eMedicine Specialties > Neurology > Neuromuscular Diseases

Schwartz-Jampel Syndrome

Author: Stephen A Berman, MD, PhD, Professor, Department of Internal Medicine, Section of Neurology, Dartmouth Medical School; Chief, Neurology Service, White River Junction Veterans Medical Center
Coauthor(s): Eric Dinnerstein, MD, Consulting Staff Neurologist, Maine Neurology
Contributor Information and Disclosures

Updated: Feb 2, 2007

Introduction

Background

Schwartz-Jampel syndrome (SJS) is a term now applied to 2 different autosomal recessive inherited conditions, sometimes termed SJS type I and SJS type II. Both are very rare. SJS type I has 2 recognized subtypes, IA and IB, which are similar except that type IB manifests earlier and with greater severity. The most commonly recognized and described type is IA, which exhibits muscle stiffness, mild (and largely nonprogressive) muscle weakness, and a number of minor morphological abnormalities. In affected patients, problems with motor development frequently become evident during the first year of life. Usually, the characteristic dysmorphic features lead to an early diagnosis, no later than age 3 years. Types IB and type II (now known to be a separate disease more commonly referred to as Stuve-Wiedemann syndrome) are discussed in further detail later.

The first described cases of SJS were reported in 1962 by Oscar Schwartz and Robert S. Jampel in the Archives of Ophthalmology in an article titled "Congenital blepharophimosis associated with a unique generalized myopathy." In this paper, the authors present the case of 2 siblings, a 6-year-old boy and a 3-and-a-half-year-old girl, who had the following clinical characteristics:

• Congenital blepharophimosis (ie, decreased palpebral fissure with normal eyelid development)
• Unusual facies characterized by a puckered facial appearance
• Small muscle mass and joint deformities (eg, coxa valga, irregularity of the capital femoral epiphyses, pectus carinatum ["pigeon breast"])
• Hypertrichosis of the eyelids
• Slightly elevated serum aldolase level

Electromyography (EMG) was not performed. The authors opined that the disease might represent a generalized problem with muscle and tendon development during infancy.

As mentioned above, certain subtypes of SJS are now recognized. Type IA is the classic type described by Schwartz and Jampel. Types IB and a type II have also been delineated. Type IA becomes apparent later in childhood and is less severe. Type IB is apparent immediately at birth and is more severe clinically, although typically compatible with life and even long-term survival. Types IA and IB derive from mutations of the same gene, the HSPG2 gene, which codes for perlecan, a heparin sulfate proteoglycan.

Type II, like type IB, is apparent immediately at birth. The patients look similar to those with type IB. However, it was known for many years that type II does not map to the same chromosome as types IA and IB. It is now known that type II relates to a mutation in a different gene, the gene for the leukemia inhibitory factor receptor (LIFR). This is the same disease as Stuve-Wiedemann syndrome, which has been known separately, mainly in the rheumatologic and orthopedic literature, rather than the neurologic literature.

The cardinal features of type II are joint contractures, bone dysplasia, and small stature. Infants with type II have severe respiratory difficulties and feeding problems. Hypotonia (rather than stiffness) is prominent. Frequent bouts of hyperthermia have been described (possibly related to mitochondrial dysfunction). A high infant mortality rate is associated with this condition. Long-term survivors are rare. However, 2 long-term survivors, ages 3 and 12 years, have recently been reported (Di Rocco, 2003). In addition to problems with bone dysplasia, these children also manifested dysautonomic and neuropathic features, including reduced patellar reflexes, lack of corneal reflexes, and paradoxical perspiration at low temperatures. Their tongues lacked fungiform papillae (in addition to showing ulcerations).

Considerable justification can be made for dropping the term SJS type II and simply referring to the condition as Stuve-Wiedemann syndrome. The disease is not technically that which Schwartz and Jampel described. Nevertheless, the term SJS type II is included in this discussion. Because so few patients with Stuve-Wiedemann syndrome have survived long term, most of the clinical information provided below pertains to SJS types IA and IB. Information pertinent to Stuve-Wiedemann syndrome will be identified as such. More genetic details of both diseases are provided in Causes.

Pathophysiology

The clinical features of muscle stiffness in SJS type I somewhat resemble those seen in myotonic disorders, stiff person syndrome, or Isaacs syndrome. The stiffness does not disappear with sleep or benzodiazepine treatment (as in stiff person syndrome), and it is not abolished reliably with curare (as in Isaacs syndrome).

Neurophysiologic examination typically shows continuous electrical activity (similar to myotonic discharges). However, the electrical activity often lacks the waxing and waning quality of true electrical myotonia and might be better described as complex, repetitive discharges. At other times, the pattern resembles neuromyotonia (ie, extremely rapid repetitive discharges that wane from an initially high amplitude). In other cases, a combination of these and other electrical patterns are seen. Perhaps a unique Schwartz-Jampel pattern exists that has not yet been fully defined.

