OCT and IOP findings in a healthy worker cohort: results from a teleophthalmic study in occupational medicine.

PURPOSE: To avoid significant loss of vision in employees, the working population could be examined with ophthalmic methods as OCT and IOP measurement for detection of serious eye diseases. The value of "virtual eye clinics" in occupational preventive medicine has been previously shown. We used a telemedical approach to gather epidemiological information about prevalence of eye diseases such as glaucoma, ocular hypertension, hypertensive retinopathy, diabetic retinopathy, epiretinal membrane, AMD, adult vitelliform maculopathy, cystoid maculopathy, choroidal nevi, and macular drusen. METHODS: The study included 931 people ranging from age 39 to 65 years. Using a telemedical approach, all medical examinations and the ophthalmic examination were performed by a technician using an optical coherence tomography (SD-OCT) and a pulse air tonometer. The data were saved in the web-based patient chart MedStage® of the Talkingeyes® Collaboration Network. RESULTS: We found a high prevalence of eye diseases in a group representative for the working-age population by telemedical examination. 13.47% of the workers examined showed ocular findings necessitating treatment or control by an ophthalmologist, including ocular hypertension (5.7%), hypertensive retinopathy with loss of temporal retinal nerve fiber thickness (2.3%), epiretinal membrane (1.07%), glaucoma (0.97%), age-related macular degeneration and adult vitelliform maculopathy (0.53%), and diabetic retinopathy (0.2%). Two of the examined persons presented ocular findings requiring urgent treatment to prevent serious vision loss. CONCLUSION: Using a telemedical approach, we collected epidemiological information about prevalence of eye diseases in the working-age population. Virtual eye clinics in occupational preventive medicine are a useful method to improve sight and reduce vision loss of workers by reducing travel time and inconvenience associated with an in-person appointment with an ophthalmologist.

Effects of S906T polymorphism on the severity of a novel borderline mutation I692M in Nav 1.4 cause periodic paralysis.

Hyperkalemic periodic paralysis (HyperPP) is a dominantly inherited muscle disease caused by mutations in SCN4A gene encoding skeletal muscle voltage gated Nav 1.4 channels. We identified a novel Nav 1.4 mutation I692M in 14 families out of the 104 genetically identified HyperPP families in the Neuromuscular Centre Ulm and is therefore as frequent as I693T (13 families out of 14 HyperPP families) in Germany. Surprisingly, in 13 families, a known polymorphism S906T was also present. It was on the affected allele in at least 10 families compatible with a possible founder effect in central Europe. All affected members suffered from episodic weakness; myotonia was also common. Compared with I692M patients, I692M-S906T patients had longer weakness episodes, more affected muscles, CK elevation and presence of permanent weakness. Electrophysiological investigation showed that both mutants had incomplete slow inactivation and a hyperpolarizing shift of activation which contribute to membrane depolarization and weakness. Additionally, I692M-S906T significantly enhanced close-state fast inactivation compared with I692M alone, suggesting a higher proportion of inactivated I692M-S906T channels upon membrane depolarization which may facilitate the initiation of weakness episodes and therefore clinical manifestation. Our results suggest that polymorphism S906T has effects on the clinical phenotypic and electrophysiological severity of a novel borderline Nav 1.4 mutation I692M, making the borderline mutation fully penetrant.

Lung ventilation volumetry with same-breath acquisition of hyperpolarized gas and proton MRI.

The purpose of this work was to assess the reproducibility of percentage of ventilated lung volume (PV) measured from hyperpolarized (HP) (3)He and (1)H anatomical images acquired in the same breath-hold when compared with PV measured from (3)He and (1)H images from separate breath-holds. Volumetric (3)He ventilation and (1)H anatomical images of the same resolution were acquired during the same breath-hold. To assess reproducibility, this procedure was performed twice with a short gap between acquisitions. In addition, (1)H images were also acquired in a separate breath for comparison. PV ((3)He ventilated volume divided by (1)H total lung volume) was calculated using the single-breath-hold images (PV(single)) and the separate-breath-hold images (PV(separate)). Short-term reproducibility of PV measurement was assessed for both single- and separate-breath acquisitions. Dice similarity coefficients (DSCs) were calculated to quantify spatial overlap between (3)He and (1)H segmentations for the single- and separate-breath-hold acquisitions. The efficacy of using the separate-breath method combined with image registration was also assessed. The mean magnitude difference between the two sets of PV values (±standard deviation) was 1.49 ± 1.32% for PV(single) and 4.19 ± 4.10% for PV(separate), with a significant difference (p < 0.01). The mean magnitude difference between the two PV values for the registered separate-breath technique (PV(sep-registered)) was 2.27 ± 2.23%. Bland-Altman analysis showed that PV measured with single-breath acquisitions was more repeatable than PV measured with separate-breath acquisitions, regardless of image registration. DSC values were significantly greater (p < 0.01) for single-breath acquisition than for separate-breath acquisition. Acquisition of HP gas ventilation and (1)H anatomical images in a single breath-hold provides a more reproducible means of percentage lung ventilation volume measurement than the previously used separate-breath-hold scan approach, and reduces errors.

