Association between Cytotoxic T-Lymphocyte-Associated Antigen 4 (CTLA-4) Locus and Early-Onset Anti-acetylcholine Receptor-Positive Myasthenia Gravis in Serbian Patients.

Genome-wide association studies (GWAS) have provided strong evidence that early- and late-onset MG have different genetic backgrounds. Recent in silico analysis based on GWAS results revealed rs231735 and rs231770 variants within CTLA-4 locus as possible MG causative genetic factors. We aimed to explore the association of rs231735 and rs231770 with MG in a representative cohort of Serbian patients. We conducted an age-, sex-, and ethnicity-matched case-control study. Using TaqMan allele discrimination assays, the frequency of rs231735 and rs231770 genetic variants was examined in 447 AChR-MG patients and 447 matched controls. There was no significant association of rs231735 and rs231770 with the entire MG cohort (P > 0.05). Nevertheless, when stratifying patients into early-onset (n = 183) and late-onset MG (n = 264), we found early-onset patients had a significantly lower frequency of the rs231735 allele T compared to controls (OR = 0.734, 95% CI = 0.575-0.938, p10e6 permutation < 0.05), and rs231735 genotype TT and rs231770 genotype TT had a protective effect on early-onset MG (OR = 0.548, 95% CI = 0.339-0.888, and OR = 0.563, 95% CI = 0.314-1.011, p10e6 permutation < 0.05). Consequently, we found that individuals with the rs231735-rs231770 haplotype GC had a higher risk for developing early-onset MG (OR = 1.360, P = 0.027, p10e6 permutation < 0.05). Our results suggest that CTLA-4 rs231735 and rs231770 may be risk factors only for patients with early-onset MG in Serbian population.

A misdiagnosed myasthenia gravis with anti-muscle-specific tyrosine kinase antibodies with possible childhood onset.

INTRODUCTION: Childhood onset myasthenia gravis associated with anti-muscle-specific tyrosine kinase antibodies is very rare and atypical in presentation. CASE REPORT: As a baby, the pre- sented patient was choking and sleeping with open eyes. She had weak cry and breathing difficulties. In childhood, there were fre- quent falls and fluctuating swallowing difficulties. At the age of 19 she was misdiagnosed with Miller Fisher syndrome due to the presence of diplopia, ataxia and hyporeflexia with spontaneous recovery. Repetitive nerve stimulation test was normal. Four years later, after several relapses, there was significant decrement on facial muscles. Neostigmine test was negative, provoking muscle fasciculations. Serum anti-muscle-specific tyrosine kinase antibodies were positive. With cyclosporine therapy she achieved the minimal manifestations status. CONCLUSION: The presented case confirms that childhood onset myasthenia gravis associated with anti-muscle-specific tyrosine kinase antibodies is often with atypical presentation and spontaneous remissions, so it could be easily misdiagnosed.

Diagnostic value of combined magnetic resonance imaging examination of brachial plexus and electrophysiological studies in multifocal motor neuropathy.

BACKGROUND/AIM: Multifocal motor neuropathy (MMN) is an immune-mediated disorder characterised by slowly progressive asymetrical weakness of limbs without sensory loss. The objective of this study was to investigate the involvement of brachial plexus using combined cervical magnetic stimulation and magnetic resonance imaging (MRI) of plexus brachialis in patients with MMN. We payed special attention to the nerve roots forming nerves inervating weak muscles, but without detectable conduction block (CB) using conventional nerve conduction studies. METHODS: Nine patients with proven MMN were included in the study. In all of them MRI of the cervical spine and brachial plexus was performed using a Siemens Avanto 1.5 T unit, applying T1 and turbo spin-echo T1 sequence, axial turbo spin-echo T2 sequence and a coronal fat-saturated turbo spin-echo T2 sequence. RESULTS: In all the patients severe asymmetric distal weakness of muscles inervated by radial, ulnar, median and peroneal nerves was observed and the most striking presentation was bilateral wrist and finger drop. Three of them had additional proximal weakness of muscles inervated by axillar and femoral nerves. The majority of the patients had slightly increased cerebrospinal fluid (CSF) protein content. Six of the patients had positive serum polyclonal IgM anti-GM1 antibodies. Electromyoneurography (EMG) showed neurogenic changes, the most severe in distal muscles inervated by radial nerves. All the patients had persistent partial CBs outside the usual sites of nerve compression in radial, ulnar, median and peroneal nerves. In three of the patients cervical magnetic stimulation suggested proximal CBs between cervical root emergence and Erb's point (prolonged motor root conduction time). In all the patients T2-weighted MRI revealed increased signal intensity in at least one cervical root, truncus or fasciculus of brachial plexus. CONCLUSION: We found clinical correlation between muscle weakness, prolonged motor root conduction time and MRI abnormalities of the brachial plexus, which was of the greatest importance in the nerves without CB inervating weak muscles.

