Day: January 11, 2015

January 11, 2015

Abstract

Background

Ehlers-Danlos syndrome type IV, the vascular type, results from mutations in the gene for type III procollagen (COL3A1). Affected patients are at risk for arterial, bowel, and uterine rupture, but the timing of these events, their frequency, and the course of the disease are not well documented.

Methods

We reviewed the clinical and family histories of and medical and surgical complications in 220 index patients with biochemically confirmed Ehlers-Danlos syndrome type IV and 199 of their affected relatives. We identified the underlying COL3A1 mutation in 135 index patients.

Results

Complications were rare in childhood; 25 percent of the index patients had a first complication by the age of 20 years, and more than 80 percent had had at least one complication by the age of 40. The calculated median survival of the entire cohort was 48 years. Most deaths resulted from arterial rupture. Bowel rupture, which often involved the sigmoid colon, accounted for about a quarter of complications but rarely led to death. Complications of pregnancy led to death in 12 of the 81 women who became pregnant. The types of complications were not associated with specific mutations in COL3A1.

Conclusions

Although most affected patients survive the first and second major complications, Ehlers-Danlos syndrome type IV results in premature death. The diagnosis should be considered in young people who come to medical attention because of uterine rupture during pregnancy or arterial or visceral rupture. (N Engl J Med 2000;342:673-80.)

The clinical diagnosis of Ehlers-Danlos syndrome type IV, the vascular type, is made on the basis of four clinical criteria: easy bruising, thin skin with visible veins, characteristic facial features, and rupture of arteries, uterus, or intestines. The diagnosis is confirmed by the demonstration that cultured fibroblasts synthesize abnormal type III procollagen molecules or by the identification of a mutation in the gene for type III procollagen (COL3A1). Hypermobility of large joints and hyperextensibility of the skin, characteristic of the more common forms of Ehlers-Danlos syndrome, are unusual in the vascular type. Ehlers-Danlos syndrome type IV, an autosomal dominant disorder, is uncommon (the precise incidence and prevalence are not known), and in part because of its rarity, the diagnosis is often made only after a catastrophic complication or at postmortem examination. As is often the case with rare genetic disorders, physicians’ unfamiliarity with the condition may compromise care. Although there are many brief clinical descriptions and case reports focusing on the molecular genetics, the scope of the clinical complications, the results of therapeutic intervention, and information about survival are not readily available. To provide the basis for a better understanding of the course of the disorder and for more informed counseling of patients and their families, we studied the clinical records of 220 index patients, in whom the diagnosis was confirmed by biochemical analysis, and 199 of their affected relatives.

Methods

Study Subjects

The 220 index patients included all 217 patients whose cultured fibroblasts synthesized abnormal type III procollagen molecules who were evaluated in Seattle between 1976 and 1998 and 3 additional patients who were evaluated biochemically in Zurich, Switzerland, before 1990. We personally examined members of 13 families in Seattle and 3 families in Zurich. From the medical records of each index patient we determined the reasons for the initial referral to a physician and assessed the medical history, family history, physical findings, and when included, autopsy results.
We used three criteria to designate 199 relatives of the index patients as having Ehlers-Danlos syndrome type IV: cultures of dermal fibroblasts synthesized abnormal type III procollagen molecules in the case of 44 relatives; a familial molecular genetic abnormality was identified in the DNA of 35 relatives; and evidence in the family-history portion of the index patient’s records indicated that the relative had had an arterial rupture, dissection, or aneurysm, bowel perforation, or organ rupture in the case of 120 relatives. Additional clinical data were provided for the first two groups of relatives at the time of testing; only data in the medical records of the index patient were available in the case of the remaining relatives.

Relatives were classified as unaffected if they were reported by a physician to be unaffected, if the results of biochemical or molecular genetic studies excluded the diagnosis, or if they had not had a major complication by the age of 50 years. We identified 462 relatives with a 50 percent risk of inheriting the condition on the basis of family-history data, of whom 238 (51.5 percent) were affected. Forty of the 224 apparently unaffected relatives were younger than 16 years of age and had not been tested, so their status could not be confirmed. These data suggest that most affected members of these families were identified.

From available medical records of the index patients and some of their relatives, we determined the number and type of medical or surgical complications, the ages at which they occurred, the cause of and age at death, reported birth defects, and identified complications of pregnancy. The age at testing (i.e., ascertainment) in the index patients was the age at which we confirmed the diagnosis. For their affected relatives, the age at ascertainment was the age at which we identified them with the use of biochemical or molecular genetic studies, their last known age, or their age at death, as recorded in the family history. The age at ascertainment was known for 374 of the 419 subjects (207 index patients and 167 relatives) and ranged from 1 to 78 years. The index patients were identified at a younger age than were their affected relatives, as would be expected when family histories are used to identify affected members of prior generations. Except for the study subjects who lived in our local communities, we did not follow most subjects after the diagnosis of Ehlers-Danlos syndrome type IV.