Contractile elements in muscular fascial tissue - implications for in-vitro contracture testing for malignant hyperthermia.

Malignant hyperthermia is a dreaded complication of general anaesthesia. Predisposed individuals can be identified using the standardised caffeine/halothane in-vitro contracture test on a surgically dissected skeletal muscle specimen. Skeletal muscle is composed of muscle fibres and interwoven fascial components. Several malignant hyperthermia-associated neuromuscular diseases are associated with an altered connective tissue composition. We analysed adjacent fascial components of skeletal muscle histologically and physiologically. We investigated whether the fascial tissue is sensitive to electrical or pharmacological stimulation in a way similar to the in-vitro contracture test for diagnosing malignant hyperthermia. Using immunohistochemical staining, α-smooth muscle actin-positive cells (myofibroblasts) were detected in the epi-, endo- and perimysium of human fascial tissue. Force measurements on isolated fascial strips after pharmacological challenge with mepyramin revealed that myofascial tissue is actively regulated by myofibroblasts, thereby influencing the biomechanical properties of skeletal muscle. Absence of electrical reactivity and insensitivity to caffeine and halothane suggests that, reassuringly, the malignant hyperthermia diagnostic in-vitro contracture test is not influenced by the muscular fascial tissue.

Prevention of neural tube defects by folic acid - awareness among women of childbearing age in Slovakia.

BACKGROUND: Folic acid deficiency plays a central role in the aetiology of many congenital anomalies including neural tube defects. Protective effect of folic acid on embryo may be acquired only if taken periconceptionally. OBJECTIVES: The aim of the study was to investigate the awareness about folic acid among women of childbearing age in Bratislava, Slovakia. METHODS: There were 130 respondents involved in the research (106 pregnant women, 24 female students of medical faculty). Using questionnaire we acquired following data: pregnancy details, interest in diet before and during pregnancy, recommendations regarding nutrition and supplementation pre- and post-conception, knowledge about folic and other acid in 2004 and 2009. RESULTS: More than half of the respondents knew the sources of folic acid. The interest in the nutrition facts of the food dropped from 91 % to 58.5 %. The number of pregnant women advised about correct nutrition and folic acid supplementation before and during pregnancy increased from 16 % to 37 %. Planning the next gravidity with folic acid supplementation became greater than 21 % (38 % in 2009). Nevertheless, only 46 % of these women believed that proper food content with folic acid may prevent congenital anomalies. In a group of students planning to take folic acid periconceptionally the number raised up to 62.5 %. CONCLUSION: The results revealed low knowledge about the effect of folic acid on developing embryo among women of childbearing age. Effective intervention programs are needed with the aim to improve periconceptional intake of folic acid in 2004 and 2009. The results in both periods show low knowledge about this essential vitamin (Tab. 1, Fig. 8, Ref. 31).

In vitro muscle contracture investigations on the malignant hyperthermia like episodes in myotonia congenita.

