L-tyrosine for treatment of an infant with nemaline rod myopathy.

Nemaline rod myopathy is an extremely rare muscle disease responsible for hypotonia and poor muscle strength in infants. The disease has variable phenotypic presentations across different ages, ranging from neonatal to the adult onset and from severe to asymptomatic varieties. Clinical features, muscle biopsy and genetic testing help in diagnosis. The histopathological examination shows the presence of rod-like structures or nemaline bodies in muscles. Management remains mainly supportive, and currently, there is no available curative treatment. This case report describes an infant presenting with gross hypotonia, poor handling of secretions and multiple extubation failures who was diagnosed by clinical exome sequencing. The patient harboured compound heterozygous variants in the NEB gene suggestive of nemaline rod myopathy. The newborn showed significant improvement in muscle strength after he was started on dietary L-tyrosine supplementation. This case highlights the emerging role of L-tyrosine in the supportive care of infants with nemaline rod myopathy.

Schaaf-Yang Syndrome: Clinical Phenotype and Effects of 4 years of Growth Hormone Treatment.

INTRODUCTION: Schaaf-Yang syndrome (SYS) is a rare neurodevelopmental disorder caused by truncating mutations of the MAGEL2 gene, located in the Prader-Willi syndrome (PWS) region. PWS and SYS have phenotypic overlap. Patients with SYS are often treated with growth hormone (GH), but evidence for the effectiveness of the treatment in patients with SYS is limited. METHODS: This study describes 7 children with SYS. We studied their phenotype, genotype, and the effect of GH treatment on height and body mass index (BMI) during 4 years and on body composition during 1 year. RESULTS: All patients had a normal birth weight. Most patients had hypotonia and feeding difficulties after birth (86%). Full-scale IQ ranged from <50 to 92. All patients above the age of 2 years had psycho-behavioral problems. There were no apparent correlations between the phenotype and the location of the defect in the MAGEL2 gene. Mean (95% CI) height SDS increased significantly from -1.74 (-3.55; 0.07) at start to -0.05 (-1.87; 1.77) after 4 years of GH treatment. Mean (95% CI) BMI SDS decreased significantly from 2.01 (1.02; 3.00) to 1.22 (0.18; 2.26) after 6 months and remained the same during the rest of the follow-up. Fat mass percentage SDS decreased and lean body mass did not change during 1 year of treatment in 3 patients. CONCLUSION: Patients presented with a phenotype of hypotonia, respiratory insufficiency, and feeding difficulties after birth, endocrine disorders, intellectual disability, and behavioral problems. Treatment with GH significantly improved height SDS and BMI over the course of 4 years.

Asfotase alfa improved skeletal mineralization and fracture healing in a child with MCAHS.

Tissue non-specific alkaline phosphatase (TNSALP) is an enzyme that is tethered to the cell membrane by glycosylphosphatidylinositol (GPI) and converts inorganic pyrophosphate to inorganic phosphate. Inorganic phosphate combines with calcium to form hydroxyapatite, the main mineral in the skeleton. When TNSALP is defective, conversion of inorganic pyrophosphate to inorganic phosphate is impaired and the skeleton is at risk of under-mineralization. Phosphatidylinositol glycan anchor biosynthesis class N (PIGN) is one of more than 20 genes in the GPI-biosynthesis family. Pathogenic variants in PIGN have been identified in multiple congenital anomalies-hypotonia-seizures syndrome (OMIM 614080), although a metabolic bone disease or skeletal fragility phenotype has not been reported. We describe a female child with multiple congenital anomalies-hypotonia-seizures syndrome due to a compound heterozygous pathogenic variant in PIGN who sustained a low-trauma distal femur fracture at age 7.4 years. We hypothesized that the GPI synthesis defect may result in metabolic bone disease from inadequate anchoring of TNSALP in bone and initiated asfotase alfa, a human bone-targeted recombinant TNSALP-Fc-deca-aspartate peptide, as it could bypass the PIGN genetic defect that possibly caused her skeletal fragility. Asfotase alfa was begun at 8.5 years. Baseline X-rays revealed mild rachitic findings of wrists and knees, which resolved by 5 months of treatment. Bone mineral density (BMD) assessed by dual-energy X-ray absorptiometry (DXA) showed mild improvement in spine, hip and total body less head after 16 months of treatment, while radius declined. She sustained additional low trauma fractures at right tibia and left humeral neck at 11 and 15 months into treatment, which healed quickly. Calcium, phosphorus, and parathyroid hormone levels have remained within the normal range over the 18 months of treatment. For adverse effect, she experienced a rash and discomfort in the first week of treatment which resolved with ibuprofen and diphenhydramine. She also developed subcutaneous fat atrophy. Overall, in this child with a compound pathogenic variant in PIGN, off-label use of asfotase alfa has been generally well tolerated with minimal side effects and resolution of rickets, but she continues to remain skeletally fragile.