[Disulfiram-induced polyneurophaty].

INTRODUCTION: Disulfiram is used in the treatment of chronic alcoholism, because of the unpleasant symptoms produced after ethanol intake. Although it is well tolerated in most patients, one in 15,000 patients will develop peripheral neuropathy every year, which is frequently misdiagnosed as alcoholic neuropathy. CASE REPORT: We report clinical, laboratory, electrophysiological and histopathological features in a 19-year-old patient who developed an acute distal sensorymotor neuropathy during the treatment of alcoholism. At the end of 4-month treatment with disulfiram 250 mg/day, the patient complained of weakness in distal segments of the lower limbs associated with burning dysesthesias, numbness and pain in the soles of the feet and the legs below the knees; reduction in foot strength, the absence of ankle jerk tendon reflexes, and tactile stocking pin-pick and vibratory sensory impairment in the lower limbs below the knee. Recovery was successful after treatment cessation. CONCLUSION: The significance of toxic neuropathy is shown by the fact that the recognition of clinical picture, identifying etiological factors and its elimination may prevent the evolution of polyneuropathy. This allows for more effective treatment of these neuropathies as apposite to idiopathic ones which can be treated only symptomatically. Our case report indicates the possibilities during a period with no serious damage to the axons manifested.

Immunoreactivity of glycoproteins isolated from human peripheral nerve and Campylobacter jejuni (O:19).

OBJECTIVE: Antibodies to ganglioside GM1 are associated with Guillain-Barré Syndrome (GBS) in patients with serologic evidence of a preceding infection with Campylobacter jejuni. Molecular mimicry between C. jejuni Lipopolysaccharide (LPS) and ganglioside GM1 has been proven to be the immunopathogenic mechanism of the disease in the axonal variant of GBS. GM1-positive sera cross-react with several Gal-GalNAc-bearing glycoproteins from the human peripheral nerve and C. jejuni (O:19). This study aimed to examine the immunoreactivity of the digested cross-reactive glycoproteins isolated from the human peripheral nerve and C. jejuni (O:19) with Peanut Agglutinin (PNA) as a marker for the Gal-GalNAc determinant, and with sera from patients with GBS. MATERIALS AND METHODS: For this purpose, the cross-reactive glycoproteins from peripheral nerve and C. jejuni (O:19) were enzymatically digested with trypsin and the obtained peptides were incubated with PNA and GBS sera. RESULTS: Western blot analysis of the separated peptides revealed several bands showing positive reactivity to PNA and to sera from patients with GBS, present in both digests from peripheral nerve and C. jejuni (O:19). CONCLUSIONS: These data indicate the possible molecular mimicry between the cross-reactive glycoproteins present in C. jejuni and human peripheral nerve and its potential role in the development of GBS following infection with C. jejuni (O:19).

Enteritis caused by Campylobacter jejuni followed by acute motor axonal neuropathy: a case report.

INTRODUCTION: Campylobacter species represent the main cause of bacterial diarrhea in developed countries and one of the most frequent causes of enterocolitis in developing ones. In some patients, Campylobacter jejuni infection of the gastrointestinal tract has been observed as an antecedent illness of acute motor axonal neuropathy, a variant of Guillain-Barré syndrome. CASE PRESENTATION: We present a case of acute motor axonal neuropathy following infection with Campylobacter jejuni subspecies jejuni, biotype II, heat stable serotype O:19. A 46-year-old Caucasian man developed acute motor neuropathy 10 days after mild intestinal infection. The proximal and distal muscle weakness of his upper and lower extremities was associated with serum antibodies to Campylobacter jejuni and antibodies to ganglioside GM1. The electromyographic signs of neuropathic muscle action potentials with almost normal nerve conduction velocities indicated axonal neuropathy. Our patient's clinical and electrophysiological features fulfilled criteria for the diagnosis of an acute motor axonal neuropathy, a subtype of Guillain-Barré syndrome. CONCLUSION: As this is the first case of acute motor axonal neuropathy following infection with Campylobacter jejuni subspecies jejuni reported from the Balkan area, the present findings indicate the need for systematic studies and further clinical, epidemiological and microbiological investigations on the prevalence of Campylobacter jejuni and its heat stable serotypes in the etiology of Guillain-Barré syndrome and other post-infectious sequelae.

