Schwartz–Jampel Syndrome
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Schwartz–Jampel syndrome (SJS, also known as chondrodystrophic myotonia) is a rare
genetic disease A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosome abnormality. Although polygenic disorders are ...
caused by a mutation in the
perlecan Perlecan (PLC) also known as basement membrane-specific heparan sulfate proteoglycan core protein (HSPG) or heparan sulfate proteoglycan 2 (HSPG2), is a protein that in humans is encoded by the ''HSPG2'' gene. The HSPG2 gene codes for a 4,391 a ...
gene (''HSPG2'') which causes
osteochondrodysplasia An osteochondrodysplasia,Etymology: . or skeletal dysplasia, is a disorder of the development of bone and cartilage. Osteochondrodysplasias are rare diseases. About 1 in 5,000 babies are born with some type of skeletal dysplasia. Nonetheless, if t ...
associated with
myotonia Myotonia is a symptom of a small handful of certain neuromuscular disorders characterized by delayed relaxation (prolonged contraction) of the skeletal muscles after voluntary contraction or electrical stimulation, and the muscle shows an abnor ...
. Most people with Schwartz–Jampel syndrome have a nearly normal life expectancy.


Cause

Schwartz–Jampel syndrome is caused by mutations in the ''HSPG2'' gene, which makes the protein
perlecan Perlecan (PLC) also known as basement membrane-specific heparan sulfate proteoglycan core protein (HSPG) or heparan sulfate proteoglycan 2 (HSPG2), is a protein that in humans is encoded by the ''HSPG2'' gene. The HSPG2 gene codes for a 4,391 a ...
, which is found in muscle and
cartilage Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...
. Relationships between the disease and perlecan deficiency have been studied. In Schwartz–Jampel syndrome, it is suspected that abnormal perlecan function leads to a deficiency in
acetylcholinesterase Acetylcholinesterase (HUGO Gene Nomenclature Committee, HGNC symbol ACHE; EC 3.1.1.7; systematic name acetylcholine acetylhydrolase), also known as AChE, AChase or acetylhydrolase, is the primary cholinesterase in the body. It is an enzyme th ...
, an enzyme involved in breaking down the
neurotransmitter A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a Chemical synapse, synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotra ...
acetylcholine Acetylcholine (ACh) is an organic compound that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Par ...
, which incites muscle contraction. If acetylcholine is not broken down, it can lead to prolonged muscle contraction/stiffening of the muscles (
myotonia Myotonia is a symptom of a small handful of certain neuromuscular disorders characterized by delayed relaxation (prolonged contraction) of the skeletal muscles after voluntary contraction or electrical stimulation, and the muscle shows an abnor ...
). The condition is believed to follow an autosomal recessive inheritance pattern, although some reported cases suggest an autosomal dominant inheritance pattern.


Symptoms

Some signs and symptoms that are frequently exhibited in patients with SJS include epiphyseal abnormalities, metaphyseal abnormalities,
arthrogryposis multiplex congenita Arthrogryposis (AMC) describes congenital joint contracture in two or more areas of the body. It derives its name from Greek, literally meaning 'curving of joints' (', 'joint'; ', late Latin form of late Greek ', 'hooking'). Children born with one ...
, bowing of long bones, a protruding lower lip, full cheeks, a disturbed
gait Gait is the pattern of Motion (physics), movement of the limb (anatomy), limbs of animals, including Gait (human), humans, during Animal locomotion, locomotion over a solid substrate. Most animals use a variety of gaits, selecting gait based on s ...
,
genu valgum Genu valgum, commonly called "knock-knee", is a condition in which the knees angle in and touch each other when the human leg, legs are straightened. Individuals with severe valgus deformity, valgus deformities are typically unable to touch thei ...
, hip dysplasia,
hypertonia Hypertonia is a term sometimes used synonymously with ''spasticity'' and ''rigidity'' in the literature surrounding damage to the central nervous system, namely upper motor neuron lesions. Impaired ability of damaged motor neurons to regulate ...
, intellectual disability, joint stiffness, low-set posteriorly-rotated ears, metatarsus valgus, micromelia,
myotonia Myotonia is a symptom of a small handful of certain neuromuscular disorders characterized by delayed relaxation (prolonged contraction) of the skeletal muscles after voluntary contraction or electrical stimulation, and the muscle shows an abnor ...
, narrow mouth, flat foot, pursed lips, short stature, skeletal dysplasia,
trismus Trismus is a condition of restricted opening of the mouth. The term was initially used in the setting of tetanus. Trismus may be caused by spasm of the muscles of mastication or a variety of other causes. Temporary trismus occurs much more freque ...
, and visual impairment.


