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|LETTERS TO EDITOR
|Year : 2019 | Volume
| Issue : 4 | Page : 1160-1162
Schwartz–Jampel Syndrome Mimicking Myotonia Congenita
Hansashree Padmanabha1, Thomas Mathew2, T Manjusha2
1 Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India
2 Department of Neurology, St Johns Medical College and Hospital, Bengaluru, Karnataka, India
|Date of Web Publication||10-Sep-2019|
Dr. Thomas Mathew
Department of Neurology, St Johns Medical College and Hospital, Bengaluru, Karnataka
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Padmanabha H, Mathew T, Manjusha T. Schwartz–Jampel Syndrome Mimicking Myotonia Congenita. Neurol India 2019;67:1160-2
Schwartz–Jampel syndrome (SJS) is a rare autosomal recessively an inherited congenital myotonia-like syndrome characterized by distinctive facial features, skeletal deformities, and muscle stiffness. The authors report a genetically confirmed case of SJS 1A in a 15-year-old boy manifesting only as isolated muscle stiffness mimicking myotonia congenita.
A 15-year-old boy presented to us with progressive difficulty in running, frequent falls in an uneven surface, and initial hesitancy in getting up from prolonged sitting posture noted from 10 years of age. Improvement of stiffness was noted on performing the repeated activity. Symptoms were not aggravated on exposure to cold, stress, or fever. No history of diurnal fluctuations was present. He was first born to a third-degree healthy consanguineous couple with an uneventful perinatal period. He had two younger siblings; 13-year-old boy with generalized muscle stiffness and 4-year-old girl with handgrip difficulties. On examination, he had normal anthropometry, no dysmorphism, generalized muscle hypertrophy with Herculean appearance, handgrip, eyelid and percussion myotonia, positive warm up phenomenon, Gowers' sign, and proximal weakness with diminished reflexes [Figure 1]a. Systemic examination was unremarkable. There was no evidence of dysmorphism in siblings, but they had clinical myotonia. Parents were asymptomatic [Figure 1]b. A clinical possibility of Becker variant of myotonia congenita was considered and all were initiated on oxcarbazepine. Investigations revealed mildly elevated creatine phosphokinase 720 U/L (26-308). Electrocardiogram, echo, and thyroid functions were normal. Nerve conduction study and skeletal survey were normal. Electromyography in vastus lateralis confirmed the presence of electrical myotonia with a characteristic dive-bomber sound. Targeted next-generation sequencing for myotonia panel revealed a previously unreported compound heterozygous mutation in Heparan Sulfate Proteoglycan 2 (HSPG2) gene, intronic variants [c.7874-47A>G] and [c.4030-85C>T]. Sanger sequencing further confirmed the pathogenicity. Genetic analysis of reported variant for parents and siblings could not be done due to affordability issues. Based on the clinical and genetic analysis, a final diagnosis of SJS 1A was considered.
|Figure 1: (a) Image of Index child showing no dysmorphism; (b) Family Pedigree|
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Both SJS 1A and myotonia congenita are important non-dystrophic causes of myotonia in childhood. SJS 1A is due to mutations in HSPG2 gene (located on chromosome 1p36.12, which encodes perlecan, a component of basement membrane). Defect in perlecan is known to cause chondrodysplasia, but the exact pathophysiology for myotonia in SJS 1A is uncertain. Myotonia congenita can either be autosomal dominant (Thomsen disease) or autosomal recessive (Becker disease). It is caused by mutations in voltage-gated chloride channel; CLCN1 gene is located on chromosome 7q34 that reduces the threshold for muscle membrane firing and leads to myotonia. Though both SJS 1A and myotonia congenita are known to cause clinical and electrical myotonia, with onset in childhood, and positive warm-up phenomenon, it is important to differentiate between the two for accurate genetic diagnosis and antenatal counseling.
SJS 1A in addition to muscle stiffness or myotonia has characteristic facial features and skeletal deformities. The facial features described in the literature include mask-like facies, blepharospasm with blepharophimosis, narrow palpebral aperture, pursed lips, bushy eyebrows, low set ears, high arched palate, long philtrum, and a pinched upturned nose., Mild-to-moderate skeletal deformities in SJS 1A include fixed contractures at elbow, knee, and ankle; metaphyseal dysplasia at hip and knee; kyphoscoliosis with lumbar lordosis; vertebral anomalies; and short stature., Muscle stiffness in myotonia congenita can be episodic with aggravation on cold exposure, stress, menstruation, and pregnancy. The unique features in the index child with genetically confirmed SJS1A is absence of the characteristic facial dysmorphism and skeletal deformities.
Our case highlights that SJS 1A can occasionally manifest purely with muscle stiffness. The hallmark features like dysmorphism and skeletal deformities might be absent in a few and targeted next-generation sequencing would be helpful in differentiating it from other causes of childhood myotonia.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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