Efficacy of immunotherapy in seropositive and seronegative putative autoimmune autonomic ganglionopathy

[Autoimmune autonomic ganglionopathy and acute autonomic and sensory neuropathy]

Autonomic neuropathies may occur primarily or secondarily to various underlying diseases. Primary autonomic neuropathies are divided into pure autonomic neuropathy, autonomic neuropathy with sensory impairment, and autonomic neuropathy with sensory and motor impairment based on the concomitance or absence of sensory or motor dysfunctions. Autoimmune autonomic ganglionopathy refers to a pure autonomic neuropathy, which typically affects both cholinergic and adrenergic functions. About a half of the patients with autoimmune autonomic ganglionopathy are positive for anti-ganglionic acetylcholine receptor antibodies. The mode of progression widely ranges from acute to chronic, including that mimicking pure autonomic failure. The number of unmyelinated fibers in the sural nerve biopsy specimens tends to decrease with the duration of disease become longer. Immunomodulatory treatments are suggested to be effective for autoimmune autonomic ganglionopathy. Acute autonomic and sensory neuropathy is characterized by autonomic and sensory impairment without motor dysfunction that reaches its nadir within a short period of time mimicking the progression of Guillain-Barré syndrome. The monophasic clinical course and frequent presence of a history of antecedent infections suggests a participation of immune mechanisms. The initial symptoms are those related to autonomic disturbance or superficial sensory impairment, while deep sensory impairment accompanied by sensory ataxia subsequently appears in some patients. Sural nerve biopsy specimens reveal small-fiber predominant axonal loss, and autopsy cases show neuronal loss in the thoracic sympathetic and dorsal root ganglia. Hence, small neurons in the autonomic and sensory ganglia may be affected in the initial phase and, subsequently, large neurons in the sensory ganglia are damaged in acute autonomic and sensory neuropathy.

Gastrointestinal hypomotility with loss of enteric nicotinic acetylcholine receptors: active immunization model in mice

BACKGROUND

Autoimmune gastrointestinal dysmotility (AGID) is a limited form of dysautonomia. The only proven effector to date is IgG specific for ganglionic nicotinic-acetylcholine receptors containing α3 subunits [α3*- nicotinic acetylcholine receptor (nAChR)]. Rabbits immunized with recombinant α3-polypeptide produce α3*-nAChR autoantibodies, and profound AGID ensues. Human and rabbit α3*-nAChR-specific-IgGs induce transient hypomotility when injected into mice. Here, we describe success and problems encountered inducing gastrointestinal hypomotility in mice by active immunization.

METHODS

We repeatedly injected young adult mice of seven different strains susceptible to autoimmunity (spontaneous diabetes or neural antigen immunization-induced myasthenia gravis or encephalomyelitis) with: (i) α3-polypeptide, intradermally or (ii) live α3*-nAChR-expressing xenogeneic cells, intraperitoneally. We measured serum α3*-nAChR-IgG twice monthly, and terminally assessed blue dye gastrointestinal transit, total small intestinal α3*-nAChR content (radiochemically) and myenteric plexus neuron numbers (immunohistochemically, ileal-jejunal whole-mount preparations).

KEY RESULTS

Standard cutaneous inoculation with α3-polypeptide was minimally immunogenic, regardless of dose. Intraperitoneally injected live cells were potently immunogenic. Self-reactive α3*-nAChR-IgG was induced only by rodent immunogen; small intestinal transit slowing and enteric α3*-nAChR loss required high serum levels. Ganglionic neurons were not lost.

CONCLUSIONS & INFERENCES

Autoimmune gastrointestinal dysmotility is inducible in mice by active immunization. Accompanying enteric α3*-nAChR reduction without neuronal death is consistent with an IgG-mediated rather than T cell-mediated pathogenesis, as is improvement of symptoms in patients receiving antibody-depleting therapies.

A Unique Manifestation of Pupillary Fatigue in Autoimmune Autonomic Ganglionopathy

OBJECTIVE

To demonstrate a unique abnormality of the pupillary light reflex in patients with autoimmune autonomic ganglionopathy (AAG).

DESIGN

Case series.

SETTING

Autonomic clinics at 2 university hospitals (University of Texas Southwestern Medical Center and Beth Israel Deaconess Medical Center).

PARTICIPANTS

Seven patients with antibody-positive AAG.

INTERVENTIONS

All patients with AAG underwent either monocular or binocular infrared pupillometry using a standard 2-second light stimulus at a defined intensity. Findings were compared with those from healthy control subjects and patients with other autonomic disorders. The light stimulus used in this study was selected to eliminate the normal phenomenon of pupil escape.

