Ehlers-Danlos Syndrome, Kyphoscoliotic Type, 1

A number sign (#) is used with this entry because Ehlers-Danlos syndrome kyphoscoliotic type 1 (EDSKSCL1), previously designated EDS6, is caused by homozygous or compound heterozygous mutation in the gene encoding lysyl hydroxylase (PLOD1; 153454) on chromosome 1p36.

Description

The Ehlers-Danlos syndromes (EDS) are a group of heritable connective tissue disorders that share the common features of skin hyperextensibility, articular hypermobility, and tissue fragility. The major characteristics of kyphoscoliotic-type EDS are severe muscle hypotonia at birth, generalized joint laxity, scoliosis at birth, and scleral fragility and rupture of the ocular globe (Beighton et al., 1998).

Nevo syndrome, previously thought to be a distinct entity, is identical to EDS type VI (Voermans et al., 2009).

Genetic Heterogeneity of Ehlers-Danlos Syndrome, Kyphoscoliotic Type

See EDSSKCL2 (614557), caused by mutation in the FKBP14 gene (614505).

Classification of Ehlers-Danlos Syndromes

The current classification of Ehlers-Danlos syndromes is based on a 2017 international classification described by Malfait et al. (2017), which recognizes 13 EDS subtypes. This classification revised the 'Villefranche classification' reported by Beighton et al. (1998).

Beighton et al. (1998) reported on a revised nosology of the Ehlers-Danlos syndromes, designated the Villefranche classification. Major and minor diagnostic criteria were defined for each type and complemented whenever possible with laboratory findings. Six main descriptive types were substituted for earlier types numbered with Roman numerals: classic type (EDS I and II), hypermobility type (EDS III), vascular type (EDS IV), kyphoscoliosis type (EDS VI), arthrochalasia type (EDS VIIA and VIIB), and dermatosparaxis type (EDS VIIC). Six other forms were listed, including a category of 'unspecified forms.'

Clinical Features

In 2 sisters with features somewhat suggestive of the Ehlers-Danlos syndrome, Pinnell et al. (1972) found deficiency of hydroxylysine in collagen with stoichiometric replacement by lysine, and Krane et al. (1972) found deficiency of collagen lysyl hydroxylase. Hydroxylysine is important to cross-linking of collagen. Skin collagen was abnormally soluble. Clinical features included severe scoliosis from an early age, recurrent joint dislocations, stretchable skin, premature rupture of fetal membranes, and floppiness in early life, leading to the diagnosis of amyotonia congenita in one. The same patient, aged 9 years, had had one eye enucleated after an automobile accident.

McKusick (1966) had a patient who appeared to have the same defect; the distinctive clinical features suggested the mnemonic designation ocular-scoliotic form of EDS. This patient was reported earlier in the ophthalmologic literature (Durham, 1953), and was later studied enzymatically by Sussman et al. (1974). On the basis of this patient, Beighton (1970) raised the possibility of an autosomal recessive form of the Ehlers-Danlos syndrome in which skin and joint changes like those of the dominant form occur but in which serious ocular complications, particularly retinal detachment, are a conspicuous feature. He described an affected brother and normal parents. The brother had 4 unaffected children. The affected female died at the age of 50 years with symptoms typical of acute dissecting aneurysm of the aorta (autopsy was not performed).

Studying collagen in a clinically unspecified case of Ehlers-Danlos syndrome, Mechanic (1972) found a deficiency of hydroxylysinonorleucine and other crosslinks and suggested a cross-linkage defect in this disease.

The patient studied by Miller et al. (1978) had microcornea but no scoliosis. Vitamin C, 4 g per day (plasma level 0.5-2.0 microg/dL), increased muscle strength, corneal size, and rate of wound healing. Elsas et al. (1978) described a patient with apparent benefit from ascorbic acid.

Krieg et al. (1979) studied the affected son of third-cousin parents, both of whom had half-normal amounts of hydroxylysine in dermal collagen. The fetal membrane broke 34 hours before birth. He was limp with flexible kyphosis, very loose joints, and hematomas of the conjunctivae, eyelids, and ears. The diagnosis of EDS and studies of skin biopsy material were made when he was 3 months old.

Farag and Schimke (1989) described an Arab brother and sister with the phenotype of EDS VI who also had peripheral polyneuropathy. Both had aortic regurgitation and mitral valve prolapse. The parents were consanguineous. Although Farag and Schimke (1989) suggested that this might be a new form of the Ehlers-Danlos syndrome, they recognized the obvious possibility that these were 2 independent recessive traits in this inbred kindred.

