Familial dysautonomia

Familial dysautonomia (FD) is a neurodevelopmental genetic disorder within the larger classification of hereditary sensory and autonomic neuropathies, each caused by a different genetic error. The FD gene has been identified as IKBKAP. Mutations result in tissue-specific expression of mutant IkappaB kinase-associated protein (IKAP). The genetic error probably affects development, as well as maintenance, of neurons because there is neuropathological and clinical progression. Pathological alterations consist of decreased unmyelinated and small-fiber neurons. Clinical features reflect widespread involvement of sensory and autonomic neurons. Sensory loss includes impaired pain and temperature appreciation. Autonomic features include dysphagia, vomiting crises, blood pressure lability, and sudomotor dysfunction. Central dysfunction includes emotional lability and ataxia. With supportive treatment, prognosis has improved greatly. About 40% of patients are over age 20 years. The cause of death is usually pulmonary failure, unexplained sudden deaths, or renal failure. With the discovery of the genetic defect, definitive treatments are anticipated.     

A world without pain or tears*

Abstract The world of the child with familial dysautonomia (FD), a genetic disorder affecting development of the sensory and autonomic nervous system, is not idyllic. However, over the last 35 years advances in supportive treatments have improved morbidity and mortality. Recent genetic breakthroughs have further expanded thinking about this disorder and suggested innovative approaches to modifying genetic expression. This article reviews the current supportive treatment modalities and their rationale, as well as the suggested new treatments that may alter the function and prognosis of an individual affected with FD. * Dr. Felicia Axelrod presented this review as the 4^th Streeten Lecture at the 16^th International Symposium on the Autonomic Nervous System, Las Cabos, Mexico, October 2005.     

Increased frequency of rhabdomyolysis in familial dysautonomia

Introduction:Familial dysautonomia (FD; OMIM # 223900) is an autosomal recessive disease with features of impaired pain and temperature perception and lack of functional muscle spindles. After 3 FD patients presented with rhabdomyolysis in a short time span, we aimed to determine the frequency of rhabdomyolysis is this population. Methods: This study was a retrospective chart review of 665 FD patients. Results: Eight patients had at least 1 episode of rhabdomyolysis. Two patients had 2 episodes. The average incidence of rhabdomyolysis in FD was 7.5 per 10,000 person‐years. By comparison, the average incidence with statins has been reported to be 0.44 per 10,000 person‐years. Mean maximum creatine kinase (CK) level was 32,714 ± 64,749 U/L. Three patients had hip magnetic resonance imaging showing gluteal hyperintensities. Conclusions: Patients with FD have an increased incidence of rhabdomyolysis. We hypothesize that this may result from a combination of absent functional muscle spindles and muscle mitochondrial abnormalities. Muscle Nerve, 2015     

Genetically determined neuropathies

There have been major advances in the understanding of the genetically determined neuropathies in recent years. The underlying genetic defects are now known for many of the demyelinating hereditary motor and sensory neuropathies, and linkage data are available for some of the axonal hereditary motor and sensory neuropathies. This has important implications for both diagnosis and genetic counselling in this group of conditions. The genetic defect in most cases of familial amyloid polyneuropathy is also now known. In the most common form of familial amyloid polyneuropathy (FAP), transthyretin-related FAP, liver transplantation has been established as the first definitive treatment for a hereditary neuropathy and should be considered especially in young adult patients. This review will concentrate on the advances in the molecular genetics of the hereditary motor and sensory neuropathies, the hereditary sensory and autonomic neuropathies and the familial amyloid polyneuropathies with particular emphasis on the difficulties in classifying the first group. Received: 29 July 1997 Accepted: 2 September 1997     

Electrolyte therapy for refractory seizures in familial dysautonomia

PURPOSE: Video-EEG in a family of three patients with slow development and familial dysautonomia demonstrated absence seizures associated with 3-Hz generalized spike-and-wave discharges. The seizures were refractory to antiepileptic drugs (AEDs). METHODS: Treatment was given with rice-based cereal electrolyte oral solution. RESULTS: Treatment induced seizure freedom and normalization of EEG in all three patients. Repeated video-EEG monitoring with discontinuation of AEDs and maintenance of the oral hydration therapy was associated with recurrence of epileptic activity. All three patients have remained seizure free (approximately 1 year) with a combination of topiramate and electrolytic therapy. CONCLUSIONS: Rice-based oral electrolyte hydration therapy may play a role in prevention and control of seizures in patients with familial dysautonomia.     