BACKGROUND: A common form of congenital myotonia, myotonia congenita (MC), is caused by mutations in the skeletal muscle Cl(-) channel gene type 1 (CLCN1). Due to the reduced Cl(-) conductance of the mutated channels, the patients may develop generalized muscle rigidity and hypermetabolism during general anaesthesia. The clinical symptoms resemble malignant hyperthermia (MH), which may lead to mistreatment of the patient. METHODS: Muscle specimens of ADR mice (an animal model of MC) as well as of human individuals were used and exposed to potent ryanodine receptor type 1 (RyR1) activators and increasing K(+) concentration. Muscle force was monitored by a standardized diagnostic method for MH, the so-called in vitro contracture test. RESULTS: Neither muscle of ADR mice nor MC muscle (murine and human myotonic muscle) showed pathological contractures after exposure to the potent RyR1 agonists caffeine and halothane. Increasing concentrations of K(+) had a dose-dependent preventive effect on myotonic stiffness. CONCLUSION: We conclude that the adverse anaesthetic MH-like episodes observed in MC patients do not primarily originate from an altered Ca(2+) release in skeletal muscle. In MC muscle, this hypermetabolism is facilitated by a (pharmacologically induced) sustained depolarization due to an instable membrane potential. The in vitro results suggest that these patients benefit from tight K(+) monitoring because of the membrane potential stabilizing effect of K(+) .

Perlecan, the major proteoglycan of basement membranes, is altered in patients with Schwartz-Jampel syndrome (chondrodystrophic myotonia).

Schwartz-Jampel syndrome (SJS1) is a rare autosomal recessive disorder characterized by permanent myotonia (prolonged failure of muscle relaxation) and skeletal dysplasia, resulting in reduced stature, kyphoscoliosis, bowing of the diaphyses and irregular epiphyses. Electromyographic investigations reveal repetitive muscle discharges, which may originate from both neurogenic and myogenic alterations. We previously localized the SJS1 locus to chromosome 1p34-p36.1 and found no evidence of genetic heterogeneity. Here we describe mutations, including missense and splicing mutations, of the gene encoding perlecan (HSPG2) in three SJS1 families. In so doing, we have identified the first human mutations in HSPG2, which underscore the importance of perlecan not only in maintaining cartilage integrity but also in regulating muscle excitability.

Omphalocele with ectopic liver forming a mesodermal cyst.

BACKGROUND: Congenital anomalies of the abdominal wall are classified as anomalies with the abdominal wall defect (omphalocele, gastroschisis) and without the defect (umbilical hernia, persistent ductus omphaloentericus or urachus). Clinical presentations of these conditions are different, and so is the timing of surgical intervention and approach with or without the exploration of the peritoneal cavity. CASE: The presented case report refers to a rare finding of ectopic liver forming mesodermal cyst within the umbilical region. Full term neonate girl with 5 cm spheroid tumor in umbilicus was otherwise without problems. Ultrasonography (USG) of the lesion detected a tissue with good vascularization and a cystic cavity. There was no flow in the umbilical vessels and no evidence of intestinal loop in the sac. USG of the liver was normal. During surgery an additional narrow canaliculus was identified connecting the spheroid along with umbilical vessels to the liver. The whole spheroid together with the canaliculus was surgically removed without exploration of the abdominal cavity. Histological evaluation of the surgical specimen discovered liver tissue with a mesodermal cyst in the center. The sphere was connected to the liver by a bile duct. Six months after the operation the child is in a good clinical condition. CONCLUSION: In conclusion omphalocele may contain liver. Ectopic liver is an extremely rare condition. Surgical treatment in the presented case focused only on umbilicus without exploration of the abdominal cavity and appeared to be sufficient. Long-term postoperative follow up typical in pediatrics will be applied also in this patient (Fig. 3, Ref. 25).

Laparoscopic cholecystectomy in children.

UNLABELLED: In 95 children (age 6-18 y) treated for gallstones between 2002-2010, 95 laparoscopic cholecystectomies were carried out. Symptomatic cholecystolithiasis was the indication for laparoscopic cholecystectomy in most of the cases. In three patients, there was a conversion to open cholecystectomy. Postoperative complications due to failure of bile drainage arose in three patients. Restored bile drainage was secured for two biliodigestive anastomosis. Bile leak in a third patient solved a temporary biliary stent. Laparoscopic cholecystectomy is the gold standard for gallstones (Ref. 8). KEYWORDS: gallstones, laparoscopic cholecystectomy, cholecystolithiasis, bile drainage.

Objective visual field determination in forensic ophthalmology with an optimized 4-channel multifocal VEP perimetry system: a case report of a patient with retinitis pigmentosa.