Wenstrup et al. (1989) reviewed the clinical features of 10 patients with lysyl hydroxylase deficiency. The distinctive feature common to all was muscle hypotonia with joint laxity in the newborn period and moderate to severe kyphoscoliosis. They concluded that these patients are at risk for catastrophic arterial rupture. One patient had an intracranial hemorrhage in the perinatal period without evident traumatic delivery or ventilator-dependent respiratory distress syndrome. Another patient had a rupture of a vertebral artery, and 1 had multiple ruptures of the femoral artery and 2 episodes of spontaneous intrathoracic arterial rupture. Remarkably, ocular features were relatively insignificant in the 10 patients reviewed by Wenstrup et al. (1989). One patient was said to have no abnormality, not even myopia; 2 patients had severe myopia, and 7 others had mild to moderate myopia. Three patients, including the 2 patients with severe myopia had corneal diameters measured; all were mildly decreased. One patient had bilateral glaucoma; another had unilateral retinal detachment.

Yeowell and Walker (1997) reported a male patient with EDS VI who was born in 1989 to healthy nonconsanguineous parents and was delivered at 38 weeks by cesarean section after a failed eversion to correct the breech position and with known oligohydramnios. He was hypotonic at birth, with multiple contractures of the arms and legs that were considered to be positional. Although he was alert and socially interactive, his general and gross motor development progressed slowly. Kyphoscoliosis was noted early and progressed rapidly. At 9 months, an L5-S1-level spina bifida occulta was identified together with progressive leftward thoracic kyphoscoliosis. Bilateral inguinal hernias were repaired at 3 months; congenital esotropia was corrected at 7 months of age. Since infancy he was observed to have extreme joint hypermobility, soft velvety skin, easy bruisability, and the tendency to develop keloids in response to minor trauma. A highly arched palate was noted as well as increased vertex height of the skull without abnormality of the sutural plates. His academic and personal-social skills were precocious.

Heim et al. (1998) described an Iranian patient, the son of consanguineous parents, who developed kyphoscoliosis at the age of approximately 3 years and glaucoma at the age of 10 years. At the age of 13 years he had a marfanoid habitus. He was able to walk only with the upper part of his body bent forward and preferred sitting in a wheelchair. He had microcornea, myopia, brownish sclerae, and tortuous retinal arteries.

Salavoura et al. (2006) reported a 4-year-old girl with EDS VI. At birth, she showed neonatal hypotonia, torticollis, dislocation of the shoulders and hips, joint laxity, scoliosis, and talipes equinovarus. At age 4 years, she had severe scoliosis, clumsy and unsteady gait, heart murmur, and thin, hyperelastic skin with easy bruisability. Ocular examination was normal. Biochemical analysis showed an increased urinary lysyl pyridoline/hydroxylysyl ratio. Treatment with high doses of ascorbic acid resulted in improved healing and muscle strength.

Nevo et al. (1974) described an inbred Israeli family in which 2 sibs and their cousin had increased growth, kyphosis, prominent forehead, volar edema, spindle-shaped fingers, wrist drop, talipes, hyperbilirubinemia, and generalized hypotonia. Although the authors considered their cases to be an autosomal recessive variant of Sotos syndrome (117550), Cohen (1989) proposed that these patients had a separate entity, which they called the Nevo syndrome. A similar case was reported by Hilderink and Brunner (1995). Their patient, a boy born to consanguineous parents, had neither lens luxation nor aortic dilatation.

Al-Gazali et al. (1997) described 2 male patients from unrelated Arab families with features similar to those described by Nevo et al. (1974) but without hyperbilirubinemia. Both had delayed motor development. Cognitive function was normal in one at 2 years 10 months of age. While the other was too young to assess, social responses appeared normal. MRI studies in the older child revealed extreme hyperlordosis of the cervical spine and a wide spinal canal suggestive of dural ectasia.

Because the clinical features in patients reported with Nevo syndrome were similar to those of EDS VIA, Giunta et al. (2005) studied 7 patients diagnosed with Nevo syndrome, 2 of whom had been reported by Al-Gazali et al. (1997) and 1 by Hilderink and Brunner (1995), and identified homozygous mutations in the PLOD1 gene in all (see 153454.0001 and 153454.0006). In the 5 patients from whom urine was available, the ratio of total urinary lysyl pyridinoline to hydroxylysyl pyridinoline was elevated compared with that in controls and similar to that observed in patients with EDS VIA. Giunta et al. (2005) concluded that Nevo syndrome is allelic to and clinically indistinguishable from EDS VIA and presented evidence that increased length at birth and wrist drop, in addition to muscular hypotonia and kyphoscoliosis, should prompt the physician to consider EDS VIA earlier than had previously been the case.

