[High prevalence of subclinical thyroidal disease among individuals attended in health control]

BACKGROUND

There is no information about the prevalence of thyroidal diseases in the general Chilean population.

AIM

To assess the prevalence of thyroidal diseases in individuals attended in occupational health examinations.

SUBJECTS AND METHODS

Four hundred seventy two individuals were examined between 1998 and 1999. In all, serum levels of thyroid hormones, TSH and anti thyroidal antibodies (anti microsomal, anti thyroid peroxidase and anti thyroglobulin) were measured.

RESULTS

Forty four subjects were excluded from the study due to an incomplete medical record and 18 due to a personal history of thyroidal disease. Abnormal serum levels of thyroid hormones or TSH were detected in 28 subjects (6.8%). Four (1%) had hypothyroidism, 23 a subclinical hypothyroidism (5.6%) and one (0.2%) had hyperthyroidism. In 87 subjects (21.2%) at least one of the antibodies was positive. Positive anti thyroid antibodies were found in 14 of 28 subjects (50%) with abnormal thyroid hormone levels, compared with 73 of 382 subjects (19.1%) with normal thyroid hormone levels. Thyroid dysfunction was twice as frequent in women than in men.

CONCLUSIONS

In this sample, a 6.8% prevalence of abnormal thyroid function tests was detected.

[Excess of mineralocorticoids in essential hypertension: clinical-diagnostic approach]

BACKGROUND

Primary hyperaldosteronism is more frequent among subjects with essential hypertension than previously thought. The prevalence, according to local and international evidence could fluctuate between 9 and 10%.

AIM

To investigate if subjects with essential hypertension have different aldosterone and renin plasma levels than normotensive subjects.

PATIENTS AND METHODS

One hundred twenty five subjects with essential hypertension, not receiving medications for at least two weeks prior to the study and 168 age and sex matched normotensive controls were studied. Blood was drawn between 9 and 10 AM during a sodium free diet to determine plasma aldosterone, plasma renin activity and potassium.

RESULTS

Plasma aldosterone was higher in hypertensive subjects than controls (11.6 +/- 7.6 and 9.9 +/- 5.1 ng/dl respectively; p = 0.04). Plasma renin activity was lower in hypertensives than controls (1.42 +/- 1.28 and 1.88 +/- 1.39 ng/ml/b respectively; p < 0.001). Thus, plasma aldosterone/plasma renin activity ratio was higher in hypertensives (13.8 +/- 13.5 and 8.3 +/- 7.8; p < 0.001). A pathological ratio was defined as over 25, corresponding to the mean plus two standard deviations of the control group. Primary hyperaldosteronism was found in 5/125 hypertensives (4%) and 1/168 normotensive subject (0.6%). None had hypokalemia.

CONCLUSIONS

Subjects with essential hypertension have higher plasma aldosterone and lower plasma renin activity than normal controls. A plasma aldosterone/plasma renin activity over 25 was defined as abnormal.

Primary hyperaldosteronism in essential hypertensives: prevalence, biochemical profile, and molecular biology