Impairment of cardiac autonomic control in patients with amyotrophic lateral sclerosis.

The aim of this study was to investigate autonomic cardiac control in patients with amyotrophic lateral sclerosis (ALS). Fifty-five patients with sporadic ALS (28 female and 27 male; average age 56.00 +/- 10.34 years) were compared to 30 healthy controls (17 female and 13 male; average age 42.87 +/- 11.91 years). Patients with previous history of cardiac disease, diabetes mellitus, and impaired respiratory function were excluded from the study. Cardiovascular autonomic tests according to Ewing, power spectrum analysis of RR variability (low- and high-frequency bands - LF and HF, LF/HF index), real-time beat-to-beat ECG signal monitoring with heart rate variability analysis and baroreflex function analysis were carried out in all patients. Time-domain parameters of heart rate variability (mean RR interval, SDNN, SDANN, SDNN index, rMSSD and pNN50%) were obtained from 24-h ECG monitoring. ALS patients had a significantly higher score of sympathetic (p <0.01) and parasympathetic (p <0.001) dysfunction, as well as of the overall score of autonomic dysfunction (p <0.001). LF/HF index was significantly increased; baroreflex sensitivity and time-domain parameters of heart rate variability were highly significantly decreased in ALS patients (p <0.001). Our results demonstrated impaired cardiac autonomic control in ALS with marked parasympathetic dysfunction and sympathetic predominance.

[The effect of benfothiamine in the therapy of diabetic polyneuropathy].

INTRODUCTION: Diabetic polyneuropathy (DPN) is one of the most common diabetic complications, which can result in a significant functional impairment and reduction of the quality of life in affected individuals. It occurs due to alterations in different biochemical mechanisms which require the presence of thiamine, which is why this vitamin is used in the therapy of DPN. Due to the low bioavailability of the hydrosolubile forms of thiamine, its liposolubile preparations (benfotiamine) are preferentially used. OBJECTIVE: The aim of this study was to determine the efficacy of benfotiamine in combination with vitamin B6 in the therapy of DPN. METHODS: The study group comprised of 22 patients with DPN who were treated with the combination of benfotiamine and vitamin B6 during 45 days. The effect of the therapy was evaluated by the analysis of different clinical, laboratory and electrophysiological parameters before and after conducted treatment. RESULTS: After the treatment period, a statistically highly significant reduction of pain (p < 0.01) was noted with the reduction of pain score on visual analogue scale in 86.4% of patients. A significant reduction of subjective complaints was also noted, with decreased modified total symptom score in 95.5% of patients (p < 0.01). The presence of alodynia was reported at the beginning of the study in 77.3%, and after the benfotiamine therapy only in 22.7% of patients, while hyperpathy was initially present in 90.9%, and after treatment in 31.8% of patients (p < 0.01). Neurophysiological parameters of polyneuropathy also significantly improved, with the improvement of the compound muscle action potential amplitude in 68.2% ( p < 0.01) and motor conduction velocity of the peroneal nerve in 45.5% of patients (p < 0.01). The improvement of the sensory nerve action potential amplitude (p < 0.01) and sensory conduction velocity (p = 0.05) of the sural nerve was found in 45.5% of patients. After the treatment period, there was a highly statistically significant lowering of the glycosylated haemoglobin (p < 0.01), with improved findings in 63.6% of patients. After completed study treatment protocol 86.4% of patients rated their overall condition as improved. CONCLUSION: Our results showed that the conducted treatment resulted in significant subjective and objective improvement of the disease signs symptoms, which confirmed that benfotiamine was good starting choice for the treatment of diabetic polyneuropathy.

[Myasthenia gravis--a disease with variable impact on working capability].