Voermans et al. (2009) reexamined a male patient, born of first-cousin parents from the Netherlands, who was originally reported by Hilderink and Brunner (1995) and in whom Giunta et al. (2005) identified homozygosity for a deletion in the PLOD1 gene (153454.0006). At the age of 16 years, generalized muscle weakness and mild muscle hypotonia were still present, and the patient had reduced muscle mass. Deep tendon reflexes were symmetrically depressed, vibration sense was reduced in hands and feet bilaterally, and tandem gait was mildly impaired, but position sense of fingers and toes and coordination tests of arms was normal. In addition, he had hyperextensible skin with atrophic scars, contracture of the right elbow, and hypermobility of distal joints. Nerve conduction studies were compatible with a mild sensorimotor axonal polyneuropathy, and electromyography reflected a myopathy. MRI revealed myopathic changes in increase of fat tissue and atrophy of muscles. Needle biopsy of the right quadriceps muscle at 16 years of age showed fibrous and fatty tissue with very few remaining muscle fibers, in contrast to an earlier biopsy at 2 months of age which showed no abnormalities. Voermans et al. (2009) suggested that myopathy or peripheral nerve dysfunction might contribute to the functional decline in adolescence that is observed in patients with EDS VIA, with loss of ambulation in the second or third decade.

Diagnosis

Traditionally, the clinical diagnosis of EDS VI is confirmed by an insufficiency of hydroxylysine on analysis of hydrolyzed dermis and/or reduced enzyme activity in cultured skin fibroblasts (for review, see Steinmann et al., 1993) but can also be confirmed by the altered urinary ratio of lysyl pyridinoline:hydroxylysyl pyridinoline which is characteristic for EDS VI (Steinmann et al., 1995).

Dembure et al. (1984) demonstrated the feasibility of prenatal diagnosis and carrier detection.

Molecular Genetics

In cells from 2 sisters with type VI Ehlers-Danlos syndrome in whom Pinnell et al. (1972) first demonstrated reduced lysyl hydroxylase activity, Hautala et al. (1993) demonstrated homozygosity for a large duplication in the PLOD1 gene, corresponding to 7 exons (153454.0002), caused by an Alu-Alu recombination. The same mutation was found by Pousi et al. (1994) in the patient reported by McKusick (1966) and Sussman et al. (1974).

Giunta et al. (2005) studied 7 patients diagnosed with Nevo syndrome, 2 of whom had been reported by Hilderink and Brunner (1995) and 1 by Al-Gazali et al. (1997), and found homozygous mutations in the PLOD1 gene in all (see 153454.0001 and 153454.0006).

In a child with EDS VI, Salavoura et al. (2006) identified a homozygous deletion in the PLOD1 gene.

Nomenclature

The kyphoscoliotic type of Ehlers-Danlos syndrome was at one time separated into EDS VIA (with lysyl hydroxylase deficiency) and EDS VIB (with normal lysyl hydroxylase activity). The designation EDS VIB was also thought to include the brittle cornea syndrome (229200), which was subsequently found to be a distinct disorder caused by mutation in the ZNF469 gene (612078). EDS VIB is now known as the musculocontractural type of EDS (601776), caused by mutation in the CHST14 gene (608429).

History

Ihme et al. (1983) described 3 variants of EDS VI: a severe form with skeletal, dermal and ocular manifestations with no hydroxylysine in skin collagen and low lysyl hydroxylase activity in cultured fibroblasts; a clinically similar form with nearly normal hydroxylysine content of skin but low enzyme activity in cultured fibroblasts; and a predominantly ocular form with no biochemical abnormality of skin or cultured fibroblasts.

Sigurdson et al. (1985) reported as a case of type IV EDS a 33-year-old man with colonic perforation. He 'was born with multiple congenital defects, including severe kyphoscoliosis, keratoconus, micrognathia, mild mental retardation, and joint laxity.' He had had bilateral inguinal herniorrhaphies and a corneal transplant for keratoconus. Colonoscopy showed wide-mouthed diverticula throughout the entire transverse and descending colon. Might this be the ocular-scoliotic form of EDS VI, rather than type IV?

Dumic et al. (1998) reported a patient with Nevo syndrome who manifested intrauterine and postpartum overgrowth, accelerated osseous maturation, dolichocephaly, highly arched palate, large and low-set ears, cryptorchidism, delayed neuropsychologic development, hypotonia, edema and contractures of the hands and feet, a single transverse palmar crease, and tapering digits. After meningococcal sepsis at age 6 months, he remained decerebrate. Thereafter, overgrowth and especially weight gain were markedly accelerated until his death at age 18 months, at which time his height was 103 cm and his weight was 23 kg. In addition to low plasma concentrations of growth hormone and insulin-like growth factor, severe insulin resistance was observed. Dumic et al. (1998) presumed that a selective defect in insulin-stimulated glucose uptake, with preservation of anabolic effect, was one of the causes of his 'overgrowth without growth hormone,' at least in the last 12 months of life after severe brain damage.