Prior to the discovery of the specific gene defect, the similarity to myotonic disorders provoked speculation that a muscle ion channel abnormality or a muscle enzyme defect might underlie this condition. The fact that a defect exists in the gene for perlecan, a heparin sulfate proteoglycan that is the major proteoglycan of basement membranes and is present in cartilage, supports the general concept of a membrane abnormality and the presence of dysmorphic features. However, precise knowledge of why abnormal electrical discharges occur is still lacking. Perhaps the perlecan abnormality produces secondary membrane channel abnormalities. In addition, how this basement membrane defect actually causes the skeletal and other morphological problems is not understood.

No evidence indicates that the muscle pathology in Stuve-Wiedemann syndrome is similar, although the muscles are probably not normal. Abnormal accumulations of lipid droplets have been found in the muscles of persons with Stuve-Wiedemann syndrome (Di Rocco, 2003), although what this means remains unclear.

Frequency

United States

SJS types IA and IB are very rare, but the frequency is not actually known. Stuve-Wiedemann syndrome is probably even rarer.

International

Although SJS was initially described in the United States, it has also been reported internationally. Both SJS type I and Stuve-Wiedemann syndrome are rare throughout the world

Mortality/Morbidity

• SJS type IA does not significantly shorten lifespan. No definite data exist on whether type IB shortens lifespan. Type II definitely shortens lifespan, with most patients not surviving to adulthood.
• Much of the morbidity of SJS types IA and IB is related to the discomfort associated with the muscle stiffness and to problems with blepharospasm. As many as 20% of affected patients are mentally retarded. However, many patients are of normal or even superior intelligence. Skeletal abnormalities and other physical deformities may cause psychological morbidity in some individuals. Like a number of other myopathies, SJS is associated with an increased risk of malignant hyperthermia.

Race

No significant information is available on racial distribution.

Sex

SJS syndrome has been described in both males and females. However, data are insufficient to indicate any sexual predilection.

Age

SJS is an inherited disease and, thus, it is genetically present from conception. It is usually noticeable by the first year of life and frequently can be diagnosed at or soon after birth.

Clinical

History

• Muscles are clinically stiff and may be hypertrophic, although in some patients muscle mass may be diminished. The dysmorphic features, muscle stiffness, and muscle weakness are usually apparent to the patient's parents during the first year of life and, frequently, soon after birth.
• The stiffness is usually evident when the parents flex the child's limbs.
• The weakness takes the form of delay in achieving motor milestones. For example, walking frequently is delayed. Nevertheless, in most cases, the children do learn to walk and become entirely self-sufficient.
• When they are older, they notice the muscle stiffness, which is usually most severe in the thighs. Patients also report limitations of joint flexion in various joints, particularly the knees.
• Signs include narrow palpebral fissures with normal eyelid development, blepharospasm, and hypertrichosis of the eyelids (ie, excessive hair, multiple rows of hair); micrognathia; unusual flattened facies with a puckered facial appearance; and small muscle mass. Other skeletal and joint deformities include short neck, pectus carinatum (convex chest, ie, chest is bowed out), kyphosis (convex angulation of spine giving a humpback appearance), coxa valga (hip deformity involving increased neck-shaft angle of the femur), and irregularity of capital femoral epiphyses.
• According to one report, the incidence of mental retardation is high (20%), but most patients are of normal intelligence, and high intelligence is not incompatible with this condition.

Physical

• The dysmorphic features are usually evident.
• Most patients are short with narrow palpebral fissures (blepharophimosis), flattened facies, and micrognathia.
• Some patients show blepharospasm in addition to the blepharophimosis.
• Bony abnormalities include joint deformities and limitations of joint motion, coxa valga, irregularity of the capital femoral epiphyses, kyphosis, short neck, and pectus carinatum.
• The muscles are stiff and they can be either hypertrophic or reduced in mass.