The Effect of Combined Growth Hormone and a Gonadotropin-Releasing Hormone Agonist Therapy on Height in Korean 3-M Syndrome Siblings.

3-M syndrome is a rare autosomal recessive growth disorder characterized by severe growth retardation, low birth weight, characteristic facial features, and skeletal anomalies, for which three causative genes (CUL7, OBSL1, and CCDC8) have been identified. We herein report two Korean siblings with 3-M syndrome caused by two novel OBSL1 mutations, and describe the effect of a combined treatment with growth hormone (GH) and a gonadotropin-releasing hormone (GnRH) agonist. A 7-year-old girl with short stature (-3.37 standard deviation score, SDS) and breast budding presented with subtle dysmorphic features, including macrocephaly, frontal bossing, a triangular face, prominent philtrum, full lips, a short neck, and fifth-finger clinodactyly. GnRH stimulation test revealed a pubertal pattern and advanced bone age of 8 years and 10 months. Her older sister, aged 10 years and 9 months, had experienced an early menarche, and had an advanced bone age (13.5 years) and predicted adult height of 142 cm (-4.04 SDS). Targeted exome sequencing identified that the siblings had two heteroallelic mutations in OBSL1. Both siblings underwent a combination therapy with GH and a GnRH agonist. A height gain was noted in both siblings even after short-term treatment. To fully elucidate the effects of the combined therapy, a larger cohort should be analyzed following a longer treatment period. However, such an analysis would be challenging due to the rarity of this disease.

"Electrifying dysmorphology": Potassium channelopathies causing dysmorphic syndromes.

Potassium channels are a heterogeneous group of membrane-bound proteins, whose functions support a diverse range of biological processes. Genetic disorders arising from mutations in potassium channels are classically recognized by symptoms arising from acute channel dysfunction, such as periodic paralysis, ataxia, seizures, or cardiac conduction abnormalities, often in a patient with otherwise normal examination findings. In this chapter, we review a distinct subgroup of rare potassium channelopathies whose presentations are instead suggestive of a developmental disorder, with features including intellectual disability, craniofacial dysmorphism or other physical anomalies. Known conditions within this subgroup are: Andersen-Tawil syndrome, Birk-Barel syndrome, Cantú syndrome, Keppen-Lubinsky syndrome, Temple-Baraitser syndrome, Zimmerman-Laband syndrome and a very similar disorder called Bauer-Tartaglia or FHEIG syndrome. Ion channelopathies are unlikely to be routinely considered in the differential diagnosis of children presenting with developmental concerns, and so detailed description and photographs of the clinical phenotype are provided to aid recognition. For several of these disorders, functional characterization of the genetic mutations responsible has led to identification of candidate therapies, including drugs already commonly used for other indications, which adds further impetus to their prompt recognition. Together, these cases illustrate the potential for mechanistic insights gained from genetic diagnosis to drive translational work toward targeted, disease-modifying therapies for rare disorders.