Myasthenia gravis (MG) is a heterogeneous disease composed of several entities with disturbed neuromuscular transmission. The most frequent and clinically most important form of MG is an acquired autoimmune MG which includes more than 90% of all patients with failure of neuromuscular transmission. The main clinical feature of MG is changeable pathologic fatigability and weakness of one or more skeletal muscles and variable distribution of affected muscles. The disease is characterized by relapses and remissions. In 15% of patients the symptoms are limited to extraocular muscles causing variable ptosis, squint and double vision (Ocular MG). In remaining 85% of patients, during the first three years, the disease involves the majority of the head, neck and extremity skeletal muscles (Generalized MG). The clinical diagnosis may be sufficiently established by typical history, present or induced neurological signs of changeable muscle weakness and positive pharmacological tests. The assessment of the severity of the disease as well as the assessment of working capability is performed according to the classification recommended by Myasthenia Gravis Foundation of America (MGFA). The standardized score of the disease severity is based on testing function and strength of 9 groups of skeletal muscles. At the onset of the disease, regardless of the clinical form, the patient is incapable of work and subjected to hospitalization, clinical investigation and treatment. The efficacy of anticholinesterase drugs, thymectomy and/or immunosuppression determines the working capability and is recommended to be assessed six months after the initiation of treatment procedure.

Clinical case report atypical myopathy in a young girl with 91 CTG repeats in DM1 locus and a positive DM1 family history.

Myotonic dystrophy type 1 (DM1) is an autosomal dominant inheritable disease associated with an expansion of CTG repeats in the 3' UTR of the DMPK gene. The subject is an 11-year-old girl with atypical myopathy. Because the proband's family has a positive DM1 history, a molecular-genetic analysis for DM1 was performed. This study showed that proband had a small DMPK expansion (91 CTG repeats) although the observed myopathy would not normally be associated with DM1. These results show how the phenotypic manifestation of DM1 can have unusual symptoms with a completely unexpected relationship to genotype.

Epidemiology of myotonic dystrophy type 1 (Steinert disease) in Belgrade (Serbia).

The aim of this study was to estimate the incidence and prevalence of myotonic dystrophy type 1 (DM1) in Belgrade during the period 1983-2002. The patients who had DM1 were ascertained through hospital records from all neurological departments in Belgrade during 1983-2002. The molecular genetic analysis was performed in all patents included in the study. We identified 101 DM1 patients (52 males and 49 females). The average annual incidence rate of DM1 in Belgrade for the period observed was 2.0/1,000,000 (95% confidence interval (CI), 0.3-8.3), 2.1/1,000,000 (95% CI, 0.3-8.3) for males and 2.0/1,000,000 (95% CI, 0.3-8.3) for females. The highest age-specific DM1 incidence was registered in the age group 20-49: 3.4/1,000,000 (95% CI, 0.5-7.6), 4.0/1,000,000 (95% CI, 1.1-10.2) in males and 2.5/1,000,000 (95% CI, 0.5-7.6) in females. In the population of Belgrade, a cumulative probability of acquiring DM1 was 1 per 8621 for men and 1 per 9259 for women (1 per 8940 of the population for both sexes). The prevalence of DM1 in Belgrade on 31 December 2002 was 5.3/100,000 (95% CI, 4.2-6.6).

[High doses of immunoglobulin G in the therapy for severe forms of myasthenia gravis and Guillain-Barré syndrome].

BACKGROUND/AIM: High doses of immunoglobulin G (IVIG) have been recognized as a very important therapeutic modality in the treatment of neurological diseases. The aim of this report was to present our experience in the treatment of severe forms of myasthenia gravis (MG) and Guillain-Barré syndrome (GBS). METHODS: We analyzed the efficacy and safety of immunoglobulin G therapy in 53 patients with severe forms of myasthenia gravis, and 27 patients with very severe forms of Guillain-Barré syndrome. RESULTS: At the end of the follow-up period, a significant improvement was noticed in 47 out of 53 patients with myasthenia gravis (88.7%). In the group of 27 patients with severe forms of Guillain-Barré syndrome an improvement was registered in 19 patients (70.3%). The side effects of this therapy were mostly mild, manifested as headache, myalgia, skin rash, adynamia, and other clinically insignificant effects. No severe side effects were recognized. CONCLUSIONS: Our study clearly demonstrated the high efficacy of IVIG therapy in the treatment of severe forms of myastehnia gravis and Guillain-Barré syndome.

[Epidemiology of myasthenia gravis].

