of the heart and the left hemidiaphragm because of the presence of lung tissue, loss of the right heart border, a prominent pulmonary artery, and a flattened and elongated left ventricular contour, previously described as a “Snoopy Sign” (Figure 2).^{3,4,9,24–28}

The diagnostic image modality of choice is cardiac MRI.^8,29 The absence of the pericardium or the pre-aortic pericardial recess are key findings.^4,8 A congenitally absent pericardium may have extra-cardiac associations such as bronchogenic cyst, pulmonary sequestration, Marfan's syndrome, VATER syndrome, Pallister-Killian syndrome, and a syndrome of mental retardation, abnormal facies, and growth hormone deficiency.^4,24–26 There are several reported severe complications of a congenitally absent pericardium, such as myocardial ischemia, fatal myocardial strangulations and sudden death.^24,30

Since it is a rare disease, it may be easily missed or misdiagnosed. There are no standardized treatments but surgical reconstruction might be beneficial for controlling severe symptoms in patients refractory to medical therapy.³ In our case, the use of a prolonged course of anti-inflammatory medications (>3 months) resulted in symptom resolution and may potentially be an alternative therapy prior to surgical reconstruction. As pathogenesis of pain associated with congenitally absent pericardium is unclear, the mechanism behind this treatment modality remains uncertain. Efficacy of treatment with anti-inflammatory medications suggests that underlying inflammatory process may be part of pain generation, though interestingly, CRP and ESR were normal. This may aid future research in pathogenesis of pain in congenitally absent pericardium.

This patient's past medical history was significant for Swyer-James-MacLeod syndrome. However, in retrospect, this was an incorrect diagnosis and was due instead to cardiac levoposition.

Conclusion

In conclusion, a congenitally absent pericardium is a rare disorder, often undetected or misdiagnosed. There are characteristic findings on imaging such as a “Snoopy Sign” on a posterior-anterior chest X-ray, which can be easily missed because of its rarity. The goal of this report is to educate health care providers about this rare disorder.

Figure 4.

Cardiac CT shows absence of pericardium along the left ventricular free wall and leftward displacement of left ventricular apex (red arrow). There is the presence of pericardium along right atrium (yellow arrow).

Abbreviations

EKG

Electrocardiogram

CT

Computed tomography

MRI

Magnetic resonance imaging

HIV

Human immunodeficiency virus

ANA

Anti-nuclear antibody

ANCA

Anti-neutrophil cytoplasmic antibody

TSH

Thyroid stimulating hormone

CRP

C-reactive protein

ESR

Erythrocyte sedimentation rate

Conflict of Interest and Disclosure

This case report was approved by Institutional Review Board of Queens Medical Center for publication. Informed consent could not be obtained due to loss of follow up after resolution of symptoms. There is no identifiable data in this case report. All of authors do not have any disclosure or conflict of interest.