Valsalva maneuver suggests increased rigidity of cerebral resistance vessels in familial dysautonomia

In familial dysautonomia (FD), cerebral autoregulation (CA) must adjust cerebral blood flow to extreme and rapid fluctuations in systemic blood pressure. Compromised CA during systemic blood pressure (BP) fluctuations might contribute to central autonomic dysfunction in FD. To evaluate CA during rapid BP changes, we monitored heart rate (HR), radial artery BP and middle cerebral artery blood flow velocity (CBFV), using transcranial Doppler sonography, in eight FD patients and twelve age-matched controls in supine position at baseline and during a Valsalva maneuver (VM, 40 mmHg expiratory pressure for 15 seconds). The best of four VM recordings was analyzed. We calculated two autoregulation parameters. CA_II reflects BP related autoregulatory CBFV increase in late phase II of VM. CA_II = [(CBFV_{II late}-CBFV_{II early})/CBFV_{II early}]/[(BP_{II late}-BP_{II early})/BP_{II early}]. CA_IV reflects BP and HR related autoregulatory CBFV increase in phase IV of VM. CA_IV = (CBFV_IV/CBFV_I)/(BP_IV/BP_I)/(HR_IV/HR_I). Baseline systemic BP, but not CBFV, was higher in the patients than the controls. During VM, both groups had similar CBFV and BP values, but CAIV and especially CA_II were significantly lower in the patients than the controls. We have documented that FD patients maintain stable CBFV during rapid BP fluctuations associated with early and late phase II and phase IV of VM suggesting that small intracerebral vessels of FD patients are less responsive to rapid systemic blood pressure fluctuations. To compensate for decreased sympathetic vascular innervation, we propose that FD patients may alter the myogenic component of CA by vessel wall thickening resulting in increased rigidity of intracerebral resistance vessels. The resulting vasoconstriction would allow maintenance of normal baseline CBFV in spite of chronic recumbent hypertension. Received: 31 August 2001, Accepted: 24 April 2002 Correspondence to M. J. Hilz, M. D., Ph. D.     

Effect of physical countermaneuvers on orthostatic hypotension in familial dysautonomia

Familial dysautonomia (FD) patients frequently experience debilitating orthostatic hypotension. Since physical countermaneuvers can increase blood pressure (BP) in other groups of patients with orthostatic hypotension, we evaluated the effectiveness of countermaneuvers in FD patients. In 17 FD patients (26.4 ± 12.4 years, eight female), we monitored heart rate (HR), blood pressure (BP), cardiac output (CO), total peripheral resistance (TPR) and calf volume while supine, during standing and during application of four countermaneuvers: bending forward, squatting, leg crossing, and abdominal compression using an inflatable belt. Countermaneuvers were initiated after standing up,when systolic BP had fallen by 40mmHg or diastolic BP by 30mmHg or presyncope had occurred. During active standing, blood pressure and TPR decreased, calf volume increased but CO remained stable.Mean BP increased significantly during bending forward (by 20.0 (17 – 28.5) mmHg; P = 0.005) (median (25^th – 75^th quartile)), squatting (by 50.8 (33.5 – 56) mmHg; P = 0.002), and abdominal compression (by 5.8 (–1 – 34.7) mmHg; P = 0.04) – but not during leg–crossing. Squatting and abdominal compression also induced a significant increase in CO (by 18.1 (–1.3 – 47.9) % during squatting (P = 0.02) and by 7.6 (0.4 – 19.6) % during abdominal compression (P=0.014)). HR did not change significantly during the countermaneuvers. TPR increased significantly only during squatting (by 37.2 (11.8 – 48.2) %; P = 0.01). However, orthopedic problems or ataxia prevented several patients from performing some of the countermaneuvers. Additionally, many patients required assistance with the maneuvers. Squatting, bending forward and abdominal compression can improve orthostatic BP in FD patients, which is achieved mainly by an increased cardiac output. Squatting has the greatest effect on orthostatic blood pressure in FD patients. Suitability and effectiveness of a specific countermaneuver depends on the orthopedic or neurological complications of each FD patient and must be individually tested before a therapeutic recommendation can be given.     

Decreased density of ganglia and neurons in the myenteric plexus of familial dysautonomia patients

Background: Familial dysautonomia (FD) is a hereditary disease of the autonomic and sensory nervous system. A prominent manifestation of FD is gastrointestinal dyscoordination, which contributes to the morbidity and mortality in FD. Aim: As the myenteric plexus is an essential factor in gastrointestinal motility control, we compared its morphology in appendices of FD patients and controls. Methods: Appendices from FD patients (N=19) were obtained during surgery of fundoplication and gastrostomy; normal appendices (N=17) were obtained from patients suspected to suffer from acute appendicitis, in whom, however, the appendix was found to be normal. Specimens were stained histochemically for NADPH diaphorase (NADPH-d) and in a blinded manner examined under a light microscope for seven morphologic parameters: ganglionic density, neuronal density, ganglionic area, number of stained neurons per ganglion, nerve bundle width, ratio between nervous tissue area and total area, and neuronal area. Results: Ganglionic density was 10.13 per mm² in controls versus 5.01 per mm² in FD (p<0.05). Neuronal density was 70.12 per mm² in controls, compared with 22.09 per mm² in FD (p<0.01). The other parameters were not different between the two groups. Conclusion: Densities of myenteric ganglia and neurons of FD patients were significantly lower than in controls. This deficiency may contribute to the pathogenesis of FD gastroenteropathy.     

