Tuesday, January 23, 2007

Marfan Syndrome

Marfan syndrome:

The frontal and lateral radiographs (see Images 1-2) demonstrate scoliosis of the thoracic spine and evidence of previous orthopedic repair. The thorax is elongated in the craniocaudal dimension, and the lateral radiograph additionally demonstrates a striking pectus carinatum, or pigeon chest, a deformity in which the sternum is protruded in a convex shape. Taken together, the skeletal abnormalities suggest Marfan syndrome. This connective tissue disorder primarily affects the skeleton, the cardiovascular system, and the eye and occurs in 1-2 per 10,000 persons. Marfan syndrome is a primarily inherited genetic defect with autosomal dominant transmission, though approximately 30% of all cases result from spontaneous mutations.

Classic Marfan syndrome results from mutations in the
FBN1 locus on the fibrillin gene on chromosome 15. The skeletal manifestations of Marfan syndrome can vary. Individuals with Marfan syndrome are characteristically tall and thin, with limbs that are disproportionately long in relation to their trunk (dolichostenomelia). The patient's arm span can be greater than his or her height. Arachnodactyly is a classic finding on physical examination and is defined as long fingers and toes and chest deformities. Such deformities often include pectus carinatum, or pectus excavatum, which is funnel chest characterized by concave depression of the sternum. Ligamentous laxity may result in pes planus and angular deformities of the joints. Scoliosis, or lateral curvature of the spine, may be present as a result of the same mechanisms that produce the pectus deformity.

Ocular abnormalities include ectopia lentis and a displaced or malpositioned lens. The most common ocular findings in Marfan syndrome are superior or lateral dislocation, myopia, retinal detachment, and cataracts. Cardiovascular manifestations are due to cystic medial necrosis, which can result in catastrophic aneurysm and/or dissection of the aortic and pulmonary arteries. Insufficiency of the aortic valve can result from aortic dilation. Mitral valve disease with prolapse is also encountered.

In 1990, Flanagan et al first described the association of iliac artery aneurysm with Marfan syndrome. They postulated that the weakness of the arterial tree caused by cystic medial necrosis is more widespread than initially appreciated. Savolainen et al (1993) later supported this hypothesis.

In the current patient, thrombus is present in an aneurysm of the left common iliac artery. It measures a maximum of 2.8 cm, as identified on the contrast-enhanced CT scan of the abdomen and pelvis (see Image 3). As a result of the extensive thrombus in the aneurysm, the patient underwent open repair rather than endoluminal graft placement. At the time of this report, no complications occurred.

Of interest, CT scanning also revealed enlargement of the dorsal aspect of the thecal sac (see Image 4) in the lumbosacral region of the spine. Another major diagnostic criterion of Marfan syndrome is a dilated, CSF-filled area known as lumbosacral dural ectasia.
Pectus deformities of the chest occur in approximately 1 of 1000 of the general population, they are more frequent in men than in women, and they vary in severity. The cause of these disorders is thought to be
excessive growth of the costal cartilages that results in inward or outward buckling of the sternum. This buckling is often noticeable at birth, but the characteristic chest deformity manifests as the patient enters adolescence. Many patients have additional asymmetry and rotational deformity of the chest and sternum, which may lead to scoliosis. Two conditions associated with pectus deformities are Marfan syndrome, as in this case, and Poland syndrome.

For more information regarding the genetics of Marfan syndrome, including a full discussion of the major and minor diagnostic criteria, see the eMedicine article
Marfan Syndrome (within the Orthopedic Surgery specialty).

  • Resnick D, Kransdorf MJ. Bone and Joint Imaging. 3rd ed. Philadelphia, Pa: Elsevier Saunders, 2005:1279-80.
  • Flanagan PV, Geoghegan J, Egan TJ. Iliac artery aneurysm in Marfan's syndrome. Eur J Vasc Surg 1990 Jun;4(3):323-4.
  • Savolainen H, Savola J, Savolainen A. Aneurysm of the iliac artery in Marfan's syndrome. Ann Chir Gynaecol 1993;82(3):203-5.
  • Channell K, Washington ER. eMedicine Journal [serial online]. 2004. Available at: http://www.emedicine.com/orthoped/topic414.htm.
BACKGROUND of this case:

A 51-year-old man presents to the vascular surgery clinic for repair of an iliac artery aneurysm that was incidentally discovered on abdominal and pelvic CT (image to follow). The patient did not have previous trauma that required surgical intervention. Review of the rest of his medical history is temporarily postponed.

On physical examination, the patient's vital signs are normal. In terms of general appearance, the patient is a well-developed, well-nourished, tall, and thin man. Respiratory examination yields normal findings, but the chest examination reveals a tall, narrow thorax with outward protrusion of the chest wall. Abdominal findings are normal. Musculoskeletal examination reveals long, thin fingers and toes. The patient has good (2+) pulses in the bilateral dorsalis pedis and posterior tibial arteries. Chest radiography is performed as part of the routine preoperative evaluation (see Images 1-2).

Author: Adam W. Chandler, MD,
University of New Mexico Hospital Residency,
Department of Radiology, Albuquerque

Gautam Dehadrai, MD,
Department of Radiology,
Norman Regional Hospital,
Norman, Okla

eMedicine Editor: Rick G. Kulkarni, MD,
Assistant Professor,
Yale School of Medicine,
Section of Emergency Medicine,
Department of Surgery,
Attending Physician,
Medical Director,
Department of Emergency Services,
Yale-New Haven Hospital, Conn
Source: eMedicine.com - http://master.emedicine.com/email/radio/radio120/radio120answer.html


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