RESUMO
Background: While the reported prevalence of polyneuropathies is 1%-3%, the incidence of hereditary transthyretin amyloidosis in the United States is estimated to be 1 in 100 000 individuals. Polyneuropathies are known to be difficult to treat and lead to significant morbidity. The aim of pain management is symptomatic treatment, with varying approaches to progression prevention being based on the causative pathophysiology.We assessed the prevalence of hereditary amyloid transthyretin variant (ATTRv) amyloidosis, a progressive autosomal dominant multisystem disease caused by the abnormal formation and extracellular deposition of transthyretin protein fibrils in various tissues, in an idiopathic polyneuropathy population by using genetic analysis. Methods: Individuals aged 18 and over with an established diagnosis of polyneuropathy, via electromyography testing that was deemed to be idiopathic, at a large, urban neurology clinic consented to an institutional review board-approved protocol for genetic testing. No further exclusions were made regarding age of onset, family history, axonal neuropathy subtype, comorbidities suggestive of ATTRv amyloidosis, etc. Clinical genetic testing was performed on 134 participants via an 81-gene panel associated with inherited neuromuscular disorders or targeted TTR gene sequencing with deletion and duplication analysis. Results: Within our cohort, 38.06% had at least one reportable finding in one of 38 distinct genes, for a total of 76 reported alterations. Four individuals were identified as having a single pathogenic alteration in an autosomal recessive gene, consistent with carrier status for the 4 following disorders: congenital insensitivity to pain with anhidrosis (NTRK1), Charcot-Marie-Tooth disease type IIP (LRSAM1), Brown-Vialetto-Van Laere syndrome type II (SLC52A2), hereditary sensory and autonomic neuropathy type III (IKBKAP). One individual was found to have a variant of uncertain significance (VUS) (p.G103D) in the TTR gene. Conclusion: Precision medicine on the molecular level with genetic testing in the identification of specific neuropathies may provide clinicians with more detailed information for developing a more direct therapeutic and treatment modality for better-targeted management. Further investigation is needed to expand on the knowledge and understanding of the clinical relevance surrounding the alterations found in the genetic evaluation of idiopathic neuropathy.
RESUMO
In response to a change in posture from supine or sitting to standing, autonomic reflexes normally maintain blood pressure (BP) by selective increases in arteriovenous resistance and by increased cardiac output, ensuring continued perfusion of the central nervous system. In neurogenic orthostatic hypotension (NOH), inadequate vasoconstriction and cardiac output cause BP to drop excessively, resulting in inadequate perfusion, with predictable symptoms such as dizziness, lightheadedness and falls. The condition may represent a central failure of baroreceptor signals to modulate cardiovascular function, a peripheral failure of norepinephrine release from cardiovascular sympathetic nerve endings, or both. Symptomatic patients may benefit from both non-pharmacologic and pharmacologic interventions. Among the latter, two pressor agents have been approved by the US Food and Drug Administration: the sympathomimetic prodrug midodrine, approved in 1996 for symptomatic orthostatic hypotension, and the norepinephrine prodrug droxidopa, approved in 2014, which is indicated for the treatment of symptomatic neurogenic orthostatic hypotension caused by primary autonomic failure (Parkinson's disease, multiple system atrophy and pure autonomic failure). A wide variety of off-label options also have been described (e.g. the synthetic mineralocorticoid fludrocortisone). Because pressor agents may promote supine hypertension, NOH management requires monitoring of supine BP and also lifestyle measures to minimize supine BP increases (e.g. head-of-bed elevation). However, NOH has been associated with cognitive impairment and increases a patient's risk of syncope and falls, with the potential for serious consequences. Hence, concerns about supine hypertension - for which the long-term prognosis in patients with NOH is yet to be established - must sometimes be balanced by the need to address a patient's immediate risks.