[Nemaline rod myopathy treated with L-tyrosine to relieve symptoms in a neonate]. / Miopatía nemalínica tratada con L-tirosina para aliviar los síntomas en un recién nacido.

Nemaline myopathy (NM) is a heterogeneous disorder defined by the presence of rod-shaped structures known as nemaline bodies or rods. The diagnosis is based on muscle weakness, combined with visualization of nemaline bodies on muscle biopsy. There is no curative treatment for nemaline myopathy. Therapeutic strategies for this condition are symptomatic and empirical. Herein, we present a newborn with severe respiratory failure and generalized muscle weakness, who was diagnosed as NM by muscle biopsy. The patient experienced remarkable decrease in sialorrhea and improvement of spontaneous movements after L-tyrosine treatment. This case is presented to emphasize the importance of muscle biopsy in the differential diagnosis of severe hypotonia during neonatal period and a possible benefit of L-tyrosine supplementation for decreasing sialorrhea and restoring muscle strength.

La miopatía nemalínica es un trastorno heterogéneo definido por la presencia de estructuras con forma de bastones, conocidas como cuerpos nemalínicos (o bastones de nemalina). El diagnóstico se funda en la debilidad muscular, además de la visualización de cuerpos nemalínicos en la biopsia muscular. La miopatía nemalínica no tiene cura. Las estrategias terapéuticas para este trastorno son sintomáticas y empíricas. En este artículo, presentamos el caso de una recién nacida con insuficiencia respiratoria grave y debilidad muscular generalizada, a la que se le diagnosticó miopatía nemalínica a través de la biopsia muscular. La paciente tuvo una notable disminución de la sialorrea y una mejora de los movimientos espontáneos después del tratamiento con L-tirosina. Este caso se presenta para destacar la importancia de la biopsia muscular en el diagnóstico diferencial de la hipotonía grave durante el período neonatal y el posible beneficio del aporte suplementario de L-tirosina para disminuir la sialorrea y restaurar la fuerza muscular.

Effects of pneumoperitoneum on severe hypernatremia in an adult patient who underwent laparoscopic surgery of hydatid cysts.

We describe the first case of severe hypernatremia associated to laparoscopic surgery for hydatid cyst in an adult patient after the use of hypertonic saline solution with complete resolution. Severe hypernatremia is an unusual fact at the immediate postoperative period but may have fatal consequences for the patient and need immediate action. The patient reached a serum sodium concentration of 179 mmol/L without adverse effects after 6 days of treatment. Laparoscopy could play a crucial role in Na+ absorption due to high intraabdominal pressure caused by the pneumoperitoneum and its limitations to avoid peritoneal absorption of hypertonic saline solution. The relation between this surgical technique and the severe complication is discussed. More experience is needed in terms of safety for the patient.

The Chemical Chaperone Phenylbutyrate Rescues MCT8 Mutations Associated With Milder Phenotypes in Patients With Allan-Herndon-Dudley Syndrome.

Mutations in the thyroid hormone transporter monocarboxylate transporter 8 (MCT8) prevent appropriate entry of thyroid hormones into brain cells during development and cause severe mental retardation in affected patients. The current treatment options are thyromimetic compounds that enter the brain independently of MCT8. Some MCT8-deficient patients (e.g., those carrying MCT8delF501) will not be as severely affected as most others. We have shown that the MCT8delF501 protein has decreased protein stability but important residual function once it reaches the plasma membrane. We were able to rescue protein expression and the function of MCT8delF501 in a Madin-Darby canine kidney cell model by application of the chemical chaperone sodium phenylbutyrate (NaPB), a drug that has been used to treat patients with cystic fibrosis and urea cycle defects for extended periods of time. In the present study, we have extended our previous study and report on the NaPB-dependent rescue of a series of other pathogenic MCT8 mutants associated with milder patient phenotypes. We show that NaPB can functionally rescue the expression and activities of Ser194Phe, Ser290Phe, Leu434Trp, Arg445Cys, Leu492Pro, and Leu568Pro mutations in MCT8 in a dose-dependent manner. The soy isoflavone genistein, a dietary supplement, which was effective in MCT8delF501, was also effective in increasing the expression and transport of these MCT8 mutants; however, the effect size differed among mutants. Kinetic analyses revealed that the Michaelis constants of the mutants toward the primary substrate 3,3',5-triiodothyronine were not much different from the wild-type value, suggesting that these mutants are not impaired in their interaction with substrate but rather destabilized by the mutation and degraded.