Seventy percent of the index patients (154 of 220) were referred for evaluation after a major event. Sixty-six index patients who had had no complications had one or more physical findings consistent with the diagnosis (characteristic facial features, thin skin with visible veins, easy bruising, and increased joint mobility of the hands) that led to the evaluation. Thirty-two of these 66 patients also had affected relatives who had had complications.

Biochemical and Molecular Studies

Dermal fibroblasts were obtained from the subjects and cultured, and the synthesis of type III procollagen was studied as described previously. For the molecular studies, RNA and DNA were extracted from cultured fibroblasts, and complementary DNA was synthesized by reverse transcription from RNA. Overlapping fragments of complementary DNA were amplified by the polymerase chain reaction and analyzed by electrophoresis on polyacrylamide gels to identify insertions or deletions or by single-strand conformation polymorphism analysis to detect point mutations in the coding sequence. Abnormal fragments were sequenced by the dideoxy chain-termination method with T4 polymerase (Sequenase, U.S. Biochemicals, or Prism model 310 genetic analyzer, Applied Biosystems). All mutations were confirmed by sequence analysis or restriction-enzyme digestion of genomic DNA.

Statistical Analysis

We used a two-sample t-test, assuming that variance was unequal, to compare the mean age at ascertainment and at the time of complications in the index patients and their affected relatives. We used life-table methods to estimate survival (SPSS statistical software, version 7.5) and included the age at death (including information on two index patients whose deaths were apparently unrelated to any complication of Ehlers-Danlos syndrome type IV) or the last known age of each living subject. We constructed a normal curve from the 1994 age-specific death rates from the Division of Vital Statistics of the Centers for Disease Control and Prevention. We compared Kaplan-Meier survival curves for the index patients and their relatives using a log-rank statistical analysis (SPSS software, version 7.5). We also used Kaplan-Meier analysis to calculate survival free of a first complication for the index patients (SPSS software, version 7.5) by plotting the expression [1-(cumulative survival)] against age, with survival defined according to the age at the time of the first complication.

We computed standardized incidence ratios to compare the rate of birth defects in our affected subjects with the rate in the general population. The ratios and 95 percent confidence intervals were calculated on the assumption that the values followed a Poisson distribution. All P values were two-sided.

Results

Survival

A total of 131 subjects died: 26 index patients and 105 relatives. The overrepresentation of relatives probably reflects our method of ascertaining their disease status by using the records of younger index patients and the clinical criteria for diagnosis and inclusion. The median survival for the entire cohort was 48 years. The age at death ranged from 6 to 73 years. The median survival of the index patients was longer than that of their affected relatives. It is not clear whether this difference reflects the different age distributions in the two groups or recent improvements in medical care.

Causes of Death

Most deaths resulted from arterial dissection or rupture. Of 103 deaths caused by arterial rupture, 78 involved thoracic or abdominal vessels and 9 resulted  

The classical features of Ehlers-Danlos Syndrome type III (EDS) are hyperextensibility of the joints, hyperelasticity and fragility of the skin. Only minor visible changes of the skin and joint hypermobility makes this syndrome difficult to distinguish from the more common simple hypermobility. Ehlers-Danlos syndrome is claimed to be a rare syndrome with an incidence of 1/150,000. Since we initiated our research on this syndrome, we have found 4 families in an area with about 300,000 inhabitants. The syndrome, therefore, seems to be more common than assumed and the reason why the syndrome is not diagnosed can be due to the fact that the syndrome is diagnosed as hypermobility.

 We have observed that local anesthesia has an insufficient effect in Ehlers-Danlos type III patients and that it is difficult to distinguish the Ehlers-Danlos type III syndrome from hypermobile patients diagnostically. In genetic advising and prognosis of the EDS patients, there is a need for new tools to separate them from hypermobile patients. We, therefore, investigated quantitatively if the Ehlers-Danlos type III patients objectively responded differently from hypermobile patients to cutaneous analgesia, and we sought to find out if these parameters could be used as a new test to discriminate between the two diseases.

Topical analgesics (EMLA cream) was applied to seven EDS patients, ten hypermobile patients, and to fifteen controls. The depth of the cutaneous analgesia was measured by sensory and pain threshold depths to controlled needle insertions. It should be easy to carry out the measurements in the daily clinical situation. EMLA cream is commonly available and insertion of the needle can be done without the special equipment used in this study. Controls and hypermobiles did not differ in their response to cutaneous analgesia. The thresholds to cutaneous laser simulation and the depth of analgesia increased significantly less in the Ehlers-Danlos patients, compared to the two other groups. In clinical practice, a needle insertion test can easily be applied to investigate if patients are responders or non-responders to local analgesics.

 When the Ehlers-Danlos type III patients were biopsied in the hip region for skin biopsy, they all reported considerable pain although large doses (5 ml) of 1% lidocaine-epinephrine were infiltrated subcutaneously. When we asked them for more details, they reported that they had all previously experienced difficulties in obtaining a sufficient analgesia at the dentist, although they had been given substantial doses of local analgesics. Some of the women reported no pain alleviation of local analgesics when they were sutured after episiotomy. They were commonly characterized as hysterics. We have definitely proved that this is not the case.