0022-202X/82/79o:l-090s$02.00/0 THE .JOURNAL OF INVESTIGATIVE DERMATOLOGY, 79:908-92s, 1982 V "I. 7�). Supplement I Copyright © 1!J82 hy The Williams & Wilkins Co. Printed in U.S.A. Molecular Defects in the Ehlers-Danlos Syndrome SHELDON R. PINNELL, M.D. Division of Dermatology, Department of Medicine, Duke University Medical Center, Durham, North Carolina, U.S.A Several abnormalities in collagen biosynthesis have of lysyl hydroxylase. Two mutant enzymes have been charac­ been described in patients with Ehlers-Danlos syndrome. terized. One has an altered affInity for ascorbate and is ther­ Examples of collagen structural mutations as well as mally labile [5]. This apparently represents a structural muta­ post-translational enzymatic defects have been detected. tion of the enzyme. The other enzyme was kinetically normal Patients with hydroxylysine-deficient collagen disease but the activity was markedly diminished [6). This may repre­ (Ehlers-Danlos type VI) have diminished lysyl hydroxy­ sent a structural or regulatory mutation. lase activity. One mutant enzyme has been characterized The relative hydroxylation of tissue collagens has been vari­ which is thermally labile and had an altered affinity for able in this disorder [2, 7]. Although skin was markedly defIcient ascorbate. Another mutant enzyme had a normal re­ in hydroxylysine, bone was less defIcient and cartilage was quirement for cofactors but activity was diminished. normally hydroxylated. The explanation for this variability is Type VII Ehlers-Danlos syndrome is associated with unknown although enzymatic polymorphism has not been ex­ altered processing of procollagen to collagen. Most often cluded. Indeed evidence for isozymes has been reported [8]. the disorder is associated with deficient procollagen When cell lysates from a lysyl hydroxylase defIcient cell strain aminoprotease activity. One patient appears to repre­ were tested against substrates for types I and IV collagen, sent a structural mutation of pro 0'2 (I) resulting in in­ preferential activity was demonstrated against type IV collagen. complete cleavage of the amino terminal propeptide. One In one study an almost normal hydroxylysine content in skin family with x-linked Ehlers-Danlos syndrome (type V) collagen was described in association with lysyl hydroxylase has been described with altered lysyl oxidase activity. defIciency [9]. Subsequent analysis of these skin fIbroblasts Other patients with this disorder have had normal lysyl however has revealed normallysyl hydroxylase activity (Murad oxidase activity. The ecchymotic form of Ehlers-Danlos S, Pinnell SR: unpublished observations and Steinmann B: syndrome (type IV) has defective type III collagen syn­ personal communcation). thesis. Patients have been described with absent synthe­ The hydroxylysine content of complement component Clq sis, diminished synthesis and diminished secretion. was slightly low [10] or normal [ll] and functional activity was unimpaired. Therapy with large doses of ascorbate was effective in one The Ehlers-Danlos syndrome is a striking clinical syndrome patient with this disorder [12]. He was able to boost his urinary with rubber-like skin, hypermobile joints, a tendency to bruise excretion of hydroxylysine although hydroxyproline excretion easily, and poor wound healing [1). In general most forms of was coordinately increased. The effect appears to be due to an the disorder are compatible with normal longevity; a striking overall stimulation of collagen synthesis by ascorbate [1.3] exception is the ecchymotic form of Ehlers-Danlos syndrome rather than specific stimulation of lysyl hydroxylase activity. in which premature demise occurs regularly from arterial or Kinetic studies of his mutant enzyme failed to detect any intestinal rupture. In 1972, the fIrst human molecular disorder alteration in affinity for ascorbate [6). of collagen, hydroxylysine-defIcient collagen disease, was de­ Ehlers-Danlos 2 scribed in 2 sisters with syndrome [ ). Since then TYPE VII EHLERS-DANLOS SYNDROME: several ultrastructural and biochemical collagen defects have ARTHROCHALASIS MULTIPLEX CONGENITA been described in the Ehlers-Danlos syndrome (Table). This manuscript will focus on 4 types of Ehlers-Danlos syndrome in In 1973, Lichtenstein et al reported studies on :1 type VII which biochemical collagen defects are best understood: types Ehlers-Danlos patients with a defect in conversion of procolla­ VI, VII, V, and IV. The range of defects is representative of the gen to collagen [14]. These patients had short stature, hyper­ complex nature of collagen biosynthesis. These appear to in­ extensible joints, and bilateral hip dislocation. Analysis of col­ clude structural and regulatory collagen genomic alterations as lagen extracted