MAIN OUTCOME MEASURES

The time to onset of redilation as well as other indices of pupillary constriction to light stimulus.

RESULTS

Patients with AAG exhibited premature pupillary redilation (mean [SD], 1.02[0.20] seconds) compared with healthy control subjects (mean [SD], 2.24 [0.10] seconds) and other patients with autonomic disorders (mean [SD], 2.30 [0.12] seconds) (P.001). In healthy control subjects and patients with other autonomic disorders, pupillary redilation always followed the termination of the light stimulus; in patients with AAG, redilation consistently occurred during the light stimulus. In 1 patient, serial repetitive light stimulation further decreased the time to onset of redilation.

CONCLUSIONS

Premature redilation of the pupil is a unique physiological feature seen only in patients with AAG. This phenomenon appears to be a manifestation of pupillary fatigue, a clinical correlate of defective synaptic transmission at the level of autonomic ganglia in antibody-positive AAG.

Treatment-responsive pandysautonomia in an adolescent with ganglionic α3-AChR antibodies

Autoimmune autonomic ganglionopathy (AAG) is a rare disorder that presents with pandysautonomia typically in middle age and elderly patients. AAG is typically associated with serum autoantibodies that bind to the alpha-3 subunit of the ganglionic acetylcholine receptor (α3-AChR Ab). We report a 13 year old girl who presented with gut pseudo-obstruction, bladder dysfunction and dilated pupils unresponsive to pilocarpine. She had positive α3-AChR Ab plus other autoantibodies suggesting an autoimmune diathesis. Our patient was initially resistant to steroid therapy but responded to the addition of azathioprine resulting in a near complete clinical remission. We conclude that pandysautonomia associated with α3-AChR Ab can occur in children and has multi-organ involvement.

The spectrum of clinicopathological features in pure autonomic neuropathy

We assessed the clinicopathological features of nine patients with pure autonomic neuropathy, that is, neuropathy without sensory or motor deficits. The duration from symptom onset to diagnosis ranged from 1 month to 13 years. Of eight patients in whom serum antiganglionic acetylcholine receptor antibody was determined, four were positive. All patients who tested positive for this antibody manifested widespread autonomic dysfunction, with the exception of one patient who only experienced orthostatic hypotension. However, patients who were negative for the antiganglionic acetylcholine receptor antibody presented with partial autonomic failure. One of these patients had diffuse parasympathetic failure and generalized hypohidrosis but no orthostatic hypotension, which is clinically compatible with postganglionic cholinergic dysautonomia. Electron microscopic examination revealed a variable degree of reduction in unmyelinated fibers. Compared with normal controls, the patients had a significantly increased density of collagen pockets (p < 0.05). Additionally, the percentage of Schwann cell subunits with axons (out of the total number of Schwann cell subunits associated with unmyelinated fibers) was significantly decreased (p < 0.01). The density of unmyelinated fibers tended to decrease with increasing time between the onset of autonomic symptoms and biopsy (p < 0.05). In conclusion, the clinical and pathological features of pure autonomic neuropathy vary in terms of progression, autonomic involvement, presence of the antiganglionic acetylcholine receptor antibody, and loss of unmyelinated fibers.

Sudomotor dysfunction in autoimmune autonomic ganglionopathy: a follow-up study

OBJECTIVE

We have previously shown that sudomotor dysfunction in autoimmune autonomic ganglionopathy is severe, widespread, and predominantly post-ganglionic. However, the long-term changes in sudomotor function have not been studied in detail. Our objective was to characterize the long-term changes in sudomotor dysfunction in patients with autoimmune autonomic ganglionopathy.

METHODS

Changes in sudomotor function were compared in a cohort of nine α3 nAChR antibody positive autoimmune autonomic ganglionopathy patients over an approximate 5-year period. Standard measurements of sudomotor function were used including the thermoregulatory sweat test and quantitative sudomotor axon reflex test.

RESULTS

Total body anhidrosis on thermoregulatory sweat testing showed improvement in four of nine patients. Quantitative sudomotor axon reflex testing for both forearm and foot sites was variable with four of nine patients showing improvement in total sweat output. Distribution of sudomotor dysfunction at follow-up was post-ganglionic in seven of nine patients at the foot site and three of nine patients at the forearm site. Overall, sudomotor dysfunction was post-ganglionic in seven of nine patients throughout the follow-up period (62.4 ± 19.4 months).

INTERPRETATION

Sudomotor dysfunction in autoimmune autonomic ganglionopathy was severe and widespread throughout the follow-up period for the majority of patients studied. Sudomotor dysfunction was predominantly post-ganglionic throughout the follow-up period.

