Peripheral neuropathy associated with eosinophilia-myalgia syndrome

Chemical exposure-induced systemic fibrosing disorders: Novel insights into systemic sclerosis etiology and pathogenesis

Numerous drugs and chemical substances are capable of inducing exaggerated tissue fibrotic responses. The vast majority of these agents cause localized fibrotic tissue reactions or fibrosis confined to specific organs. Although much less frequent, chemically-induced systemic fibrotic disorders have been described, sometimes occurring as temporally confined outbreaks. These include the Toxic Oil Syndrome (TOS), the Eosinophilia-Myalgia Syndrome (EMS), and Nephrogenic Systemic Fibrosis (NSF). Although each of these disorders displays some unique characteristics, they all share crucial features with Systemic Sclerosis (SSc), the prototypic idiopathic systemic fibrotic disease, including vasculopathy, chronic inflammatory cell infiltration of affected tissues, and cutaneous and visceral tissue fibrosis. The study of the mechanisms and molecular alterations involved in the development of the chemically-induced systemic fibrotic disorders has provided valuable clues that may allow elucidation of SSc etiology and pathogenesis. Here, we review relevant aspects of the TOS, EMS, and NSF epidemic outbreaks of chemically-induced systemic fibrosing disorders that provide strong support to the hypothesis that SSc is caused by a toxic or biological agent that following its internalization by endothelial cells induces in genetically predisposed individuals a series of molecular alterations that result in the development of SSc clinical and pathological alterations.

Pediatric sciatic neuropathy presenting as painful leg: A case report and review of literature

Introduction:

Mononeuropathies, in general, are very uncommon in childhood. Sciatic neuropathy (SN) is probably underappreciated in childhood and likely to represent nearly one quarter of childhood mononeuropathies.

Materials and Methods:

We present a 7-year-old girl who presented with painful right lower limb and abnormal gait. Detailed investigation revealed transient eosinophilia, abnormal neurophysiology, and magnetic resonance imaging (MRI) suggestive of isolated sciatic neuropathy.

Results:

She has responded very well to physiotherapy and has made a complete motor recovery, although she is left with an area of abnormal sensation affecting the lateral border of her right leg and the dorsum of her foot.

Discussion:

Differential diagnoses for pediatric SN have been discussed including compressive neuropathies in children and various hyper-eosinophilia syndromes. Compressive neuropathies in childhood are very rare and compression of the sciatic nerve is the second most common group after peroneal nerve lesion.

Toxic Myopathies

Muscle tissue is highly sensitive to drugs and toxins because ot its high metabolic activity and potential sites for disruption of energy-producing pathways. Early recognition of toxic myopathies is important, as they potentially are reversible on removal of the offending toxin, with greater likelihood of complete resolution the sooner this is achieved. Clinical features range from mild muscle pain and cramps to severe weakness with rhabdomyolysis, renal failure, and even death. The pathogenic bases can be multifactorial. This article reviews drugs responsible for common types of toxic myopathy and their clinical and histopathologic features and illustrates possible underlying cellular mechanisms.

Head and neck manifestations of eosinophilia-myalgia syndrome

Eosinophilia-myalgia syndrome (EMS) is a multisystemic disease that occurs in patients who have consumed products containing L-tryptophan. Prominent features include incapacitating myalgias, arthralgias, neuropathies, and eosinophilia. Despite the frequent association of dysphagia, dyspnea, and the potential for aspiration, the otolaryngology literature is devoid of information on EMS. In order to determine the frequency of otolaryngic symptoms, questionnaires were distributed to patients with EMS in 33 different US states. Among the 28 various head and neck manifestations studied, 70% of EMS patients complained of generalized muscle spasms, 66% xerostomia, 62% dyspnea, and 56% dysphagia. In addition, the epidemiology, clinical presentation, diagnostic criteria, and treatment options are discussed. This paper assesses the frequency of otolaryngic manifestations of EMS, as well as introduces this syndrome to the otolaryngologist-head and neck surgeon. It is important for the otolaryngologist to be aware of EMS and its manifestations and treatments so that patients with this potentially lethal disease can receive appropriate evaluation and expeditious treatment.