There is evidence that primary aldosteronism (PA) may be common in patients with essential hypertension (EH) when determinations of serum aldosterone (SA), plasma renin activity (PRA), and the SA/PRA ratio are used as screening. An inherited form of primary hyperaldosteronism is the glucocorticoid-remediable aldosteronism (GRA) caused by an unequal crossing over between the CYP11B1 and CYP11B2 genes that results in a chimeric gene, which has aldosterone synthase activity regulated by ACTH. The aim of this study was to evaluate the prevalence of PA and the GRA in 305 EH patients and 205 normotensive controls. We measured SA (1-16 ng/dL) and PRA (1-2.5 ng/mL x h) and calculated the SA/PRA ratio in all patients. A SA/PRA ratio level greater than 25 was defined as being elevated. PA was diagnosed in the presence of high SA levels (>16 ng/dL), low PRA levels (<0.5 ng/mL x h), and very high SA/PRA ratio (>50). Probable PA was diagnosed when the SA/PRA ratio was more than 25 but the other criteria were not present. A Fludrocortisone test was done to confirm the diagnosis. GRA was differentiated from other forms of PA by: the aldosterone suppression test with dexamethasone, the high levels of 18-hydroxycortisol, and the genetic detection of the chimeric gene. In EH patients, 29 of 305 (9.5%) had PA, 13 of 29 met all the criteria for PA, and 16 of 29 were initially diagnosed as having a probable PA and confirmed by the fludrocortisone test. Plasma potassium was normal in all patients. The dexamethasone suppression test was positive for GRA in 10 of 29 and 18-hydroxycortisol levels were high in 2 of 29 patients who had also a chimeric gene. In normotensive subjects, 3 of 205 (1.46%) had PA, and 1 of 205 had a GRA. In summary, we found a high frequency of normokalemic PA in EH patients. A high proportion of PA suppressed SA with dexamethasone, but only a few had a chimeric gene or high levels of 18-hydroxycortisol. These results emphasize the need to further investigate EH patients.

Stimulated single fiber EMG of the frontalis muscle in the diagnosis of ocular myasthenia

We performed single fiber electromyography by axonal stimulation (SFEMG-AS) of the frontalis muscle of 16 patients with ocular myasthenia gravis (OM) and 33 controls. In the controls, values of mean consecutive differences (MCD) ranged from 5 to 55 micros (average, 14.7 +/- 2.8 micros) and mean MCD of individual MPs was 14. 6 +/- 6.8 micros. All the OM patients showed abnormal SFEMG-AS jitter before prostigmine was administered (mean MCD: 49.19 +/- 21. 82 micros, percentage of blocks: 20.97 +/- 18.53). Twenty or 30 min after prostigmine had been administered, we saw a significant improvement in jitter: mean MCD was 36.38 +/- 22.49 micros (P = 0. 005), and percentage of blocks was 10.16 +/- 18.87 (P = 0.008). The method was well tolerated. We conclude that SFEMG-AS of the frontalis muscle is a sensitive technique for the diagnosis of OM and is easy to carry out.

[Electrophysiological evaluation of level compression in elbow ulnar neuropathy]

OBJECTIVES

In order to establish the focal compression in the elbow, a study of 318 patients with clinical manifestations of ulnar neuropathy was carried out. We divided the patients in three groups: I) those who presented mechanical anomalies with background of fracture, elbow valgus...; II) those who did not present mechanical anomalies, but they have been in bed long time or they have been operated...; III) those who did not have evident cause for the compression.

MATERIAL AND METHOD

Antidromic sensory conduction and segmentary motor conduction of the ulnar nerve were studied, and segmental motor conduction along the elbow with interval of 2 centimetres (technique of Kanakamedala).

RESULTS

83.6% of the 318 ulnar neuropathy had the focal compression in the ulnar sulcus. 8.2% had the focal compression distal to the ulnar sulcus. 0.94% had double focal compression. In 7.2% was not possible to determinate the focal compression. In group I, the focal compression was in the ulnar sulcus in 93.8% of the cases. In group II, the focal compression was in the ulnar sulcus in 94.3% of the cases. In group III, the focal compression was in the ulnar sulcus in 55.8% of the cases, and distal to the ulnar sulcus in 29.1% of the cases.

CONCLUSION

It is possible to localize the focal compression of the ulnar neuropathy in the elbow, with high level of probability, with the nerve conductions. This allows the surgeon to be orientated about therapeutical attitude.