We present the case of a 59-year-old male patient with progressive vision impairment and consecutive visual field narrowing ("tunnel view") for 7 years and a known retinitis pigmentosa for 5 years. The remaining Goldmann perimetric visual field at time reported was less than 5°. A request for blindness-related social benefits was rejected because an ophthalmologic expert assessment suggested malingering. This prompted us to assess an objective determination of the visual field using multifocal VEPs. Objective visual field recordings were performed with a four-channel multifocal VEP-perimeter using 58 stimulus fields (pattern reversal dartboard stimulus configuration). The correlated signal data were processed using an off-line method. At each field, the recording from the channel with the maximal signal-to-noise ratio (SNR) was retained, thus resulting in an SNR optimized virtual recording. Analysis of VEP signals was performed for each single field and concentric rings and compared to an average response measured in five healthy subjects. Substantial VEP responses could be identified in three fields within the innermost ring (eccentricity, 1.7°) for both eyes, although SNR was generally low. More eccentric stimuli did not elicit reliable VEP responses. The mfVEP recording was correlated with perimetric visual field data. The current SNR optimization by using the channel with the largest SNR provides a good method to extract useful data from recordings and may be appropriate for the use in forensic ophthalmology.

Retinal disorders in northern Brazilian patients treated with chloroquine assessed by multifocal ERG.

The effects of chloroquine intake on the retinal function in a Brazilian population of patients were assessed by multifocal electroretinography. Twenty-four randomly chosen eyes of patients treated with chloroquine for rheumatoid arthritis and systemic lupus erythematosus were examined using multifocal electroretinography (mfERG). Control measurements were acquired from 21 randomly chosen eyes of age-matched healthy subjects. None of the study participants had an inherited retinal disease or a Snellen visual acuity reduced to less than 20/40. In patients and control subjects, cumulative chloroquine dose, total daily dose, duration of treatment, retinal examination, visual field defects, visual acuity, and the mfERG were assessed. The average amplitudes and implicit times of the N1, P1, and P2 components of the mfERGs were measured in the central hexagon (R1) and in five rings (R2-R6). The values measured in patients and normal subjects were compared. The P1 amplitudes in R2 were significantly decreased in the patients. In addition, the amplitudes of N1 and N2 in R1 were significantly smaller in the patients. The implicit times of none of the components were significantly different between patients and controls. The response amplitude was not significantly correlated with cumulative dose and duration of intake. There was no correlation with retinal appearance, visual field, and visual acuity. In agreement with earlier data, the central mfERG amplitudes were decreased in chloroquine patients indicating functional alterations in the retina. These changes are also present in a Brazilian population suggesting that the effects of chloroquine are general and that genetic background and life circumstances probably have, if at all, only little effect.

A novel N440K sodium channel mutation causes myotonia with exercise-induced weakness--exclusion of CLCN1 exon deletion/duplication by MLPA.

We report a 4-generation Turkish family with 10 affected members presenting with myotonia and potassium- and exercise-induced paralytic attacks. The clinical presentation was neither typical for the chloride channel myotonias Thomsen and Becker nor for the separate sodium channel myotonia entities potassium-aggravated myotonia, paramyotonia congenita, and hyperkalemic periodic paralysis. It is best described by a combination of potassium-aggravated myotonia and hyperkalemic periodic paralysis. We excluded exonic chloride channel mutations including CLCN1 exon deletion/duplication by MLPA. Instead we identified a novel p.N440K sodium channel mutation that is located at the inner end of segment S6 of repeat I. We discuss the genotype phenotype relation.

[Muscle channelopathies. Myotonias and periodic paralyses]. / Muskuläre Kanalopathien. Myotonien und periodische Paralysen.

The myotonias and familial periodic paralyses are muscle channelopathies. They have in common an impaired muscle excitation that is caused by mutations in voltage-gated Na(+), K(+), Ca(2+), and Cl(-) channels. Membrane hyperexcitability usually results in myotonic stiffness; with increasing membrane depolarization hyperexcitability can be transiently turned into hypoexcitability causing transient weakness as in severe myotonia. Hypoexcitability due to long-lasting depolarization that inhibits action potential generation is the common mechanism for the periodic paralyses. Interictally, the ion channel malfunction may be compensated, so that specific exogenous or endogenous provocative factors are required to produce symptoms in the patients. An especially obvious triggering agent is the level of serum potassium, the ion decisive for resting membrane potential and degree of excitability. Periodic paralysis mutations for which the ion channel malfunction is not fully compensated interictally cause progressive myopathy.