from their skin revealed elongated oc] (I) and well as intracellular and extracellular post-translation enzy­ OC2 (I) chains resulting from inefficient conversion of type I matic defects. procollagen. Their cultured skin fibroblasts had deficient pro­ collagen aminoprotease activity. Uncleaved aminoterminal pro­ TYPE VI EHLERS-DANLOS SYNDROME: peptides apparently interfere with fibrillogenesis and intermo­ HYDROXYLYSINE-DEFICIENT COLLAGEN DISEASE lecular crosslinking resulting in the fragile connective tissue. This disorder, inherited as an autosomal recessive, is bio­ In 1972, Pinnell et al described 2 sisters with type VI Ehlers­ chemically similar to dermatosparaxis found in sheep [15] and Danlos syndrome who had marked hyperextensibility of skin cattle [16]. The striking skin fragility characteristic of derma­ and joints, severe scoliosis, and marfanoid features [2). Levels tosparaxis however, is absent in the Ehlers-Danlos patients. of hydroxylysine in skin collagen were found to be less than one The reason for this difference is not understood. per molecule of collagen and levels of hydroxylysine-derived Recently another patient with type VII Ehlers-Danlos syn­ cross-links were marked diminished [3]. The disorder is due to drome has been described with inefficient conversion of procol­ deficient lysyl hydroxylase activity [4] and is inherited as an lagen to collagen [17]. This patient has normal levels of procol­ autosomal recessive. Heterozygotes have intermediate activities lagen aminoprotease. Conversion of pro collagen appears to be impeded by a structural mutation in her pro OC2 (1) near the This work was supported by grant 5 R01 AM-17128 from the protease cleavage site. Pro oc] (I) is normally converted but the National Institutes of Health. aminopropeptide of pro OC2 (I) remains uncleaved apparently This is publication number 121 from the Dermatological Research resulting in similar difficulties in fibrillogenesis found in other Laboratories of Duke University Medical Center. Reprint requests to: Sheldon R. R. Pinnell, M.D., Division of Der­ patients with this form of Ehlers-Danlos syndrome. This patient matology, Department of Medicine, Duke University Medical Center, has, in addition to an abnormal pro OC2 (I), an equal complement Durham, NC 27710. of normal pro (\'2 (I). She apparently represents a new structural 90s July 1982 EHLERS-DANLOS SYNDROME 918 Ultrastructural and biochemical collagen defects in Ehlers-Danlos Danlos syndrome with absent type III collagen synthesis [23]. syndrome Skin, aorta, gut, bone, and tendon were obtained shortly after Major clinical Ultrastructural Biochemical de- death. Cyanogen bromide cleavage of these tissues revealed Type features defect feet absence of peptides characteristic of type III collagen. Skin I (Gravis) Marked joint and Variable collagen Unknown fibroblasts in culture failed to synthesize any detectable type skin hyperexten- fibril diameter III procollagen. In addition, characteristic cellular staining was sibility. Fragile [29-31] skin, poor absent in cultured skin fibroblasts from the patient using anti­ wound healing sera specific for type III collagen and procollagen [24]. This and easy bruisa - patient may have had a gene deletion for type III procollagen. bility. Subsequent studies of fibroblasts from patients with type IV II (Mitis) Small joint hyper- Variable collagen Unknown mobility fibril diameter Ehlers-Danlos syndrome have revealed diminished but not [30,31] absent levels of type III collagen synthesis [25, 26]. They may III (Benign hy- Large joint hyper- Small collagen fi- Unknown represent structural or regulatory mutations. Electron micro­ perrnobile) mobility bril diameter scopic studies have revealed small collagen fiberdiametrers [26, [30] IV (Ecchy- Marked bruisabil- Small collagen fi- Diminished 27]. In 2 patients distended endoplasmic reticulum has been motic) ity. arterial and bril diameter [25-28] or ab- demonstrated in skin [28] and lung [26] fibroblasts. These intestinal rup- [27] sent [23] type fibroblasts demonstrated diminished total collagen synthesis ture Dilated endoplas- III collagen syn- and markedly deficient type III collagen synthesis [26, 28]. mic reticulum thesis. Some pa- [26,27] tients may have They may represent mutations which interfere with cellular secretion defect secretion. [26,27] The Ehlers-Danlos phenotype is obviously associated with V (X-linked) Moderate joint hy· Variable collagen Some patients defective collagen structure. The variety of structural defects permobility. fibril diameter may have lysyl and abnormalities in post-translational modifications repre­ Heart valve pro- [30,31] oxidase defi- lapse. ciency [17J sented by the different forms of Ehlers-Danlos syndrome are VI (Hydroxy- Marked