In two separate studies appearing in the August issue of the Journal of Bone and Joint Surgery, research teams led by Dr. Harry C. Dietz and Dr. Paul Sponseller of Johns Hopkins University in Baltimore, Md., suggest the checklist could help patients receive the monitoring and treatment necessary to prevent these genetic diseases from becoming life-threatening.
Marfan syndrome and Loeys-Dietz syndrome are both caused by mutations in specific genes. Both gene defects lead to visible bone abnormalities, as well as less visible but more serious cardiovascular problems such as aneurysms.
The severe complications of Loeys-Dietz syndrome can occur in young adulthood, making an appropriate diagnosis important so that monitoring and preventive treatment with drugs that lower blood pressure and even surgery can be administered in time.
"Patients may be diagnosed by their pediatrician, their family physician, their internist, eye doctors especially, and general orthopedic surgeons," Sponseller said in an interview.
Because many of the clinical features aren't pathologic by themselves -- such as long thumbs, narrow skulls, and flat feet -- it's important not to send too many patients for expensive genetic testing or cardiologic evaluations, he said.
Consequently, the researchers sought to develop relatively short lists of signs and symptoms, such as narrow skull, long thumbs, and flat feet, that would warrant referring patients to a specialist.
The combination of facial features and the "thumb sign" was both highly specific and sensitive for diagnosis in a study of 183 Marfan patients and 1,257 controls, Sponseller and colleagues reported.
They also noted two other features that were found in some Marfan patients but virtually never in healthy controls: a widening of the sac that surrounds the spinal cord and a defect of the hip socket.
Patients with Loeys-Dietz syndrome shared many of the skeletal features of Marfan syndrome, the researchers found. But they also had signs not seen in Marfan patients, such as widely spaced eyes, easily damaged skin and a cleft palate.
"The two syndromes have more differences than similarities," the researchers noted.
"The beauty of our lists is that they require no fancy imaging tests and most of the signs are right there for the pediatricians and the orthopedic surgeons to see," Sponseller said in a Hopkins press release.
Dr. Dianna Milewicz of the University of Texas Health Science Center in Houston said clinicians need to know how to recognize Loeys-Dietz as well as Marfan syndrome.
"It's important for us to identify who has these conditions because both of these syndromes can cause premature death if they go unrecognized," she said in an interview.
"These studies really highlight what specific outward manifestations will alert a physician that a patient has either Marfan syndrome or Loeys-Dietz syndrome."
Marfan syndrome has an estimated prevalence of one or two cases per 10,000 people. Loeys-Dietz syndrome was first recognized in 2005 as distinct from Marfan syndrome and its genetic basis confirmed in 2006. Its prevalence has not been firmly established.