A murine model of the eosinophilia-myalgia syndrome induced by 1,1'-ethylidenebis (L-tryptophan)

The eosinophilia-myalgia syndrome (EMS) is a recently described disease that has been associated with the ingestion of L-tryptophan containing trace amounts of several impurities. The first such contaminant to be identified and linked epidemiologically to the EMS epidemic was 1,1'-ethylidenebis(L-tryptophan) (EBT), but its role in the etiology and pathogenesis of the syndrome has been controversial. We report the development of inflammation and fibrosis affecting the dermis and subcutis, including the fascia and perimyseal tissues, after the daily intraperitoneal administration of EBT to female C57BL/6 mice. Such changes are accompanied by increased numbers of mast cells, many of which appear to be degranulating. Plasma levels of quinolinic acid, a metabolic product of L-tryptophan via the kynurenine pathway, are reduced initially, and then become elevated when inflammation and fibrosis are more pronounced. The nature and location of the inflammatory cell infiltrate and fibrosis, as well as the presence of mast cells and alterations of L-tryptophan metabolism, are consistent with findings reported in patients with EMS. This murine model suggests that EBT may have been one of the mediators of EMS and should facilitate studies of the pathogenesis of EMS.

Axonal neuropathy in eosinophilia-myalgia syndrome

Three patients with eosinophilia-myalgia syndrome linked to consumption of L-tryptophan supplement developed a severe sensorimotor axonal neuropathy. All three had myalgia, elevated eosinophil count, and later developed fasciitis. Neuropathy was found at all stages of the illness and resulted in disability which was irreversible despite cessation of L-tryptophan. Nerve conduction studies showed reduced motor and sensory evoked response amplitudes with select sparing of some nerves and the arms were more involved than the legs. Cerebrospinal fluid protein content was increased in one of two patients so tested. Creatine kinase was normal and muscle biopsy showed perimysial inflammation. Sural nerve biopsy in one case showed epineural perivascular inflammation. Our data showed that a severe sensorimotor axonal neuropathy occurs in eosinophilia-myalgia syndrome, suggestive of mononeuritis multiplex.

L-tryptophan and the eosinophilia-myalgia syndrome: current understanding of the etiology and pathogenesis

The eosinophilia-myalgia syndrome (EMS) is a newly recognized illness that occurred in an epidemic form during the summer of 1989. The illness was characterized in the acute phase by myalgia and eosinophilia, followed in many patients by chronic cutaneous lesions, progressive neuropathy, and myopathy. EMS was associated with ingestion of L-tryptophan, an essential amino acid marketed as a nutritional supplement but widely used as a therapeutic agent. Evidence of abnormal L-tryptophan metabolism has been described in patients with EMS, and most likely reflects increased activity of indoleamine 2,3-dioxygenase, the rate-limiting enzyme of tryptophan metabolism. A contaminant identified in EMS-associated L-tryptophan preparations has been isolated and characterized, but its biologic effects and role as the etiologic agent in EMS remain to be established. Pathologic observations and experimental studies indicate that eosinophils, mononuclear inflammatory cells, and fibroblasts are potential effector cells, and interleukin-5 and transforming growth factor-beta are important mediators in the pathogenesis of the syndrome. Although few new cases of EMS occurred following the withdrawal of L-tryptophan, affected patients continue to manifest late sequelae of the disease, including dermal fibrotic conditions. This tragic outbreak of a newly recognized illness has focused interest on the role of chemical and environmental agents in the pathogenesis of various idiopathic illness characterized by tissue inflammation and fibrosis.

Tryptophan metabolism via the kynurenine pathway in patients with the eosinophilia-myalgia syndrome

OBJECTIVE

To investigate the metabolism of L-tryptophan (LT) via the kynurenine pathway in patients with the eosinophilia-myalgia syndrome (EMS).

METHODS

Measurement of LT, L-kynurenine, and quinolinic acid in plasma and cerebrospinal fluid (CSF) from subjects with EMS, from asymptomatic users of LT, and from normal subjects.