Calcineurin and synaptophysin in the human spinal cord of normal individuals and patients with familial dysautonomia

Summary This report concerns the immunohistochemical demonstration of two neuronal Ca²⁺-binding proteins, calcineurin and synaptophysin, in the spinal cord of normal controls and from patients with familial dysautonomia. In controls, calcineurin immunoreactivity was highly concentrated in small nerve cells and fibers of the substantia gelatinosa. Synaptophysin immunoreactivity was normally distributed throughout the spinal cord gray matter, being highly concentrated in the substantia gelatinosa, the dorsal nucleus of Clarke and the anterior horn. In patients with familial dysautonomia, no apparent changes in calcineurin immunoreactivity were found in the substantia gelatinosa. By contrast, there was a significant depletion of synaptophysin-positive axon terminals in the substantia gelatinosa and in the dorsal nucleus of Clarke of patients with familial dysautonomia.     

A new type of non-progressive sensory neuropathy in children with atypical dysautonomia

Summary Three cases of non-progressive, sensory neuropathy with dysautonomia are presented. Light and electron microscopy on whole sural nerve biopsies revealed an almost total lack of myelinated nerve fibres. The total fibre count was also reduced as was the total number of Schwann cell nuclei. No degenerative phenomena were seen within the nerve fibres. The aberrations are probably caused by a maldevelopment of the neural crest implying a stunted proliferation and growth of sensory and autonomous neurones as well as a reduced proliferation of Schwann cells. Since the morphology and clinical features differ from that in other cases of sensory neuropathy with dysautonomia the three present cases are considered to represent a new type of the disease.Supported by grants from Folke Bernadotte-fonden, Första maj blommans riksförbund, Norrbacka-Eugenia stiftelsen, and Svenska Livförsäkringsbolags fond för klinisk hereditär forskning     

Novel mutation in the replication focus targeting sequence domain of DNMT1 causes hereditary sensory and autonomic neuropathy IE

DNMT1, encoding DNA methyltransferase 1 (Dnmt1), is a critical enzyme which is mainly responsible for conversion of unmethylated DNA into hemimethylated DNA. To date, two phenotypes produced by DNMT1 mutations have been reported, including hereditary sensory and autonomic neuropathy (HSAN) type IE with mutations in exon 20, and autosomal dominant cerebellar ataxia, deafness, and narcolepsy caused by mutations in exon 21. We report a sporadic case in a Japanese patient with loss of pain and vibration sense, chronic osteomyelitis, autonomic system dysfunctions, hearing loss, and mild dementia, but without definite cerebellar ataxia. Electrophysiological studies revealed absent sensory nerve action potential with nearly normal motor nerve conduction studies. Brain magnetic resonance imaging revealed mild diffuse cerebral and cerebellar atrophy. Using a next‐generation sequencing system, 16 candidate genes were analyzed and a novel missense mutation, c.1706A>G (p.His569Arg), was identified in exon 21 of DNMT1. Our findings suggest that mutation in exon 21 of DNMT1 may also produce a HSAN phenotype. Because all reported mutations of DNMT1 are concentrated in exons 20 and 21, which encode the replication focus targeting sequence (RFTS) domain of Dnmt1, the RFTS domain could be a mutation hot spot.     

Humoral immunodeficiency in congenital insensitivity to pain with anhidrosis

Congenital insensitivity to pain with anhidrosis (CIPA) is an autosomal recessive disorder caused by mutations in the neurotrophic tyrosine receptor kinase 1 (NTRK1) gene, which encodes the receptor for nerve growth factor. We report the clinical course of a 7-year-old girl with CIPA and proven NTRK1 mutation. In addition to recurrent dislocation of the left hip joint and avascular necrosis of the left talus, the patient also presented with recurrent infections secondary to hypogammaglobulinemia, a feature not previously known to be associated with CIPA. The patient was treated with regular administration of intravenous immunoglobulins. Conservative treatment of the recurrent left hip dislocation by cast immobilization and bracing was implemented to stabilize the joint. The implication of the immune system of the reported patient broadens the clinical phenotype associated with NTRK1 mutations.     