Carbetocin at Cesarean delivery for labour arrest: a sequential allocation trial to determine the effective dose.

PURPOSE: The aim of this study was to estimate the effective dose 90% (ED90) of carbetocin to provide adequate uterine tone at Cesarean delivery (CD) for labour arrest. METHODS: We conducted a double-blind dose-finding study of carbetocin using a biased-coin up-and-down design in women undergoing CD for labour arrest under epidural anesthesia. Forty healthy term pregnant women who had received at least three hours of oxytocin infusion during labour were recruited for the study. Carbetocin was administered intravenously upon delivery of the anterior shoulder of the fetus. The first patient received 20 µg, and the dose for the subsequent patient was determined according to the response of the previous patient as per the biased-coin allocation scheme using increments or decrements of 20 µg (maximum 140 µg). Uterine tone was assessed by the obstetrician and rated as satisfactory or unsatisfactory throughout the intraoperative period. The primary outcome was satisfactory uterine tone with no need for additional uterotonic drugs intraoperatively. Secondary outcomes included use of additional uterotonic drugs postoperatively in the first 24 hr, estimated blood loss, and adverse effects. RESULTS: The ED90 of carbetocin to produce adequate uterine tone was estimated at 121 µg (95% confidence interval [CI]: 111 to 130; 99% CI: 108 to 133) using the truncated Dixon and Mood (DM) method. The isotonic estimator of ED90 was 140 µg; however, the observed response rate across all doses was < 90%. Also, the 95% CI of the DM estimator is likely to have lower than expected coverage, while the 99% CI may have about 90% coverage. Therefore, these results should be interpreted with caution. The overall median (range) estimated blood loss was 1,014 (104-2,436) mL. The overall incidence of hypotension and tachycardia were 45% and 57.5%, respectively. At a dose of 140 µg, the incidence of tachycardia and intraoperative arrhythmias was 76% and 14%, respectively. CONCLUSION: The ED90 of carbetocin at CD for labour arrest, as determined in our study, should be interpreted with caution since it may be underestimated. This dose is higher than the currently recommended dose of 100 µg at elective CD and should not be used routinely given the uncertainty regarding its efficacy and the high incidence of arrhythmias at higher doses. This trial was registered at ClinicalTrials.gov, number: NCT01725243.

In vitro and mouse studies supporting therapeutic utility of triiodothyroacetic acid in MCT8 deficiency.

Monocarboxylate transporter 8 (MCT8) transports thyroid hormone (TH) across the plasma membrane. Mutations in MCT8 result in the Allan-Herndon-Dudley syndrome, comprising severe psychomotor retardation and elevated serum T3 levels. Because the neurological symptoms are most likely caused by a lack of TH transport into the central nervous system, the administration of a TH analog that does not require MCT8 for cellular uptake may represent a therapeutic strategy. Here, we investigated the therapeutic potential of the biologically active T3 metabolite Triac (TA3) by studying TA3 transport, metabolism, and action both in vitro and in vivo. Incubation of SH-SY5Y neuroblastoma cells and MO3.13 oligodendrocytes with labeled substrates showed a time-dependent uptake of T3 and TA3. In intact SH-SY5Y cells, both T3 and TA3 were degraded by endogenous type 3 deiodinase, and they influenced gene expression to a similar extent. Fibroblasts from MCT8 patients showed an impaired T3 uptake compared with controls, whereas TA3 uptake was similar in patient and control fibroblasts. In transfected cells, TA3 did not show significant transport by MCT8. Most importantly, treatment of athyroid Pax8-knockout mice and Mct8/Oatp1c1-double knockout mice between postnatal days 1 and 12 with TA3 restored T3-dependent neural differentiation in the cerebral and cerebellar cortex, indicating that TA3 can replace T3 in promoting brain development. In conclusion, we demonstrated uptake of TA3 in neuronal cells and in fibroblasts of MCT8 patients and similar gene responses to T3 and TA3. This indicates that TA3 bypasses MCT8 and may be used to improve the neural status of MCT8 patients.