[Epidemiology of neural tube defects]. / Epidemiológia defektov neurálnej rúry.

INTRODUCTION: Neural tube defects represent group of congenital diseases with relatively high incidence in population. Authors assess world and Slovak literature and statistical facts about the epidemiology of NTD and compare them with their own results of retrospective study performed in Children's Hospital, Bratislava. MATERIALS AND METHODS: List of patients consists of 250 children (106 boys, 144 girls): X-ray images showing lumbo-sacral part of vertebral column were evaluated retrospectively (X-ray of native abdomen, urological tract or skeleton). Authors assessed presence or non-presence of spina bifida on images, without relation to age, gender or diagnosis of patients. RESULTS: From the total number of 250 radiograms, 72 findings were positive (36 boys and 36 girls), 160 images were negative, 18 were unsuitable for evaluation due to low image quality. The highest diagnostic capture was from urological images - 40% of all positive findings. Incidence of spina bifida in Children's Hospital concluded from X-ray images is quite high - 28.8%. CONCLUSION: According to the data from National Centre of Health Statistics the incidence of open caudal neural tube defects in Slovakia is under 5 per 10 000 live-born children at present time. However the occurrence of occult spina bifida is not known exactly. The high rate of spina bifida presented herein (28%) can be caused by relatively low number of evaluated radiograms. Also the fact that children were not only healthy ones and data were obtained from the western part of Slovakia as well. In conclusion we can say that after accidental finding of caudal neural tube defect consecutive diagnostics should be performed in clinical positive cases - genetics, MRI and consultation with specialists to decide for the optimal follow up of the patient.

Recovery of mechano-electrical transduction in rat cochlear hair bundles after postnatal destruction of the stereociliar cross-links.

Mechano-electrical transduction (MET) in the stereocilia of outer hair cells (OHCs) was studied in newborn Wistar rats using scanning electron microscopy to investigate the stereociliar cross-links, Nomarski laser differential interferometry to investigate stereociliar stiffness and by testing the functionality of the MET channels by recording the entry of fluorescent dye, FM1-43, into stereocilia. Preparations were taken from rats on their day of birth (P0) or 1-4 days later (P1-P4). Hair bundles developed from the base to the apex and from the inner to outer OHC rows. MET channel responses were detected in apical coil OHCs on P1. To study the possible recovery of MET after disrupting the cross-links, the same investigations were performed after the application of Ca(2+) chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) and allowing the treated samples to recover in culture medium for 0-20 h. We found that the structure and function were abolished by BAPTA. In P0-P1 samples, structural recovery was complete and the open probability of MET channels reached control values. In P3-P4 samples, complete recovery only occurred in OHCs of the outermost row. Although our results demonstrate an enormous recovery potential of OHCs in the postnatal period, the structural component restricts the potential for therapy in patients.

Expression of the lipid transporters ABCA3 and ABCA1 is diminished in human breast cancer tissue.

ATP-binding cassette transporters ABCA3 and ABCA1 are related to a differentiated, lipid-secreting phenotype of type II pneumocytes. Since mammary gland epithelial cells also show pronounced lipid metabolism and secretion, we investigated the expression of these proteins in normal as well as in neoplastic breast tissue. Normal human breast tissue, breast cancer cell lines, and 162 tumor samples of patients with primary unilateral invasive breast cancer were analyzed for ABCA3 and ABCA1 protein expression by immunohistochemistry using tissue microarrays. Strong ABCA3 and ABCA1 expression was found in the inner layer of normal mammary gland epithelium. Concurrent cytoplasmic ABCA3 and ABCA1 immunoreactivity was found in 9 of 11 breast cancer cell lines. ABCA3 and ABCA1 were shown to be differentially expressed in human breast cancer. Loss of ABCA3 staining was significantly associated with positive nodal status and negative progesterone receptor expression. In multivariate analysis, diminished ABCA3 expression proved to be a significant, independent and adverse risk factor for tumor recurrence. ABCA1 expression was associated with positive lymph nodes, but not significantly associated with tumor recurrence or breast cancer-specific survival. ABCA3 and ABCA1 are strongly expressed in normal mammary gland epithelium. Decreased ABCA3 expression in breast cancer seems to be associated with poor prognosis.

