Transthyretin amyloidosis is a progressive and eventually fatal disease primarily characterized by sensory, motor, and autonomic neuropathy and/or cardiomyopathy. Given its phenotypic unpredictability and variability, transthyretin amyloidosis can be difficult to recognize and manage. Misdiagnosis is common, and patients may wait several years before accurate diagnosis, risking additional significant irreversible deterioration. This article aims to help physicians better understand transthyretin amyloidosis—and, specifically, familial amyloidotic polyneuropathy—so they can recognize and manage the disease more easily and discuss it with their patients. We provide guidance on making a definitive diagnosis, explain methods for disease staging and evaluation of disease progression, and discuss symptom mitigation and treatment strategies, including liver transplant and several pharmacotherapies that have shown promise in clinical trials.

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Diabetic neuropathy is the most common neuropathy in industrialized countries, and it is associated with a wide range of clinical manifestations. The vast majority of patients with clinical diabetic neuropathy have a distal symmetrical form of the disorder that progresses following a fiber-length-dependent pattern, with sensory and autonomic manifestations predominating. This pattern of neuropathy is associated with a progressive distal axonopathy. Patients experience pain, trophic changes in the feet, and autonomic disturbances. Occasionally, patients with diabetes can develop focal and multifocal neuropathies that include cranial nerve involvement and limb and truncal neuropathies. This neuropathic pattern tends to occur after 50 years of age, and mostly in patients with long-standing diabetes mellitus. Length-dependent diabetic polyneuropathy does not show any trend towards improvement, and either relentlessly progresses or remains relatively stable over a number of years. Conversely, the focal diabetic neuropathies, which are often associated with inflammatory vasculopathy on nerve biopsies, remain self-limited, sometimes after a relapsing course.

Non-systemic vasculitic neuropathy (NSVN) is routinely considered in the differential diagnosis of progressive axonal neuropathies, especially those with asymmetric or multifocal features. Diagnostic criteria for vasculitic neuropathy, classification criteria for NSVN, and therapeutic approaches to NSVN are not standardized. The aim of this guideline was to derive recommendations on the classification, diagnosis, investigation, and treatment of NSVN based on the available evidence and, where evidence was not available, expert consensus. Experts on vasculitis, vasculitic neuropathy, and methodology systematically reviewed the literature for articles addressing diagnostic issues concerning vasculitic neuropathy and NSVN as well as treatment of NSVN and the small-to-medium vessel primary systemic vasculitides using MEDLINE, EMBASE, and the Cochrane Library. The selected articles were analyzed and classified. The group initially reached consensus on a classification of vasculitides associated with neuropathy. Non-diabetic radiculoplexus neuropathy was incorporated within NSVN. The consensus definition of pathologically definite vasculitic neuropathy required that vessel wall inflammation be accompanied by vascular damage. Diagnostic criteria for pathologically probable vasculitic neuropathy included five predictors of definite vasculitic neuropathy: vascular deposits of IgM, C3, or fibrinogen by direct immunofluorescence; hemosiderin deposits; asymmetric nerve fiber loss; prominent active axonal degeneration; and myofiber necrosis, regeneration, or infarcts in peroneus brevis muscle biopsy (Good Practice Points from class II/III evidence). A case definition of clinically probable vasculitic neuropathy in patients lacking biopsy proof incorporated clinical features typical of vasculitic neuropathy: sensory or sensory-motor involvement, asymmetric/multifocal pattern, lower-limb predominance, distal-predominance, pain, acute relapsing course, and non-demyelinating electrodiagnostic features (Good Practice Points from class II/III evidence). Proposed exclusionary criteria for NSVN--favoring the alternate diagnosis of systemic vasculitic neuropathy--were clinicopathologic evidence of other-organ involvement; anti-neutrophil cytoplasmic antibody (ANCAs); cryoglobulins; sedimentation rate ≥100 mm/h; and medical condition/drug predisposing to systemic vasculitis (Good Practice Points supported by class III evidence). Three class III studies on treatment of NSVN were identified, which were insufficient to permit a level C recommendation. Therefore, the group reviewed the literature on treatment of primary small-to-medium vessel systemic vasculitides prior to deriving Good Practice Points on treatment of NSVN. Principal treatment recommendations were: (1) corticosteroid (CS) monotherapy for at least 6 months is considered first-line; (2) combination therapy should be used for rapidly progressive NSVN and patients who progress on CS monotherapy; (3) immunosuppressive options include cyclophosphamide, azathioprine, and methotrex...