Altered behavioral performance and live imaging of circuit-specific neural deficiencies in a zebrafish model for psychomotor retardation.

The mechanisms and treatment of psychomotor retardation, which includes motor and cognitive impairment, are indefinite. The Allan-Herndon-Dudley syndrome (AHDS) is an X-linked psychomotor retardation characterized by delayed development, severe intellectual disability, muscle hypotonia, and spastic paraplegia, in combination with disturbed thyroid hormone (TH) parameters. AHDS has been associated with mutations in the monocarboxylate transporter 8 (mct8/slc16a2) gene, which is a TH transporter. In order to determine the pathophysiological mechanisms of AHDS, MCT8 knockout mice were intensively studied. Although these mice faithfully replicated the abnormal serum TH levels, they failed to exhibit the neurological and behavioral symptoms of AHDS patients. Here, we generated an mct8 mutant (mct8-/-) zebrafish using zinc-finger nuclease (ZFN)-mediated targeted gene editing system. The elimination of MCT8 decreased the expression levels of TH receptors; however, it did not affect the expression of other TH-related genes. Similar to human patients, mct8-/- larvae exhibited neurological and behavioral deficiencies. High-throughput behavioral assays demonstrated that mct8-/- larvae exhibited reduced locomotor activity, altered response to external light and dark transitions and an increase in sleep time. These deficiencies in behavioral performance were associated with altered expression of myelin-related genes and neuron-specific deficiencies in circuit formation. Time-lapse imaging of single-axon arbors and synapses in live mct8-/- larvae revealed a reduction in filopodia dynamics and axon branching in sensory neurons and decreased synaptic density in motor neurons. These phenotypes enable assessment of the therapeutic potential of three TH analogs that can enter the cells in the absence of MCT8. The TH analogs restored the myelin and axon outgrowth deficiencies in mct8-/- larvae. These findings suggest a mechanism by which MCT8 regulates neural circuit assembly, ultimately mediating sensory and motor control of behavioral performance. We also propose that the administration of TH analogs early during embryo development can specifically reduce neurological damage in AHDS patients.

[MCT8-specific thyroid hormone cell transporter deficiency: a case report and review of the literature]. / Deficiencia del transportador celular de hormona tiroidea MCT8: caso clinico y revision de la bibliografia.

INTRODUCTION: MCT8 is a specific transporter for the T4 and T3 thyroid hormones that allows their entry in the brain and other organs. Mutations in MCT8 (Allan-Herndon-Dudley syndrome) lead to a severe form of X-linked psychomotor retardation, which is characterised by elevated plasma T3 and low T4. AIM: We describe the first case diagnosed in Spain with this syndrome and review the published literature about this topic. We both review the various clinical presentations, genetic advances, differential diagnosis and therapeutic perspectives of this syndrome and propose a diagnostic algorithm for it. CASE REPORT: A 5 year-old boy, with a clinical picture compatible with Pelizaeus-Merzbacher disease. PLP1 gene sequencing showed no abnormalities. All the genetic and metabolic studies conducted were normal. Finally, a complete study of thyroid profile revealed abnormalities that were consistent with MCT8 transporter deficiency. The sequencing of the SLC16A2 gene (MCT8) showed a mutation in exon 3 and the study made at a cellular level, has confirmed that this mutation changes the properties of the protein. CONCLUSIONS: In the last five years, there have been many publications about this syndrome, with the identification of more than 50 families worldwide. It is important to both know and suspect this syndrome, because the diagnosis is easy, cheap and accessible (thyroid profile) and, although it has no specific treatment, early diagnosis prevents unnecessary testing and allows to offer genetic counseling to the families affected by it.