Diagnosis

Schwartz–Jampel syndrome is diagnosed on the basis of characteristic facial features, skeletal features and myotonia.
Blood tests A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a hypodermic needle, or via fingerprick. Multiple tests for specific blood components, such as a glucose test or a cho ...
may show elevated serum
creatine kinase Creatine kinase (CK), also known as creatine phosphokinase (CPK) or phosphocreatine kinase, is an enzyme () expressed by various tissues and cell types. CK catalyses the conversion of creatine and uses adenosine triphosphate (ATP) to create phos ...
or
aldolase Fructose-bisphosphate aldolase (), often just aldolase, is an enzyme catalyzing a reversible reaction that splits the aldol, fructose 1,6-bisphosphate, into the triose phosphates dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphat ...
.
X-rays An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...
,
muscle biopsy In medicine, a muscle biopsy is a procedure in which a piece of muscle tissue is removed from an organism and examined microscopically. A muscle biopsy can lead to the discovery of problems with the nervous system, connective tissue, vascular s ...
or
electromyography Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyo ...
(EMG) may be useful.
Genetic testing Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...
for the HSPG2 gene may confirm diagnosis.


Treatment

There is no cure for Schwartz–Jampel syndrome. Treatment is aimed at reducing muscle stiffness and cramping and may include massage, muscle warming and gradual strengthening exercises.
Muscle relaxants A muscle relaxant is a drug that affects skeletal muscle function and decreases the muscle tone. It may be used to alleviate symptoms such as muscle spasms, pain, and hyperreflexia. The term "muscle relaxant" is used to refer to two major therapeu ...
or
anti-seizure medications Anticonvulsants (also known as antiepileptic drugs, antiseizure drugs, or anti-seizure medications (ASM)) are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Anticonvulsants are also used in the treatment ...
, especially
carbamazepine Carbamazepine, sold under the brand name Tegretol among others, is an anticonvulsant medication used in the treatment of epilepsy and neuropathic pain. It is used as an adjunctive treatment in schizophrenia along with other medications and as ...
, may be used. Eye symptoms such as
blepharospasm Blepharospasm is a neurological disorder characterized by intermittent, involuntary spasms and contractions of the orbicularis oculi muscle, orbicularis oculi (eyelid) muscles around both eyes. These result in abnormal twitching or blinking, an ...
might be relieved by
Botox Botulinum toxin, or botulinum neurotoxin (commonly called botox), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon endi ...
. Otherwise, a variety of surgical procedures have been found to be effective.
Malignant hyperthermia Malignant hyperthermia (MH) is a type of severe reaction that occurs in response to particular medications used during general anesthesia, among those who are susceptible. Symptoms include muscle rigidity, fever, and a fast heart rate. Complica ...
, a potential complication of surgery, is a greater risk for people Schwartz–Jampel syndrome and an important consideration when considering surgery.


Prognosis

Most people with Schwartz–Jampel syndrome have a nearly normal life expectancy.


History

The syndrome was first described in 1962 by American
ophthalmologist Ophthalmology (, ) is the branch of medicine that deals with the diagnosis, treatment, and surgery of eye diseases and disorders. An ophthalmologist is a physician who undergoes subspecialty training in medical and surgical eye care. Following a ...
Oscar Schwartz and American neuro-ophthalmologist Robert Steven Jampel.


Society

In March 2013, there was media coverage of a British 7-year-old boy named Owen, with chronically tense muscles due to SJS, and his three-legged pet dog. They became first-place winners of the 2013
Crufts Crufts is an international dog show held annually in the United Kingdom, held since 1891, and organised by The Kennel Club. It is the largest show of its kind in the world. Crufts is primarily a championship conformation show for dogs, and ...
Kennel Club's annual ''Friends for Life'' competition, which "celebrates dogs that have truly earned the title of man’s best friend through bravery, support or companionship". The dog was also awarded ''The Braveheart Honour'' in the ceremony of The British Animal Honours in April 2013 ( ''Haatchi the dog''). The two are featured in the book ''Haatchi & Little B'' (2014, ) by Wendy Holden and on Haatchi's
Facebook Facebook is a social media and social networking service owned by the American technology conglomerate Meta Platforms, Meta. Created in 2004 by Mark Zuckerberg with four other Harvard College students and roommates, Eduardo Saverin, Andre ...
page. In 2016, 9-year-old Owen was featured in a
TLC TLC may refer to: Arts and entertainment Television * ''TLC'' (TV series), a 2002 British situational comedy television series that aired on BBC2 * TLC (TV network), formerly the Learning Channel, an American cable TV network ** TLC (Asia), an A ...
documentary A documentary film (often described simply as a documentary) is a nonfiction Film, motion picture intended to "document reality, primarily for instruction, education or maintaining a Recorded history, historical record". The American author and ...
series, ''Two in a Million'', in which he met and formed a friendship with Giovanni, a 7-year-old American boy with SJS.


References


External links

{{DEFAULTSORT:Schwartz-Jampel syndrome Skeletal disorders Rare diseases Genetic syndromes Syndromes