A(-6)G variant of angiotensinogen gene and aldosterone levels in hypertensives

Recently, a novel mutation in the promoter region of the angiotensinogen gene that involves the presence of an adenine instead of a guanine 6 bp upstream from the transcription initiation site (A(-6)G) has been shown to induce an increase in gene transcription. The aim of this study was to determine the prevalence of the A(-6)G mutation in essential hypertensive patients and to correlate it with aldosterone and renin activity levels. We studied 191 hypertensives. We measured levels of aldosterone (plasma and urinary) and plasma renin activity. We determined the variants A and G using a mutagenically separated polymerase chain reaction technique. In 191 hypertensives, the A variant was detected in 266 of 382 (69.6%) and the G variant in 116 of 382 alleles (30.4%). Plasma aldosterone was significantly higher in patients homozygous for AA than in those homozygous for GG (369+/-208 versus 246+/-142 pmol/L). Urinary aldosterone was significantly higher in homozygous AA than in AG or GG patients (62.4+/-39.4 versus 50.8+/-25.2 and 37.4+/-22.3 nmol/d, respectively). When the patients were grouped according to the presence or absence of the A allele, the aldosterone levels and the plasma aldosterone/plasma renin activity ratio were significantly higher in patients with the A allele. The presence of the A variant was associated with higher levels of aldosterone. These results suggest that the presence of the A variant could determine the appearance of arterial hypertension through higher transcription activity of the angiotensinogen gene and concomitant aldosterone production.

[High prevalence of undiagnosed primary hyperaldosteronism among patients with essential hypertension]

BACKGROUND

Classically, primary hyperaldosteronism was diagnosed in no more than 1% of patients with hypertension, when hypokalemia was used as the screening test. However, numerous patients with primary hyperaldosteronism do not have hypokalemia and the disease remains undiagnosed.

AIM

To assess the prevalence of normokalemic primary hyperaldosteronism among patients classified as having essential hypertension.

PATIENTS AND METHODS

One hundred hypertensive patients with a blood pressure over 145/95 were studied. Plasma aldosterone and plasma renin activity were measured in all. A primary hyperaldosteronism was diagnosed when high aldosterone levels (over 16 ng/dl) and low plasma renin activity (below 0.5 ng/ml/h) coexisted in two blood tests or the aldosterone/plasma renin activity ratio was over 50. A probable primary hyperaldosteronism was diagnosed when the ratio was between 25 and 50 and these patients were subjected to a Fludrocortisone test to confirm the diagnosis. A dexametasone suppression test was done to discard glucocorticoid remediable aldosteronism. An adrenal TAC scan was done to all patients with primary hyperaldosteronism.

RESULTS

A diagnosis of primary hyperaldosteronism was reached in ten patients. Seven had elevated aldosterone and low plasma renin activity. In three the diagnosis was confirmed with the fludrocortisone test. All ten patients had normal serum potassium levels. Dexametasone suppression test was positive in three patients, that normalized their blood pressure levels. Adrenal TAC scans showed an adenoma in one patient and hyperplasia in another.

CONCLUSIONS

Primary hyperaldosteronism is more frequent than previously thought, it is overlooked when hypokalemia is used as the screening test and it can only be diagnosed measuring plasma aldosterone and renin activity.

[Hypertension and mineralocorticoids. Usefulness of renin and aldosterone measurements]

Recently, some genetic forms of hypertension have been well characterized. These forms can be globally called mineralocorticoid hypertension and are due to different alterations of the renin-angiotensin-aldosterone system (SRAA). Among these, classic primary hyperaldosteronism and its glucocorticoid remediable variety, in which hypertension is secondary to aldosterone production, must be considered. There are also conditions in which mineralocorticoid activity does not depend on aldosterone production. These conditions generate a hyporeninemic hyperaldosteronism, observed in Liddle syndrome, apparent mineralocorticoid hypertension, 11- and 17-hydroxylase deficiency, among others. The detection of these forms of hypertension is only feasible if the renin-angiotensin-aldosterone system is assessed, measuring renin and aldosterone levels. This article reviews these forms of hypertension, their clinical workup and their relevance in the usual hypertensive patients.