RESULTS

Plasma LT concentrations were lower in untreated EMS patients (n = 5) than in corticosteroid-treated EMS patients (n = 5; P less than 0.05) and in asymptomatic users of LT (n = 5; P less than 0.05). Untreated EMS patients, who had discontinued LT weeks to months prior to study, had significantly higher plasma levels of L-kynurenine and quinolinic acid than did corticosteroid-treated EMS patients (P less than 0.05), normal subjects (P less than 0.02), and asymptomatic users of LT (P less than 0.05). EMS patients also had significantly elevated levels of L-kynurenine (P less than 0.05) and quinolinic acid (P less than 0.001) in CSF compared with normal subjects. After a 1-gm oral dose of LT, untreated EMS patients (n = 4) showed lower peak levels of LT and accentuated synthesis of L-kynurenine and quinolinic acid, compared with these values in corticosteroid-treated EMS patients (n = 2), who responded like normal subjects (n = 5).

CONCLUSION

These data demonstrate that during the active phase of EMS, LT metabolism via the kynurenine pathway was accentuated, probably secondary to induction of the enzyme indoleamine-2,3-dioxygenase. Ingestion of large amounts of LT (median daily dose 1.5 gm) resulted in high concentrations of kynurenine-pathway metabolites in blood and extrahepatic tissues, which was accentuated in EMS patients and which may have played a significant role in the pathogenesis of the disease.

Demyelinating polyneuropathy in eosinophilia-myalgia syndrome

Eosinophilia-myalgia syndrome (EMS) is a newly recognized disorder, characterized by myalgia, weakness, scleroderma-like changes, and eosinophilia. EMS is associated with lots of L-tryptophan allegedly contaminated with byproducts of the manufacturing process. We describe 3 patients with EMS who presented with a severe demyelinating sensorimotor polyneuropathy. Electrodiagnostic studies revealed multifocal conduction block, slowing and temporal dispersion of motor responses, and prolonged or absent F-responses. Despite plasmapheresis; corticosteroids; and, in 1 patient, cyclophosphamide, 2 patients died and the remaining patient experienced minimal recovery. Pathology revealed patchy perivascular infiltrates and fibrosis in the connective tissue of muscle and nerve. Autopsy of the central nervous system in 2 patients did not reveal changes unique to EMS. In addition to other organ involvement, EMS may manifest as a potentially fatal polyneuropathy, which initially appears to have prominent demyelinating features.

Chronic demyelinating polyneuropathy associated with eosinophilia-myalgia syndrome

Eosinophilia-myalgia syndrome (EMS) is a newly described syndrome associated with use of L-tryptophan. A neuropathy with features of axonal degeneration has also been described in conjunction with EMS. Demyelinating polyneuropathy is not a well recognised association of the syndrome. The two patients with EMS reported presented with profound weakness and sensory loss and were found to have clinical, electrophysiological and pathological evidence of a chronic demyelinating polyneuropathy. The concurrence of this neuropathy with EMS, as well as several other features of their illness, is suggestive of an immune mediated mechanism in the pathophysiology of EMS.

Relationship of neurologic status in macaques infected with the simian immunodeficiency virus to cerebrospinal fluid quinolinic acid and kynurenic acid

Increased concentrations of the excitotoxin quinolinic acid (QUIN) have been implicated in the neurologic deficits and brain atrophy that may accompany infection with the human immunodeficiency virus type-1. Key neuropathologic features of the AIDS encephalitis are replicated in some macaques following infection with the simian immunodeficiency virus (SIV). In the present studies, cerebrospinal fluid (CSF) QUIN concentrations increased within 2 weeks following infection of 11 rhesus macaques (Macaca mulatta) with a neurotropic sooty mangabey isolate of the simian immunodeficiency virus (SIVsm) and were sustained to greater than 2 standard deviations above uninfected control macaques. Highest CSF QUIN concentrations (up to 400-fold above pre-inoculation levels) were observed in 6 SIVsm-infected macaques with motor and behavioral abnormalities during life, brain atrophy on MRI scan and inflammatory lesions within the brain and meninges. Four of the 6 neurologic macaques deteriorated rapidly within 12 weeks after inoculation and had substantially larger increases in CSF QUIN levels than 2 other neurologic macaques and 5 macaques without neurologic signs which survived for longer than 37 weeks. Increases in serum QUIN and CSF kynurenic acid also occurred but generally to a lesser degree than the increases in CSF QUIN. In some animals, increases in serum L-kynurenine concentrations and reductions in CSF and serum L-tryptophan occurred and were consistent with activation of indoleamine-2, 3-dioxygenase, the first enzyme of the kynurenine pathway in extrahepatic tissues. CSF QUIN exceeded serum QUIN in 8.8% of samples from macaques with neurologic signs, supporting increased QUIN synthesis within the central nervous system. Production of [13C6]QUIN was demonstrated in one SIVsm-infected macaque and one uninfected control macaque following an intracisternal injection of [13C6]L-tryptophan and suggests that L-tryptophan is a substrate for QUIN synthesis within the nervous system or meninges, although the cellular localization of QUIN synthesis remain to be determined. We conclude that increases in kynurenine pathway metabolism occur in SIV-infected macaques and are most prominent in macaques with neurologic signs. Macaques infected with SIV offer a model to investigate the relationship between the metabolism of neuroactive kynurenines and neurologic disturbances associated with retroviral infection.