State of the art in hereditary muscle channelopathies.

A combination of electrophysiological and genetic studies has resulted in the identification of several skeletal muscle disorders to be caused by pathologically functioning ion channels and has led to the term channelopathies. Typical hereditary muscle channelopa thies are congenital myasthenic syndromes, non-dystrophic myotonias, periodic paralyses, malignant hyperthermia, and central core disease. Most muscle channelopathies are commonly considered to be benign diseases. However, life-threatening weakness episodes or progressive permanent weakness may make these diseases severe, particularly the periodic paralyses (PP). Even in the typical PP forms characterized by episodic occurrence of weakness, up to 60% of the patients suffer from permanent weakness and myopathy with age. In addition, some PP patients present with a predominant progressive muscle weakness phenotype. The weakness can be explained by strongly depolarized fibers that take up sodium and water and that are electrically inexcitable. Drugs that repolarize the fiber membrane can restore muscle strength and may prevent progression.

[Type II bile duct cyst or accessory gall bladder?]. / Cysta choledochu II. typu alebo nadpocetný zlcník?

Choledochal and bile duct's cysts are well known, their morphological classification and also operative management had been described in detail. The most frequent are cysts' types I. and IV., in which the operation consists of cyst's resection and biliary tract reconstruction. Authors summarize nowadays knowledge and present case of 21-months old girl, who was diagnosed of choledochal cyst accidentally. She was operated on electively; the operative finding verified 2 cystic lesions with own bile ducts joined to choledochal duct. The proximal cyst had 3 diverticles and thus mimicked a choledochal cyst type IV. on the preoperative examinations. The resection of both cystic lesions was done. This is a unique case of biliary tract malformations.

[Clinical condition of patients with neural tube defects]. / Klinický stav pacientov s defektami neurálnej rúry.

INTRODUCTION: Neural tube defects are the most common congenital anomalies of central nervous system. Their onset is at the embryonic age of 21 to 28 days. Periconceptional administration of folic acid may reduce the occurrence of neural tube defects up to 70%. Clinical features depend on localization of the defect and malformation of central nervous system, as well as on intensive multidisciplinary care in early stages of development. Open defects (meningomyelocele) present with more severe neurological deficiency early after birth. Closed defect manifestation occurs usually later in life with tethered cord syndrome. PURPOSE: This study evaluates clinical status of the patients with neural tube defects, who are followed in the Children's Faculty Hospital in Bratislava. METHODS: Cross-sectional and also retrospective study was conducted by questionnaire that was given to mothers of children with neural tube defect. Data about perinatal and family history, occurrence of hydrocephalus, scoliosis, joint deformities, dysfunction of urinary system and bowel, as well as social care, were collected. Clinical features were statistically evaluated depending on beginning of the defect or locomotion status. RESULTS: 94 patients with mean age of 12.7 years +/- 6.59 SD were included in the study. Patients with open defects had more severe neurological deficiency with hydrocephalus, more common epilepsy, skeleton deformities, wheelchair-dependency, and dysfunction of urinary tract and bowel. Scoliosis and ability of locomotion significantly correlated with higher lever of defect, while hydrocephalus, continence, urinary infections, clean intermittent catheterization, constipation, scoliosis and joint deformities significantly correlated with the ability of locomotion (p < 0.05). CONCLUSION: For patients with neural tube defects, the level of neurological deficiency is the most important prognostic factor for many other clinical characteristics.

The skeletal muscle chloride channel in dominant and recessive human myotonia.

Autosomal recessive generalized myotonia (Becker's disease) (GM) and autosomal dominant myotonia congenita (Thomsen's disease) (MC) are characterized by skeletal muscle stiffness that is a result of muscle membrane hyperexcitability. For both diseases, alterations in muscle chloride or sodium currents or both have been observed. A complementary DNA for a human skeletal muscle chloride channel (CLC-1) was cloned, physically localized on chromosome 7, and linked to the T cell receptor beta (TCRB) locus. Tight linkage of these two loci to GM and MC was found in German families. An unusual restriction site in the CLC-1 locus in two GM families identified a mutation associated with that disease, a phenylalanine-to-cysteine substitution in putative transmembrane domain D8. This suggests that different mutations in CLC-1 may cause dominant or recessive myotonia.