Axonal loss is the major long-term pejorative prognostic factor in CIDP.

Transthyretin familial amyloid polyneuropathies (TTR-FAPs) are autosomal dominant neuropathies of fatal outcome within 10 years after inaugural symptoms. Late diagnosis in patients who present as nonfamilial cases delays adequate management and genetic counseling. Clinical data of the 90 patients who presented as nonfamilial cases of the 300 patients of our cohort of patients with TTR-FAP were reviewed. They were 21 women and 69 men with a mean age at onset of 61 (extremes: 38 to 78 years) and 17 different mutations of the TTR gene including Val30Met (38 cases), Ser77Tyr (16 cases), Ile107Val (15 cases), and Ser77Phe (5 cases). Initial manifestations included mainly limb paresthesias (49 patients) or pain (17 patients). Walking difficulty and weakness (five patients) and cardiac or gastrointestinal manifestations (five patients), were less common at onset. Mean interval to diagnosis was 4 years (range 1 to 10 years); 18 cases were mistaken for chronic inflammatory demyelinating polyneuropathy, which was the most common diagnostic error. At referral a length-dependent sensory loss affected the lower limbs in 2, all four limbs in 20, and four limbs and anterior trunk in 77 patients. All sensations were affected in 60 patients (67%), while small fiber dysfunction predominated in the others. Severe dysautonomia affected 80 patients (90%), with postural hypotension in 52, gastrointestinal dysfunction in 50, impotence in 58 of 69 men, and sphincter disturbance in 31. Twelve patients required a cardiac pacemaker. Nerve biopsy was diagnostic in 54 of 65 patients and salivary gland biopsy in 20 of 30. Decreased nerve conduction velocity, increased CSF protein, negative biopsy findings, and false immunolabeling of amyloid deposits were the main causes of diagnostic errors. We conclude that DNA testing, which is the most reliable test for TTR-FAP, should be performed in patients with a progressive length-dependent small fiber polyneuropathy of unknown origin, especially when associated with autonomic dysfunction.

Background: Few direct head-to-head comparisons have been conducted between drugs for the treatment of diabetic peripheral neuropathic pain (DPNP). Approved or recommended drugs in this indication include duloxetine (DLX), pregabalin (PGB), gabapentin (GBP) and amitriptyline (AMT). We conducted an indirect meta-analysis to compare the efficacy and tolerability of DLX with PGB and GBP in DPNP, using placebo as a common comparator.

Besides distal symmetrical sensory polyneuropathy (DSSP), middle-aged diabetic patients may present with focal or multifocal neuropathies, including proximal neuropathy of the lower limbs, the pathophysiological features of which are uncertain. We studied 10 non-insulin-dependent diabetic patients, 45 to 72 years of age, who developed a painful proximal neuropathy of the lower limbs for which other causes of neuropathy were carefully excluded. The proximal neuropathy was asymmetrical in all patients, sensory in 4, motor and sensory in the others. Signs of DSSP were present in all. A sample of the intermediate cutaneous nerve of the thigh, a sensory branch of the femoral nerve, was taken by biopsy and examined by light and electron microscopy. Examination of the nerve specimens revealed ischemic nerve lesions in 3 patients. Nerve ischemia was associated with vasculitis and inflammatory infiltration in 2 of them. In the other patients the lesions of the cutaneous nerve of the thigh included a varying incidence of axonal and demyelinative lesions similar to those observed in DSSP, with mild inflammatory infiltration in 4 of them. The density of myelinated and of unmyelinated was variably decreased. This study shows that axonal and demyelinative lesions similar to those found in diabetic DSSP are present in proximal nerves in mild forms of proximal diabetic neuropathy; while nerve ischemia, inflammatory infiltration, and vasculitis are encountered in the most severe forms of proximal diabetic neuropathy.