遗传性感觉交感神经病Ⅰ型一家系的临床、电生理和病理改变

目的报道一个遗传性感觉交感神经病Ⅰ型（HSANⅠ）家系的临床、病理和电生理改变特点。方法先证者为28岁男性，出现双下肢痛觉缺失1年余，伴随双脚多发溃疡，先证者之母在30岁出现双足麻木和溃疡。对先证者的周围神经和自主神经进行电生理检查，对腓肠神经进行病理检查。结果先证者手部皮肤交感反应延长，在足部没有引出；感觉神经传导速度在上肢出现减慢，（右尺神经33m／s，左正中神经45m／s），在下肢无反应；运动神经传导速度在上肢正常或减慢，在下肢减慢或无反应。腓肠神经的有髓神经纤维完全脱失，无髓神经纤维出现严重脱失。结论我国存在HSANⅠ型家系，病理检查显示有髓神经纤维和无髓神经纤维均被严重累及。皮肤交感反应检查交感神经损害的程度有助于该病的诊断。     

Hereditary motor and sensory neuropathy-Lom (HMSNL) in a Spanish family: clinical, electrophysiological, pathological and genetic studies

The clinical, electrophysiological, pathological and genetic findings are described in the first Spanish family diagnosed with hereditary motor and sensory neuropathy type Lom (HMSNL) initially identified by Kalaydjeva et al. in 1996. The three affected patients belong to a non-consanguineous family with Gypsy background that were followed up over 10 years. Serial clinical and neurophysiological examinations and genetic analysis were undertaken in every patient. Sural nerve biopsy was performed in the oldest patient. The clinical features are similar to those previously described in HMSNL and all of them showed abnormal brain auditory evoked potentials. The oldest brother developed sensorineural deafness at the age of 20. Conduction velocities were unobtainable in all patients and nerves tested except for the median nerve in the youngest child in whom conduction was severely slowed. Neuropathological examination revealed a severely depleted nerve with very few surviving myelinated fibers which possessed thin myelin sheaths. Schwann cell processes were arranged in circular configurations without typical onion bulb configuration. Genetic analysis showed that the maternal chromosome inherited by all three affected siblings displayed a very unusual haplotype. Our patients show the characteristic clinical, electrophysiological and pathological findings described in HMSNL and represent the first reported Spanish family affected from the disease. The genetic findings in this family have contributed to refine the HMSNL critical linkage region.     

Novel NTRK1 mutations cause hereditary sensory and autonomic neuropathy type IV: demonstration of a founder mutation in the Turkish population

Hereditary sensory and autonomic neuropathy type IV (HSAN IV), or congenital insensitivity to pain with anhidrosis, is an autosomal recessive disorder characterized by insensitivity to noxious stimuli, anhidrosis from deinnervated sweat glands, and delayed mental and motor development. Mutations in the neurotrophic tyrosine kinase receptor type 1 (NTRK1), a receptor in the neurotrophin signaling pathway phosphorylated in response to nerve growth factor, are associated with this disorder. We identified six families from Northern Central Turkey with HSAN IV. We screened the NTRK1 gene for mutations in these families. Microsatellite and single nucleotide polymorphism (SNP) markers on the Affymetrix 250K chip platform were used to determine the haplotypes for three families harboring the same mutation. Screening for mutations in the NTRK1 gene demonstrated one novel frameshift mutation, two novel nonsense mutations, and three unrelated kindreds with the same splice-site mutation. Genotyping of the three families with the identical splice-site mutation revealed that they share the same haplotype. This report broadens the spectrum of mutations in NTRK1 that cause HSAN IV and demonstrates a founder mutation in the Turkish population. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Beyhan Tüysüz and Fatih Bayrakli contributed equally to this work.     

Clinico-pathophysiological features of acute autonomic and sensory neuropathy: A long-term follow-up study

We evaluated the clinicopathophysiological features of three patients with acute autonomic and sensory neuropathy (AASN) who were followed for over 3 years. Signs of an autonomic disturbance including vomiting, anhidrosis, urinary disturbances, orthostatic hypotension and reduced coefficient of variation of the R-R interval on electrocardiography gradually improved about 1 year after onset. However, all three exhibited severe generalized sensory impairment for all modalities with the development of persistent sensory ataxia. No sensory nerve action potentials could be elicited and no somatosensory evoked potentials could be obtained. Sural nerve biopsy revealed severe axonopathy. In two patients, a high-intensity area was observed in the posterior column of the spinal cord on T2*-weighted axial magnetic resonance images. The level of neuron-specific enolase in cerebrospinal fluid was markedly elevated in two patients, indicating spinal nerve root or sensory neuron damage. Motor nerve function was well preserved in all patients. Our findings suggests that the major lesion in patients with AASN, particularly those with a sensory deficit, is present in the dorsal root ganglion neurons, that is there is a ganglioneuronopathy.