[Pericarditis secondary to the rupture of a hydatid cyst]

Cardiac hydatic cysts are rare and represent 0.5 to 2% of all hydatic cysts in humans, but usually associated with fatal complications. We report a case of a male 27 years old with a hydatid cyst located in left ventricle asymptomatic until rupture. It was diagnosed by two-dimensional echocardiogram in a control.

[Neuropathy by n-hexanes: a generalized disorder of the intermediate filaments]

BACKGROUND

Chronic inhalation of glues containing n-hexanes produces neurofilament (NF) accumulation which induces sensory-motor polyneuropathy. In vitro assays have shown this toxic substance causes intermediate filaments (IF) aggregation in non-neuronal cells.

OBJECTIVE

To describe intermediate filament changes in human pathology due to n-hexanes.

PATIENTS AND METHODS

Sural nerve and skin biopsy samples from 2 patients who suffered from a severe sensory-motor polyneuropathy after prolonged inhalation of glue containing n-hexane were examined with electron microscopy and vimentin and phosphorylated NF immunocytochemistry.

RESULTS

Abnormal accumulations of NF and NF-immunoreactive products occurred in nerve fibers and increased numbers of fibrils were observed in endoneurial endothelial cells of the sural nerve. In addition, abnormal vimentin-immunoreactive deposition was seen in fibroblasts and capillaries of the skin. The present results suggest that high doses of n-hexane cause a diffuse IF disorder in a similar form as occurs in giant axonal neuropathy.

CONCLUSION

IF aggregation can occur in non-neuronal cells in humans, as has been previously proved in in vitro experiments. The presence of IF accumulations in Schwann cells, as seen in the ultrastructural examination, together with the electrophysiological findings showing an early decrease of sensory and motor nerve conduction velocities, suggests the existence of a primary myelinic disorder associated with axonal damage.

T235 variant of the angiotensinogen gene and blood pressure in the Chilean population

BACKGROUND

The angiotensinogen gene has recently been linked to essential hypertension. A variant within this gene, encoding threonine rather than methionine at amino acid position 235, was associated with essential hypertension. However, results of new studies have not confirmed this association, suggesting that ethnic differences may explain the different results.

OBJECTIVE

To evaluate whether the T235 variant is associated with a higher incidence of essential hypertension among Hispanics (a group that has scarcely been evaluated) and to determine whether T235 is associated with variations in the plasma renin activity or the serum aldosterone level.

PATIENTS AND METHOD

We studied 64 patients with essential hypertension and 62 normotensives, matched for age and sex. We obtained samples for determinations of plasma renin activity, serum aldosterone level and genome DNA from all subjects. The genomic DNA was amplified using the polymerase chain reaction technique and digested by the restriction enzyme streptococcus faecalis (Sfa NI) which cuts M235 only, not T235.

RESULTS

The patients with essential hypertension had a higher prevalence of the risk variant T235 (alleles 77/128 = 60.2%) than did the normotensive controls (alleles 65/124 = 52.4%), but the difference was not statistically significant (chi2=1.53, P=0.22). The plasma renin activity levels in hypertensives were not statistically different for homozygous T235, heterozygous and homozygous M235 (1.0 +/- 0.96, 2.0 +/- 2.25 and 1.55 +/- 1.49 ng/ml per h, respectively, P=0.5 1). However, when we considered those hypertensives with low plasma renin activity levels (< 1 ng/ml per h), we found a high prevalence (72.7%) of subjects homozygous for the T235 variant. We found no association between the T235 variant and the serum aldosterone levels in hypertensive and normotensive subjects.

CONCLUSIONS

We demonstrated that there is a high prevalence of T235 variant in our Hispanic population. The slight difference between prevalences of T235 variant among hypertensive and normotensive subjects that we found was not statistically significant and did not permit us to establish an association between T235 variant and essential hypertension. We believe that only studying a larger cohort of subjects could show whether there is a quantitative effect of the T allele on plasma renin activity levels.