TITLE: Deficiencia del transportador celular de hormona tiroidea MCT8: caso clinico y revision de la bibliografia.Introduccion. El MCT8 es un transportador especifico para las hormonas tiroideas T4 y T3, que permite su entrada en el cerebro y otros organos. La deficiencia de MCT8, o sindrome de Allan-Herndon-Dudley, es un trastorno ligado a X que, generalmente, se presenta como un cuadro neurologico grave de inicio precoz, con un perfil tiroideo caracteristico (aumento de T3 y disminucion de T4 y rT3). Objetivo. Se presenta el primer caso diagnosticado en España con este sindrome y se revisa la bibliografia publicada, las distintas formas de presentacion clinica, los avances geneticos, el diagnostico diferencial y las perspectivas terapeuticas, y se propone un algoritmo diagnostico. Caso clinico. Varon de 5 años con un cuadro clinico compatible con una enfermedad de Pelizaeus-Merzbacher. La secuenciacion del gen PLP1 no mostro alteraciones. Todos los estudios metabolicos y geneticos realizados fueron normales. Finalmente, un estudio completo del perfil tiroideo revelo alteraciones compatibles con una deficiencia del transportador MCT8. La secuenciacion del gen SLC16A2 (MCT8) mostro una mutacion en el exon 3 y el estudio celular confirmo que esta mutacion cambia las propiedades de la proteina. Conclusiones. En los ultimos años se han multiplicado las publicaciones sobre este sindrome, con la identificacion de mas de 50 familias en el mundo. Es importante conocer este sindrome y sospecharlo, porque el diagnostico es facil, economico y accesible (perfil tiroideo), y, aunque no tiene tratamiento especifico, el diagnostico precoz evita pruebas innecesarias y permite ofrecer consejo genetico a las familias afectadas.

Success of repeat detrusor injections of botulinum a toxin in patients with severe neurogenic detrusor overactivity and incontinence.

OBJECTIVES: Detrusor injections with botulinum toxin type A are an effective treatment for neurogenic detrusor overactivity, lasting for 9-12 months. When the patients develop botulinum resistance, subsequent injections might be less effective. Repeat injections in patients with severe neurogenic detrusor overactivity and incontinence were studied. METHODS: Patients received Botox (300 UI) or Dysport (750 UI) injections. Clinical variables: satisfaction, anticholinergics use, mean and maximum bladder capacity, continence volume. Cystometric parameters: compliance, cystometric capacity, reflex volume. STATISTICS: Anova, chi2-tests; t-tests and paired t-tests (p=0.05). RESULTS: Forty-three men and 23 women (mean age 38.3 years; mean duration of lesion 9.2 years) were included. The interval between subsequent injections (on average 9-11 months) did not change significantly (p=0.5594). The satisfaction was high and anticholinergics use decreased substantially (p=0.0000). Significant improvements were found in clinical parameters and in cystometric capacity, for compliance only at the second treatment. The incidence of reflex contractions was significantly reduced. Four patients had transient adverse events after Dysport. CONCLUSIONS: Repeat injections with botulinum toxin type A are as effective as the first one. The cause for repeat treatment is relapse of overactive bladder symptoms.

[Potentialities of reflexotherapy in complex treatment of hypotonic states]. / Vozmozhnosti refleksoterapii v kompleksnom lechenii gipotonicheskikh sostoianii.