Treatment of the eosinophilia-myalgia syndrome

The eosinophilia-myalgia syndrome (EMS) is a unique entity associated with products that contain L-tryptophan (L-trp). Studies of the underlying etiopathogenic processes are underway. EMS is a distinct syndrome, but shares features with eosinophilic fasciitis and other variants of systemic sclerosis. A wide spectrum of clinical manifestations has been described, but there is no consensus regarding treatment. We report the clinical and laboratory features of 12 patients. All were treated with nonsteroidal antiinflammatory drugs (NSAIDs) and analgesics with transient or minimal effect. Two received D-penicillamine (DP) and colchicine, with minimal improvement; one had no response to azathioprine (AZA). Eleven received corticosteroids and had improvement of general symptoms, arthralgias, arthritis, myalgias, skin changes, eosinophilia, and leukocytosis. Nevertheless, all but the latter two findings recurred when corticosteroids were tapered. Seven patients who were unresponsive to the former treatments received low-dose pulse oral methotrexate. Six exhibited continued improvement after a mean follow-up of 4.5 months, with good drug tolerance. Corticosteroids were tapered and, in some instances, discontinued without relapse or complications. One patient improved but later died of aspiration pneumonia. We conclude that methotrexate (MTX) is a therapeutic alternative for patients with severe or refractory EMS.

Simultaneous development of two cases of eosinophilia-myalgia syndrome with the same lot of L-tryptophan in Japan

A newly recognized and well-described connective tissue disease, eosinophilia-myalgia syndrome, is thought to relate to L-tryptophan ingestion. The suspect L-tryptophan made in Japan has been distributed in Japan and in the United States. Different from many case reports of eosinophilia-myalgia syndrome in the United States, it has not been reported in Japan. We describe the first case reports of two Japanese patients. Eosinophilia-myalgia syndrome developed in these patients simultaneously, during L-tryptophan treatment by the same physician using the same lot of prescribed L-tryptophan. Furthermore, both patients had the following HLA types: HLA-Aw33(w19), -B44(12), and -DR6. These findings implicate the existence of another factor in the development of eosinophilia-myalgia syndrome in addition to the suspect L-tryptophan.

Prevention and management of drug-induced peripheral neuropathy

When symptoms of peripheral neuropathy appear, the possibility that they have been induced by drugs should be considered. A large number of drugs of all kinds, several of which are considered indispensable, have been implicated in peripheral neuropathy. A list of some of these drugs is provided. Neuropathy is a universal and dose-limiting factor during treatment with vinca alkaloids, but is otherwise a rare complication of drug therapy. Drug-induced peripheral neuropathy is almost always due to a dose-dependent primary axonal degeneration caused either by toxic reactions or by metabolic changes in neurons or their surroundings. The use of drugs should be restricted, especially in patients with a risk for development of neuropathy or with already existing neuropathy, e.g. patients with hepatic or renal failure, diabetes mellitus, or malnutrition. Patients should be given vitamins, prophylactically or therapeutically, which will sometimes allow a treatment to be continued. In other cases of drug-induced neuropathy the drug should be stopped. Reversal depends on the severity of the neuropathy, intensity and duration of the treatment and existence of causative cofactors, but generally the prognosis is good. While waiting for recovery physiotherapy is of importance, and when paraesthesia and pain are troublesome the patient should be treated with carbamazepine, imipramine or lidocaine (lignocaine).