Myasthenia gravis (MG) is an organ-specific autoimmune disorder characterized by weakness and fatigue of voluntary muscles, and presence of autoantibodies to acetylcholine receptor of postsynaptic muscle membrane. A review of the international literature suggests that there is large variety of MG frequency and distribution. An annual incidence rate of MG is thought to be between 0.25 and 20 per 1,000,000 population. The prevalence of MG in world shows even wider variation, i.e. ranging from 50/1,000,000 in Hong Kong to 200/1,000,000 in Virginia (USA). Among population of Belgrade, an average annual incidence rate during the period 1983-1992 was 7.1/1,000,000, and prevalence on December 31, 1992 was 121.5/1,000,000. The mortality rate of MG is very low with value under 1/1,000,000. Epidemiological studies of MG have indicated trend of increasing MG prevalence with relatively stable incidence. This reflects the impact of effective treatment, improved diagnostic methods and prolonged survival. Due to development of intensive care facilities and immunomodulating treatment, the mortality of MG has significantly decreased. The most common age of MG onset is between 20 and 40 years. In this age group, about 60% of patients are women, while sex ratio at older age is 1:1. Stressful life events, viral infections, pregnancy and delivery may precipitate the development of MG. MG is associated with other autoimmune diseases in about 30% of cases. Although the number of patients with MG continues to rise, it is still a rare disease. Further epidemiological research with a view to establish population registries and to estimate economic impact of disease on population as well as quality of life of patients with MG is needed.

Diagnosis and Treatment of Chronic Immune-mediated Neuropathies.

The chronic autoimmune neuropathies are a diverse group of disorders, whose diagnosis and classification is based on the clinical presentations and results of ancillary tests. In chronic inflammatory demyelinating polyneuropathy, controlled therapeutic trials demonstrated efficacy for intravenous gamma-globulins, corticosteroids, and plasmaphereis. In multifocal motor neuropathy, intravenous gamma-globulins have been shown to be effective. In the other immune-mediated neuropathies, there are no reported controlled therapeutic trials, but efficacy has been reported for some treatments in non-controlled trials on case studies. Choice of therapy in individual cases is based on reported efficacy, as well as severity, progression, coexisting illness, predisposition to developing complications, and potential drug interactions.

Biotransformation of nitric oxide in the cerebrospinal fluid of amyotrophic lateral sclerosis patients.

Recent findings indicate that nitric oxide (NO*) over-production might be an important factor in the pathogenesis of sporadic amyotrophic lateral sclerosis (SALS). We measured significantly higher concentrations of uric acid and thiol group-containing molecules (R-SH groups) in the cerebrospinal fluid (CSF) from SALS patients compared to controls. The above factors, together with a slightly increased free iron concentration found in the CSF, favour conditions necessary for the formation of the dinitrosyl iron complex, capable of NO* bio-transformation. Thus, we performed ex vivo saturation of CSF (from both SALS patients and controls) with NO*. A decrease in the level of R-SH was found. This was more pronounced in the CSF from SALS patients. In the CSF from SALS patients the production of nitrite and hydroxylamine was greater than that observed in the CSF from controls. Moreover, we also found increased Cu,Zn-SOD activity in the CSF from SALS patients (when compared to control subjects) but no activity corresponding to Mn-SOD in any CSF samples. As Cu,Zn-SOD can react with nitroxyl forming NO*, the conditions for a closed, but continuous, loop of NO* biotransformation are present in the CSF of ALS patients.

[Antibodies to ganglioside GM1 and Campylobacter jejuni in patients with Guillain-Barré syndrome].

Guillain-Barré syndrome (GBS) is an acute immune mediated neuropathy, polyradiculoneuritis, characterized by rapid onset of symmetric extremity muscle paralysis, areflexia and albuminocytological dissociation in the cerebrospinal fluid (CSF). Recently, the heterogeneity of GBS has been noticed with definition of several GBS variants. The axonal GBS associated with anti-GM1 antibodies is the most important variant with the specific role of Campylobacterjejuni (CJ) in the induction of the disease. The role of our study was to determine the frequency of antecedent infection with CJ in the population of our patients with GBS, the association with anti-GM1 antibodies and the distribution of these antibodies within clinical forms of the disease. The diagnosis of GBS has been established in 17 patients according to clinical, electrophysiological and laboratory (CSF) criteria. The serum antibodies to 63 kDa flagellar protein isolated from CJ serotype 0:19 were determined by ELISA and Western blot and serum anti-GM1 antibodies by ELISA. In relation to the disability score two patients were ambulatory, five were ambulatory with support, seven were bedridden and two patients needed respirator. Five (29%) patients had pure motor, while 12 (71%) had sensorimotor GBS. The cranial nerves were involved in 11 (65%) and 9 (53%) patients had autonomic dysfunction. Electromyoneurography showed primary axonal, predominantly motor neuropathy in 6 (35%) and demyelinating sensorimotor neuropathy in 11 (65%) patients. The CSF protein content ranged from 0.47 to 3.88 g/L. The antecedent infection with CJ was shown by serum antibodies to CJ flagellar protein in 12 (71%) patients. Fifteen (88%) patients had IgG anti-GM1 antibodies. Twelve (71%) patients had both antibodies. In relation to the clinical form, anti-CJ antibodies were found in 8 (73%) out of 11 patients with demyelinating GBS and in 4 (66.6%) out of 6 patients with axonal GBS. The high titer of anti-GM1 antibodies was found in all patients (100%) with axonal and in 9 (82%) out of 11 patients with demyelinating GBS. The association of IgG anti-CJ and IgG anti-GM1 antibodies was found in 4 (66.6%) out of 6 patients with axonal and in 8 (73%) out of 11 patients with demyelinating GBS. The main features of our patients with GBS were high frequency of antecedent infection with CJ, unusually frequent association with anti-GM1 antibodies, and equally frequent association of anti-CJ and anti-GM1 antibodies in both, axonal and demyelinating GBS.

