A novel ATP1A2 mutation in a patient with hypokalaemic periodic paralysis and CNS symptoms.

Hypokalaemic periodic paralysis is a rare genetic neuromuscular disease characterized by episodes of skeletal muscle paralysis associated with low serum potassium. Muscle fibre inexcitability during attacks of paralysis is due to an aberrant depolarizing leak current through mutant voltage sensing domains of either the sarcolemmal voltage-gated calcium or sodium channel. We report a child with hypokalaemic periodic paralysis and CNS involvement, including seizures, but without mutations in the known periodic paralysis genes. We identified a novel heterozygous de novo missense mutation in the ATP1A2 gene encoding the α2 subunit of the Na+/K+-ATPase that is abundantly expressed in skeletal muscle and in brain astrocytes. Pump activity is crucial for Na+ and K+ homeostasis following sustained muscle or neuronal activity and its dysfunction is linked to the CNS disorders hemiplegic migraine and alternating hemiplegia of childhood, but muscle dysfunction has not been reported. Electrophysiological measurements of mutant pump activity in Xenopus oocytes revealed lower turnover rates in physiological extracellular K+ and an anomalous inward leak current in hypokalaemic conditions, predicted to lead to muscle depolarization. Our data provide important evidence supporting a leak current as the major pathomechanism underlying hypokalaemic periodic paralysis and indicate ATP1A2 as a new hypokalaemic periodic paralysis gene.

Episodic weakness and vacuolar myopathy in hypokalemic periodic paralysis.

We report a 50-year-old woman who presented with a 20 year history of gradually progressive lower extremity weakness, characterized by knee buckling with occasional falls and foot dragging. She also experienced difficulty in lifting her arms above her shoulders. The primary periodic paralyses are rare disorders caused by dysfunctional ion channels in skeletal muscle. The hypokalemic type is generally an autosomal dominant condition, due to missense mutations in the alpha subunits of the skeletal muscle L-type calcium channel genes, CACN1AS, or the skeletal muscle sodium channel gene, SCN4A. The affected patients typically present with episodic weakness. For our patient, the consumption of foods high in carbohydrates seemed to precipitate the episodes of weakness. Her family history was significant for six blood relatives, including three sons and three relatives on the paternal side, who had experienced similar symptoms. A biopsy of the left rectus femoralis muscle showed vacuolar myopathic changes in the scattered muscle fibers, accompanied by occasional degenerating and regenerating muscle fibers. There was no evidence of inflammation on the biopsy. The vacuoles were often associated with increased acid phosphatase staining. An electron microscopic examination showed that the vacuolar changes were due to T-tubule dilation, a characteristic of hypokalemic periodic paralysis. Other metabolic etiologies of vacuolar myopathy, such as acid phosphatase (lysosomal) associated acid maltase deficiency (a glycogen storage disease), need to be considered in the differential diagnosis.

Gitelman's syndrome presenting with hypocalcaemia, basal ganglia calcification and periodic paralysis.

Gitelman's syndrome (GS), also referred to as familial hypokalaemia-hypomagnesaemia syndrome, is an autosomal recessive renal tubular disorder characterised by hypokalaemic metabolic alkalosis, hypomagnesaemia and hypocalciuria. It is caused by a defect of the thiazide-sensitive sodium chloride co-transporter at the distal tubule. This condition was previously confused with Bartter syndrome. Documentation of hypocalciuria helps to differentiate GS from Bartter syndrome. We report a 44-year-old woman who presented with a history of seizure disorder and periodic paralysis. On investigation, she was found to have hypokalaemic metabolic alkalosis, hypomagnesaemia, hypocalciuria, hypoparathyroidism, hypocalcaemia and basal ganglia calcification, consistent with GS. The atypical features in our case, namely basal ganglia calcification and hypocalcaemia, prompted the writing of this case report.

Surgical treatment for thyrotoxic hypokalemic periodic paralysis: case report.