Methods of reflexotherapy in complex treatment of hypotonic state have significant advantage before traditional medicamentous therapy. Patients with hypotonic conditions which received traditional treatment are exposed to the greater risk in development of various forms cerebrovascular pathologies.

Clinical effects of locally delivered nicotine in obstructive sleep apnea syndrome.

Obstructive sleep apnea (OSA) is a common disorder characterized by disordered breathing and associated with increased mortality and cardiovascular morbidity. A factor in the pathogenesis of OSA is hypotonia of the upper airway muscles during sleep, resulting in occlusion of the upper airway. Nicotine may be a suitable drug because it is a stimulant of breathing and activity of oropharyngeal muscles. A novel delivery system, a nicotine tooth patch (NTP) that releases nicotine continuously, has been developed by Perio Products (Jerusalem, Israel). A 2-mg NTP achieved low plasma levels of nicotine with high saliva levels (62 microg/mL), presumably resulting in high nicotine levels in the oropharynx. The aim of this study was to evaluate the effect of two doses of NTP, 2 mg and 4 mg, on the clinical features in OSA. Ten subjects with OSA were admitted overnight and monitored by polysomnography at baseline and during two treatments. The treatments were blind and in a randomized order. After a 4.3-mg NTP, T(max) was 40 +/- 16 minutes, C(max) was 123 +/- 43 microg/mL, and terminal T(1/2) was 29 +/- 11 minutes in saliva. Substantial nicotine levels persisted in saliva for approximately 4 hours. There was no effect of nicotine on the apnea-hypopnea index, even during the first 4 hours when there were high levels of nicotine in saliva (26.4 +/- 11.6, 26.8 +/- 19.5, and 26.8 +/- 23), or on sleep stages. Eppworth Sleepiness Scale scores were lower with a 4.3-mg NTP (9.1 +/- 4.5, 9.1 +/- 7.7, and 5.9 +/- 6.5). Locally delivered nicotine at the doses used had no significant effect on OSA.

Parálisis flácida e hipokalemia en un joven de 17 años / Flaccid paralysis and hypokalemia in a young man of 17 years old

Se presenta un paciente de 17 años que ingresa por un cuadro de tetraplejía, con conservación de la movilidad de los músculos de la cara y con valores de K de 1.5 meq/1. El cuadro clínico revierte en forma completa con la terapéutica de reposición de K, realizándose el diagnóstico de Parálisis Periódica Hipokalémica por biopsia muscular. La falta de antecedentes familiares, así como también la ausencia de enfermedades que pudieran ocasionar Parálisis Periódica Esporádica, nos llevó al diagnóstico de Parálisis Periódica Esporádica Idiopática

[Isolated proximal muscular weakness disclosing myasthenic syndrome]. / Faiblesse musculaire proximale isolée révélatrice d'un syndrome myasthénique.

Three cases of chronic limb-girdle myasthenia gravis (one man and two women) are reported. The duration of the disease was three, five and 20 years respectively. None had oculobulbar weakness during this period nor fluctuating symptoms. The primary diagnosis was myopathy in two cases and myelopathy in the other one. In view of this diagnosis, several features were atypical: absence of marked wasting, preservation of tendon reflexes and normal serum creatine kinase activity. Finally, diagnosis of myasthenia gravis was established by the occurrence of a characteristic decremental muscular response to repetitive stimulation and by positive edrophonium test. It seems that the rate of positivity of acetylcholine receptor antibody is lower than in the common form of the disease. Two patients responded to acetylcholinesterase inhibitors and one to high-doses intravenous human immunoglobulins. These and previous cases described in the literature raise the problem of the definition of an unusual form of myasthenia gravis or of a new type of neuromuscular disease characterized by the presence of distinctive changes on muscular biopsies, specially tubular aggregates as in one of our cases. However, this unusual form of chronic limb-girdle weakness has to be recognized because treatments are effective in most cases.