Proximal dystrophin gene deletions and protein alterations in becker muscular dystrophy.

Alterations in production of cytoskeletal protein dystrophin caused by in-frame gene mutations lead to the Becker muscular dystrophy. In this study we analyzed genotype-phenotype correlation in a group of Becker muscular dystrophy patients with deletions affecting the proximal part of dystrophin gene, encompassing exons 3-13. Four patients with deletions affecting N terminal dystrophin domain had early onset and faster progression of the disease, while three patients with deletions in the proximal part of dystrophin's rod domain had a more benign disease course. Our study suggests that proximal gene deletions in Becker muscular dystrophy have various phenotypic effects depending on the affected domain of protein dystrophin.

[Epidemiology of myotonic dystrophy type 1 in the population of central Serbia].

The objective of this epidemiological survey was to estimate the frequency and distribution of Myotonic dystrophy type 1 (MD1) (Steinert's disease) in central Serbia, during the period 1983-2002. The data on the number of diagnosed MD1 patients were obtained using the analysis of hospital records, which were examined in all the relevant neurological institutions in central Serbia in the mentioned period. Incidence rate and prevalence were used for the data analysis. In the study period in central Serbia, 154 patients (78 males and 76 females) with MD1 were identified. The average annual incidence rate of MD1 was 1.3 (95% CI-confidence interval 0.1-7.2) per 1,000,000 population, 1.4/1,000,000 (95% CI 0.1-7.2) for males, 1.3/1,000,000 (95% CI 0.1-7.2) for females. The trend of MD1 incidence rates in the observed period in central Serbia had a tendency of the statistically significant decrease, according to the linear model, in both male (y = 0.205 - 0.0066x, p = 0.021) and female populations (y = 0.1788 - 0.0048x, p = 0.032). The prevalence of MD1 on December 31, 2002 in central Serbia was 3.8/100,000 (95% IP 3.2-4.6), 3.7/100,000 (95% IP 3.3 - 4.8) for males, 3.3/100,000 (95% IP 3.0 - 4.4) for females.

Changes in thymopoiesis in myasthenia gravis.

This study was undertaken to investigate T-cell maturation in hyperplastic thymi of patients suffering from myasthenia gravis (MG). For this purpose, the expression of the major differentiational molecules (CD4, CD8, and CD3/TCRalphabeta) and that of the regulatory and activation molecules on thymocytes from MG patients and control subjects were estimated by flow cytometric analysis. In the MG patients the increase in relative proportion of immature (CD4-8- TCRalphabeta-) and the most mature (CD4+8- TCRalphabetahigh and CD4-8- TCRhigh encompassing immunoregulatory NKT) thymocytes followed by a decrease in that of CD4+8+CD3-/TCRalphabeta- cells was found. Furthermore, in these patients the relative proportion of CD4+HLA-DR+ and CD4+71+ cells was increased, whereas that of CD4+25+ cells was slightly, but significantly, decreased (reflecting, most likely, decreased contribution of T reg cells bearing this phenotype). Moreover, in MG thymi the percentage of CD45RA+ cells was reduced indicating changes in the selection processes. In keeping with this finding the reduced thymocyte apoptotic index and percentage of cells bearing apoptosing (CD4-8- TCRalphabetalow) phenotype were detected. In conclusion, the study demonstrates substantial changes in intrathymic differentiation of T cells in hyperplastic MG thymi and suggests alterations in selection events providing an increased escape of potentially autoreactive T-cell clones, on one side, and an altered maturation and/or selection of immunoregulatory cells (NKT and CD4+8-25+ T reg cells) keeping these cell clones under control, on the other side.