Thyrotoxic hypokalemic periodic paralysis (THPP) is a rare, potentially life-threatening endocrine emergency. It is characterized by recurrent muscle weakness and hypokalemia. Because many THPP patients do not have obvious symptoms and signs of hyperthyroidism, misdiagnosis may occur. The published studies revealed that definitive therapy for THPP is control of hyperthyroidism by medical therapy, radioactive iodine or surgery, but the long-term post-operative follow-up result was not observed. We reported two cases of medically refractory THPP with recurrent paralysis of extremities and hypokalemia, and both were combined with thyroid nodules. Both patients were treated with total thyroidectomy; the pathology revealed that one is Graves' disease with thyroid papillary carcinoma, and the other is adenomatous goiter with papillary hyperplasia. No episode of periodic paralysis was noted and laboratory evaluation revealed normal potassium level during the post-operative follow up. Our experience suggests that total thyroidectomy by experienced surgeon is an appropriate and definite treatment for medically refractory THPP, especially in cases combined with thyroid nodules.

3 Tesla sodium inversion recovery magnetic resonance imaging allows for improved visualization of intracellular sodium content changes in muscular channelopathies.

OBJECTIVES: To implement different sodium (²³Na)-magnetic resonance imaging (MRI) contrasts at 3 Tesla and to evaluate if a weighting toward intracellular sodium can be achieved, using 2 rare muscular channelopathies as model diseases. MATERIALS AND METHODS: Both lower legs of 6 patients with hypokalemic periodic paralysis (HypoPP), 5 patients with paramyotonia congenita (PC), and 5 healthy volunteers were examined on a 3 Tesla system with 3 different ²³Na-MRI pulse sequences. HypoPP and PC are rare muscle diseases, which are well characterized by elevated myoplasmic sodium at rest and after cooling, respectively. Intra- and interindividual comparisons were performed before and after provocation of one lower leg muscle. Three different ²³Na-MRI sequences were applied: (i) The total tissue sodium concentration was measured using a spin-density sequence (²³Na-TSC). (ii) A T1-contrast was applied to assess whether the known changes of the intracellular sodium concentration can be visualized by T1-weighting (²³Na-T1). (iii) An inversion recovery (²³Na-IR) sequence was used to utmost suppress the sodium signal from extracellular or vasogenic edema. Furthermore, a potential influence of the temperature dependency of the sodium relaxation times was considered. Additionally, H-MRI was performed to examine potential lipomatous or edematous changes. RESULTS: In HypoPP, all Na sequences showed significantly (P<0.05) higher signal intensities compared with PC patients and healthy subjects. In muscles of PC patients, provocation induced a significant (P=0.0007) increase (>20%) in the muscular ²³Na-IR signal and a corresponding decrease of muscle strength. Additionally, a tendency to higher ²³Na-T1 (P=0.07) and ²³Na-TSC (P=0.07) signal intensities was observed. Provocation revealed no significant changes in ¹H-MRI. In volunteers and in the contralateral, not cooled lower leg, there were no significant signal intensity changes after provocation. Furthermore, the ²³Na-IR sequence allows for a suppression of signal emanating from intravascular sodium and vasogenic edema. CONCLUSIONS: Our results indicate that the ²³Na-IR sequence allows for a weighting toward intracellular sodium. The combined application of the ²³Na-TSC and the ²³Na-IR sequence enables an improved analysis of pathophysiological changes that occur in muscles of patients with muscular channelopathies.

Insulin resistance in subjects with a history of thyrotoxic periodic paralysis (TPP).

BACKGROUND: Hyperinsulinaemia has been suggested as an important factor for developing hypokalaemic paralysis in patients with thyrotoxic periodic paralysis (TPP). Since hyperinsulinaemia is a common feature of insulin resistance, there may be a causal relationship between insulin resistance and TPP. OBJECTIVE: To compare insulin sensitivity between subjects with a history of TPP and others with a history of thyrotoxicosis without periodic paralysis. METHODS: Insulin sensitivity measured by euglycaemic hyperinsulinaemic clamp and 75-g oral glucose tolerance test (OGTT) were performed nonselectively in 10 subjects with a history of TPP (TPP group) and 10 age- and sex-matched subjects with a history of simple thyrotoxicosis (control group). All participants had euthyroidism and fasting plasma glucose of < 5.55 mmol/l at the time of the study. RESULTS: Body mass index and waist circumference of the TPP group were higher than that of the control group. One of 10 (10%) subjects in the TPP group and 6 of 10 (60%) in the control group had BMI of < 23 kg/m2. Areas under the curve (AUC) of plasma glucose after OGTT were comparable, while the AUC of serum insulin of the TPP group was higher than in the control group. The TPP group had lower insulin sensitivity than the control group. CONCLUSION: The subjects with a history of TPP were more obese and had lower insulin sensitivity than those with a history of simple thyrotoxicosis. Insulin resistance with compensatory hyperinsulinaemia may be a key feature of the pathogenesis of TPP.