Causes

• A multinational collaboration of scientists localized the gene defect for type I SJS to the 1p34-p36 region of chromosome 1 (Nicole, 1995). Further research showed that the specific gene affected was the gene for perlecan, which is a heparin sulfate proteoglycan, the major proteoglycan of basement membranes (Nicole, 2000). It is also involved in cartilage. The gene encoding for perlecan is called HSPG2. Nicole et al described 3 families with a mutation in the HSPG2 gene.
• Types IA and IB both involve a mutation of the perlecan gene.
• The only difference between types IB and IA is that type IB is more severe and, therefore, is usually diagnosed earlier.
• One factor that has impeded the further understanding of SJS type I is that until recently, very few patients had been studied genetically. Through 2005, only 8 patients from 6 families had been reported in molecular genetic studies.
  • Stum et al made a major addition to this literature with a molecular genetic study of 35 patients in 23 families (Stum, 2006). They found 22 new mutations. Most mutations were private (ie, limited to one particular family). Thus, no existence of a founder effect was suggested, whereby all (or a large percentage) of mutations could be presumed to derive from a single original case. The mutations included insertions and deletions and splice-site, missense, and nonsense mutations. Most of the mutations allowed for some level of functional protein production.
  • Often, a given patient has 2 different types of mutations, 1 of which allows a greater production of functional perlecan protein than the other. Based on the cases studied molecularly thus far, some level of functional perlecan protein production always seems apparent. Indeed, through alternative splicing, the normal protein may actually be produced, albeit at a lower level than normal.
  • In other cases, a functional but somewhat abnormal protein may be produced. Alternatively, a combination of different variants of perlecan could be produced, although at lower levels of functional protein than normal.
  • Thus, a significant amount of molecular heterogeneity exists, genomically and proteomically, within SJS type I.
• One would like to think that the molecular heterogeneity could explain the clinical heterogeneity, especially the existence of types IA and IB. In other words, it might be plausible that in type IA, more normal or, at least functional, protein is available than in type IB. So far, however, that has not been shown.
  • In addition, currently no known correlation exists between the specific mutations found and the specific features of a given case. However, the new mutations found by Stum et al in 2006 have been discovered so recently that not enough time has elapsed to explore such possibilities.
  • The new findings should be important tools to help find correlations among genetic variants, perlecan forms and levels, and clinical subtypes. Of course, other facts yet unknown also may influence the severity and the specific characteristics of the disease.
  • The new information does not immediately provide an explanation for the specific character of the problems (ie, the electrical membrane instability of the muscle, the specific dysmorphic features); however, now that many mutations are known, this knowledge can be a basis for future structural and functional correlations to better understand how the perlecan abnormalities cause the features of the disease and, perhaps, to find ways of ameliorating or even curing it.
• An additional molecular biological fact of interest related to perlecan is that another disease, called dyssegmental dysplasia of the Silverman-Handmaker type (DDSH), is also caused by a recessive mutation of the perlecan gene (Arikawa-Hirasawa, 2001). This disease is even rarer than SJS or Stuve-Wiedemann syndrome and even fewer cases have been studied molecularly.
  • In the few that have been studied, mutations that totally eliminate the ability to produce any functional protein product (ie, functionally null mutations) have been discovered. Therefore, whereas in SJS types IA and IB some level of functional (and often even normal) perlecan protein is always produced, in DDSH, none is produced.
  • Conceptually, one could argue that DDSH is a third type of SJS type I (eg, type IC)—the worst type. However, it is considered a separate disease for several reasons.
    • The dysplasia has a segmental quality characterized by significant variations in the shape and size of the vertebral bodies (anisospondyly). This is considered a defect in segmentation during development. This feature has been viewed as making it part of a possible spectrum of dyssegmental disorders, which would include another poorly understood disorder, Rolland-Desbuquois type of dyssegmental dwarfism (Fasanelli, 1985), which is similar to DDSH but somewhat less severe.
    • The dyssegmental dwarfisms also manifest cleft palate and encephalocele, which are not features of SJS. Although the short stature of patients with SJS implies some degree of shortness of limbs, SJS patients do not exhibit the marked limb shortness (micromelia) seen in dyssegmental dwarfism.
  • The issue of whether this is a separate disease is to some extent a question of classification, which could change if more fully studied clinical cases become available. For example, if mutations are found that produce levels of functional perlecan intermediate between those of SJS types I and DDSH and if the phenotype of such patients is also intermediate between the two, then considering them the same disease and just part of a spectrum dependent on the level of expression of functional perlecan would probably be justified. Indeed, no cases of the Rolland-Desbuquois type of dyssegmental dwarfism have been examined for perlecan mutations or for levels of functional perlecan protein expression and it would be very interesting to know whether this variant of dyssegmental dwarfism has a perlecan abnormality.
• Type II is not caused by the same genetic abnormality. The diseased gene in this case was mapped to band 5p13.1 at locus D5S418 (Dagoneau, 2004). By studying the genetic material of 19 patients who had been diagnosed with either Stuve-Wiedemann syndrome or SJS type II, they found that all patients had null mutations in their LIFR gene at the above-mentioned locus. This impaired the function of the JAK/STAT3 signaling pathway. Although the exact mutation was not identical in all 19 patients, the fact that the mutations all appeared to have the same molecular biological and biochemical effect led to the conclusion that Stuve-Wiedemann syndrome and SJS type II should be considered a single homogeneous disease.

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