[Electrophysiological study of 921 cases of carpal tunnel syndrome: its application for prognosis and treatment]

A neurophysiological study of 921 hands with clinical manifestations of carpal tunnel syndrome (CTS), 88 of normal individuals and 588 of patients with disorders not related with median neuropathy was carried out to establish the diagnostic sensibility 130 non-operated on patients with slight CTS were controlled one year later. The same was achieved with 105 surgically treated patients in order to establish the electrophysiological changes related to therapeutic methods. Antidromic sensory conduction and segmentary motor conduction of the median nerve were studied along with the difference between median and ulnar sensory latencies. Only 84 of the 921 hands (5.2%) showed normal electrophysiological findings and 469 (50.9%) minimal changes. 343 hands (37.2%) showed signs suggestive of axonal degeneration in sensory fibers and 147 (16%) in motor ones. Of the 130 slight CTS not surgically treated, clinical manifestations persisted for one year in 118, 17 of which have normal electrophysiological parameters. Twenty six (20%) of these 130 hands got worse. Of the 105 CTS surgically treated hands, 58 continued with symptoms one year later in spite of the electrophysiological improvement in 88.6% of them. Among 588 patients hands without CTS symptoms, only 0.8% had electrophysiological signs suggesting CTS. A high yield of the electrophysiological diagnosis of the CTS is shown. Symptoms frequently persist in patients without definite nerve compression.

[Measurement of low levels of plasma renin activity. A methodological improvement]

BACKGROUND

The present method to measure plasma renin activity is cumbersome and imprecise, factors that limit its clinical application.

AIM

To assess the importance of blood sampling conditions and the usefulness of increasing incubation time to measure plasma renin activity at low levels.

PATIENTS AND METHODS

Twenty hypertensive patients, 14 female, aged 14 to 76 years old, were studied. Two blood samples were obtained after a 10 min rest in the sitting position and after a 30 min rest in supine position. One blood sample of each condition was sent to the laboratory at room temperature and the other sample was sent refrigerated. Angiotensin I concentration was determined after 3 h of enzymatic incubation at 37 degrees C and, in subjects with an activity of less than 1 ng/ml/h, after 18 h of incubation.

RESULTS

No significant differences in plasma renin activity were observed between the samples obtained with different rest times or different transportation methods. In people with low plasma renin activity, the 18 h enzymatic incubation reduced the lower detection from 0.3 to 0.014 ng/ml/h and the coefficient of variation from 14.4 to 3.2%.

CONCLUSIONS

A simplified blood sampling method does not change plasma renin activity values, and the longer enzymatic incubation in people with low plasma renin activity improves both the sensitivity and accuracy of the determination.

[Hypertension treatable with glucocorticoids: report of a case]

Lately, a series of hypertensive syndromes of unknown etiology that respond to new forms of therapy, have been described. One of these is glucocorticoid remediable hypertension, that evolves with suppressed plasma renin activity and normal or high serum aldosterone levels, that lead to an aldosterone/plasma renin activity ratio over 30. We report a 45 years old woman with a severe hypertension, despite the use of antihypertensive medications. She had a plasma renin activity of less than 0.3 ng/ml/h, normal serum aldosterone levels (10 ng/ml) and thus a high aldosterone/plasma renin activity ratio. She had normal serum potassium and sodium levels. Due to the bad results of conventional antihypertensive medications, a treatment with dexamethasone was started, that normalized blood pressure and allowed to discontinue other antihypertensive medications. This type of hypertension must be sought since non conventional treatments could be used for refractory hypertensive syndromes.

Apoptosis is not the mechanism of cell death of muscle fibers in human muscular dystrophies and inflammatory myopathies

Muscle biopsies from patients affected by muscular dystrophies and polymyositis were processed with the method of in situ labeling of nuclear DNA fragmentation in order to assess whether apoptosis occurs in these diseases. Apoptotic nuclei were seen in the mononuclear cell infiltrates in inflammatory myopathies but not in dying muscle fibers, thus confirming the general opinion that death of muscle fibers in human diseases is not produced by a mechanism of apoptosis.