Long-term treatment with rituximab of autoimmune autonomic ganglionopathy in a patient with lymphoma

OBJECTIVE

To report on the response to therapy in a patient with autoimmune autonomic ganglionopathy with a high titer of an autoantibody directed against the α-3 subunit of the nicotinic acetylcholine receptor (nAChR) of the autonomic ganglia.

DESIGN

Case report.

SETTING

University-based referral center for autonomic dysfunction.

PATIENT

Patient with prior indolent B-cell lymphoma who presented with symptomatic orthostatic hypotension and autonomic failure and was found to have a high titer of nAChR antibody.

INTERVENTION

Plasma exchange and rituximab therapy (both initial 4-week therapy and maintenance therapy).

MAIN OUTCOME MEASURES

Autonomic ganglionic antibody titer; the autonomic assessments were the presence of orthostatic hypotension, the concentration of plasma norepinephrine, and quantitative sweat testing.

RESULTS

Treatment with rituximab followed by plasma exchange significantly decreased the nAChR antibody titers for a short time, and then the titers increased. The titers suppressed to almost undetectable levels once regular maintenance therapy with rituximab was initiated. Reduction in nAChR antibody titer resulted in a decrease in orthostatic hypotension, an increased concentration of upright plasma norepinephrine, improvement in some sweat function, and improvement in symptoms.

CONCLUSIONS

Long-term rituximab therapy suppressed autoantibody production to undetectable levels over the course of 2 years and resulted in sustained clinical improvement in this patient with debilitating autoimmune autonomic ganglionopathy. More data are needed before rituximab therapy can be recommended as routine therapy for this disorder.

[Autoimmune autonomic ganglionopathy: a case series of six patients and literature review]

PURPOSE

Auto-immune autonomic ganglionopathy is a recently described clinical entity within the spectrum of autonomic neuropathies. Patients with auto-immune autonomic ganglionopathy typically present with rapid onset of severe autonomic failure. Acetylcholine receptor ganglionic antibodies, directed against ganglionic synapsis, disrupt synaptic transmission in autonomic ganglia and lead to autonomic failure. These antibodies are specific for auto-immune autonomic ganglionopathy and are present in 50% of patients.

METHODS

Descriptive retrospective study. We report six French patients who presented with auto-immune autonomic ganglionopathy diagnosed between 1996 and 2002.

RESULTS

Four patients were men and the median age at diagnosis was 45 years. All patients presented with a subacute autonomic failure with constant severe orthostatic hypotension. Serological testing of acetylcholine receptor ganglionic antibodies was performed in four out of the six patients and was found positive in three. All the patients received intravenous immunoglobulin and a clinical improvement was observed in four of them.

CONCLUSION

Auto-immune autonomic ganglionopathy is an unusual and overlooked disorder. However, this autonomic neuropathy deserves to be better known as most of the patients respond to immunomodulatory therapy.

Sudomotor dysfunction in autoimmune autonomic ganglionopathy

BACKGROUND

Autoimmune autonomic ganglionopathy is characterized by impairment of multiple autonomic domains of which sudomotor function is among the most common. Many patients with this disorder have difficulties with thermoregulation and anhidrosis. Our objective was to characterize the distribution and severity of sudomotor dysfunction in this disorder.

METHODS

Sudomotor function was analyzed in a cohort of 21 patients with ganglionic alpha3 nicotinic acetylcholine receptor (nAChR) antibody positive autoimmune autonomic ganglionopathy. Standard measurements of sudomotor function were used including the Thermoregulatory Sweat Test and Quantitative Sudomotor Axon Reflex Test.

RESULTS

The clinical presentation in all patients was characterized by widespread sudomotor dysfunction. Sudomotor impairment was predominantly postganglionic in 17 of the 21 patients studied. Higher ganglionic alpha3 nAChR antibody levels resulted in progressive postganglionic predominant dysfunction (postganglionic, r = 0.637, p = 0.002; mixed ganglionic, r = 0.709, p < 0.001). The pattern of anhidrosis on Thermoregulatory Sweat Testing was consistent with a ganglionopathy in the majority of patients (14 of 21) and a distal pattern in a minority of patients (8 of 21). These patterns of anhidrosis coupled with increasing postganglionic dysfunction in a proximal to distal pattern (foot > distal leg > proximal leg > forearm) indicate lesions at both the ganglia and distal axon of the postganglionic sudomotor sympathetic neuron.

CONCLUSIONS

Our data characterize the unique sudomotor dysfunction in autoimmune autonomic ganglionopathy as widespread, predominantly postganglionic, and a result of lesions at both the ganglia and distal axon. This study provides important support to the hypothesis that this disorder represents a ganglionic neuropathy.