Hypokalemic periodic paralysis in a patient with acquired growth hormone deficiency.

CONTEXT: Hypokalemic periodic paralysis (HypoPP) is a rare disorder consisting of sudden episodes of muscle weakness with areflexia involving all four limbs, which spontaneously resolve within several hours or days. Primary HypoPP is genetically determined, while secondary acquired HypoPP has been described in association with thyreotoxycosis, hyperaldosteronism, kidney diseases, diuretics and liquorice abuse, gastrointestinal potassium loss, or cysplatinum therapy. OBJECTIVE: To report a case of HypoPP associated with GH deficiency. PATIENT: A 33 yr-old man with hypopituitarism and diabetes insipidus secondary to pituitary stalk-localized sarcoidosis, and documented HypoPP episodes. CLINICAL PRESENTATION: Neurologic exam outside HypoPP episodes was normal. Needle electromyography was normal without myotonia or other spontaneous electric activity. Muscle biopsy documented a vacuolar myopathy with tubular aggregates. However, genetic analysis ruled out common mutations of the voltage-gated calcium channel observed in primary HypoPP. Common causes of secondary HypoPP were also ruled out. The patient was diagnosed with severe GH deficiency with modest fasting hyperinsulinemia and insulin resistance and started on GH replacement therapy, an alpha-glucosidase inhibitor (acarbose) and a diet low in simple carbohydrates. CONCLUSIONS: GH replacement therapy, acarbose and a diet low in simple carbohydrates resulted in the complete long-term (>2 yr) remission of HypoPP episodes. This is consistent with the hypothesis that the hyperinsulinemia associated to GH deficiency may trigger HypoPP episodes by increasing Na+/K+ ATPase activity and K+ transport into the intracellular compartment with subsequent hypokalemia.

[Symptomatic periodic paralysis secondary to primary Sjogren's syndrome]. / Paralysie périodique symptomatique d'un syndrome de Gougerot-Sjögren primitif.

INTRODUCTION: Hypokalaemic periodic paralysis can be primitive or secondary to potassium deficiency which can arise from several causes. Primary Sjogren's syndrome is a rare cause related to kidney involvement. CASE REPORT: A 50-year-old woman has been admitted for hypotonic tetraparesis which had appeared a few days earlier. History taking revealed three previous similar episodes with a notion of oral and lacrimal dryness. Laboratory tests revealed severe hypokalaemia, hyperchloremia, alkaline urinary pH and a minima 24h proteinuria. Additional investigations led to the diagnosis of a primary Sjogren's syndrome defined on the basis of international criteria. Kidney biopsy revealed tubular-interstitial nephritis. Oral corticosteroïd therapy and potassium supplementation led to symptom improvement. A recurrent episode also responded to treatment. Additional urinary alkalinisation has prevented further relapse. DISCUSSION: Primary Sjogren's syndrome is an exocrine disease causing systemic disorders. Tubular-interstitial nephropathy may occur in 25 percent of patients leading to distal tubular acidosis defined by the association of hypokalaemia, hyperchloremia and alkaline urinary pH. When hypokalaemia is severe, periodic paralysis may occur. CONCLUSION: Primary Sjogren's syndrome can lead to nephropathy and subsequent hypokalaemic periodic paralysis. Urinary alkalinisation is essential to prevent this catastrophic presentation from recurring.

An unusual cause of hypokalemic paralysis: aristolochic acid nephropathy with Fanconi syndrome.