Post-irradiation neuromyotonia in bilateral facial and trigeminal nerve distribution

We describe a patient with episodic involuntary contraction in the lower facial and masseter muscles, in whom we recorded neuromyotonic discharges. The neuromyotonia was a delayed effect of radiation therapy and responded to carbamazepine therapy.

Genetic variation in P450c11AS in Chilean patients with low renin hypertension

Low renin hypertension (LRH), which accounts for 10-20% of patients with idiopathic "essential" hypertension, bears hormonal similarities to mineralocorticoid-induced hypertension, but elevated mineralocorticoid concentrations have not been found. Some patients with LRH have normal, rather than suppressed, plasma aldosterone concentrations, so that the ratio of aldosterone concentration to PRA (Aldo/PRA) is high, suggesting inappropriately increased aldosterone biosynthesis. We characterized the CYP11B2 gene that encodes the aldosterone synthase, P450c11AS, in hypertensive and control populations in a single clinic in Santiago, Chile. We directly sequenced the entire CYP11B2 gene in 12 patients with LRH, 2 high renin hypertensive controls, and 2 normotensive controls. All sequences were identical, except that 8 of 24 LRH alleles encoded arginine rather than lysine at position 173. The Arg173 and Lys173 variants were expressed in transfected MA-10 cells, and their ability to convert deoxycorticosterone to aldosterone was measured; the apparent Michaelis constant (Km) for Lys173 was 2.73 mumol/L; the Km for Arg173 was 2.53 mumol/L. The apparent maximal velocity (Vmax) for Lys173 was 6.5 x 10(-3) micrograms/mL.24 h; the Vmax for Arg173 was 7.8 x 10(-3) micrograms/mL.24 h. The first order rate constant, Vmax/Km was 2.38 for Lys173 and 3.08 for Arg173. As these values were not significantly different, we sought to determine whether Arg173 is a polymorphism linked to LRH. We examined position 173 in 52 unselected patients with idiopathic hypertension and 55 normotensive controls by PCR amplification of CYP11B2 exons 3-5 followed by digestion with Bsu361, which digests the Arg173 sequence, but not the Lys173 sequence. More of the hypertensive alleles (39 of 104, 37.5%) than normotensive alleles (25 of 110, 22.5%) carried Arg173 (chi 2 = 5.57; P < 0.02). Most of the Arg173 alleles (31 of 72, 43.1%) were from hypertensive patients with Aldo/PRA below 30, whereas only 5 of 24 (20.8%) Arg173 alleles were found in patients with Aldo/PRA greater than 30 (chi 2 = 3.79; P = 0.05) Thus, the ARg173 variant of CYP11B2 may be linked to LRH in Chilean patients.

Axon reflexes or ephaptic responses simulating blink reflex R1 after XII-VII nerve anastomosis

It has been claimed that functional recovery of the blink reflex occurs after hypoglossal-facial nerve anastomosis. This has been explained through central nervous system plasticity and reorganization of neuronal connections. In 5 patients with reinnervated facial muscles after hypoglossal-facial nerve anastomosis we observed "R1-like" responses that fulfilled criteria for facial nerve axon reflexes or ephapses. First, displacement of the stimulating electrode from the supraorbital to zygomatic area shortened the latency of the evoked response. Second, these responses were stable (jitter mean consecutive difference < 25 microsec) and they had complex potential shapes unmodified by high-frequency stimulation. Finally, collision techniques demonstrated antidromic conduction of impulses in the facial nerve from supraorbital to zygomatic points. Therefore, these "R1-like" responses are not the early component of a functionally recovered blink reflex but motor axon reflexes or ephaptic responses similar to the short latency responses observed following facial nerve regeneration or from sutured nerves in human forearms.