Aristolochic acid nephropathy (AAN) with Fanconi syndrome presenting as hypokalemic paralysis is extraordinarily rare and may be unrecognized. We describe a 41-year-old man who presented with the inability to ambulate upon awakening in the morning. Physical examination revealed symmetric paralysis of bilateral lower limbs. Laboratory studies showed profound hypokalemia with renal potassium (K) wasting, hyperchloremic metabolic acidosis, hypophosphatemia with hyperphosphaturia, hypouricemia with hyperuricosuria, and glycosuria, consistent with Fanconi syndrome. Mild renal insufficiency was also observed. A meticulous search for underlying causes of Fanconi syndrome was unrevealing. However, a significant amount of aristolochic acid (AA) was detected in the consumed Chinese herb mixture (AA-I, 7 microg/g) for the treatment of his leg edema for the past 2 months. His hypokalemia, renal insufficiency, and Fanconi syndrome completely resolved 2 months after the withdrawal of Chinese herb mixture and the supplementation of potassium citrate and active vitamin D3. AAN with Fanconi syndrome should be considered as a cause of hypokalemia in any patient administered undefined Chinese herbs.

Cisplatin-induced hypokalemic paralysis.

INTRODUCTION: Profound hypokalemic conditions resulting from cisplatin therapy have been known to produce hypokalemic paralysis in rare cases. We describe such a case of cisplatin-induced hypokalemic paralysis. CASE SUMMARY: A 15-year-old Persian girl with ovarian dysgerminoma presented with severe generalized weakness and paraplegia 1 week after the fourth course of cisplatin-based chemotherapy. On physical examination, there was symmetric flaccid paralysis and areflexia in all of the extremities and particularly in the lower limbs. Her serum potassium concentration was 1.7 mmol/L. Metastatic disease was excluded by a comprehensive systemic evaluation. Complete clinical and paraclinical recovery was achieved after short-term administration of potassium supplement. DISCUSSION: Adverse drug reactions are common with cisplatin, but the drug is only rarely associated with hypokalemic paralysis. Based on the Naranjo causality algorithm, an objective assessment revealed cisplatin to be a probable cause of hypokalemic paralysis in this case. This adverse drug event--whether isolated or secondary to hypomagnesemia--may be deceptive, leading to a fatal mistake in the oncology setting, and should therefore be precisely differentiated from cancer-related complications. CONCLUSIONS: This case suggests that cisplatin should be added to the list of agents causing hypokalemic paralysis. Regular serum electrolyte measurement, the early detection of cation deficiency, and appropriate replacement of cations are all recommended.

Hypokalaemic periodic paralysis type 2 caused by mutations at codon 672 in the muscle sodium channel gene SCN4A.

Hypokalaemic periodic paralysis (hypoPP) is an autosomal dominant muscle disorder characterized by episodic attacks of muscle weakness associated with a decrease in blood potassium levels. Mutations in the gene encoding the skeletal muscle voltage-gated calcium channel alpha-1 subunit (CACNL1A3) account for the majority of cases. Recently, mutations in the gene coding for the skeletal muscle voltage-gated sodium channel alpha subunit (SCN4A) have been reported in a small number of hypoPP families. In order to determine the relative frequency of the CANCL1A3 and SCN4A mutations in a large population of hypoPP patients, and to specify the clinical and pathological features associated with each of them, we searched for mutations in 58 independent hypoPP index cases. We detected the causative mutation in 45 cases: 40 were linked to the CACNL1A3 gene and five to the SCN4A gene. One mutation has not been described before. Some remarkable clinical features were observed in a large hypoPP family carrying an SCN4A mutation: a complete penetrance in men and women, an early age at onset, postcritic myalgias and an increased number and severity of attacks induced by acetazolamide. A muscle biopsy, performed in two members of this family, revealed a peculiar myopathy characterized by tubular aggregates. In contrast, vacuoles were predominant in muscles from hypoPP patients carrying CACNL1A3 mutations. Our findings point to the usefulness of a molecular characterization of hypoPP patients in clinical practice. They also provide new clues for understanding the mechanisms behind functional and structural alterations of the skeletal muscle in hypoPP.