Fatal methanol poisoning

Introduction

Methanol poisoning is a worldwide problem and can cause morbidity and mortality in developing countries. Methanol or wood alcohol is a clear, colorless and volatile liquid. It is a component of many industrial products like paints, solvents, cleansers perfumes, antifreeze, many other commercially available solvents and illegal alcohols (Andersen et al., 2008; Karayel et al., 2010; Liu et al., 1999; Yayci et al., 2003).

Methanol poisoning may occur accidentally or intentionally (suicide, abuse or misuse) (Azmak, 2006; Karayel et al., 2010). In Iran, methanol is widely used in many industries and is cheap and easy to obtain. Consumption of alcoholic beverages is prohibited due to law and religious reasons in Iran. Because of these limitations, production of illicit alcoholic beverages in clandestine laboratories has become common in some parts of Iran. Production of alcoholic beverages is accompanied with adulteration of products with a highly toxic alcohol like methanol. Drinking of this adulterated beverage instead of pure ethanol leads to methanol poisoning and if not diagnosed and treated results in high mortality rate. There is evidence that methanol poisoning is due to its conversion to highly toxic metabolites, formaldehyde and formic acid (Kinoshita et al., 1998; Skrzydlewska, 2003). Severe metabolic acidosis induced by formic acid leads to death (Azmak, 2006; Kinoshita et al., 1998). Methanol and ethanol metabolisms show similarities. In the metabolism of both alcohols, oxygen free radicals are generated and can induce liver injury (Chrostek et al., 2001; Skrzydlewska et al., 2000; Skrzydlewska and Fabriszewski, 1998). Histopathologic examination of liver tissue in human and animal models intoxicated with methanol revealed cell injury that mainly involved inner and outer cell membranes (Datta and Namasivayam 2003; Poon et al., 1994, 1995).

There are some reports concerning methanol poisoning and its toxic consequences (Moghadami, et al., 2008; Taheri et al., 2010), but there are not many studies on the pathologic findings of methanol intoxication on liver tissue in Iran. Systematic standard histological examination of main organs should be used in routine forensic autopsies (de la Grandmaison et al., 2010). As a result, a descriptive study was designed to evaluate 44 deaths due to methanol poisoning. Liver histopathology and toxicology investigations were represented from medicolegal point of view.

Materials and methods

A cross-sectional study was conducted on fatal methanol poisoning cases that were referred to Legal Medicine Organization (LMO) of Iran, Tehran, for one year starting in March 2008. Inclusion criteria were history of methanol poisoning. Methanol poisoning was confirmed by quantitative methanol detection in blood and vitreous humor of all cases. Among 52 cases, only 44 cases were investigated from pathologic point of view due to liver tissue autolysis, presence of evidence that the case had the history of drug use or substance abuse or coexistent disease in the remaining 8 cases. Femoral blood, vitreous humor, liver and other biological samples (urine, bile and stomach content) were collected at autopsy and examined in forensic toxicology and pathology departments of LMO, Tehran, Iran.

Results

Histological changes of liver obtained from 44 cases of methanol poisoning were evaluated in a year. Light microscope examination of the 44 liver tissue sections, stained with hematoxylin–eosin (H&E), indicated that the two main morphologic changes of nonlethal cell injury were fatty change (steatosis) and cellular swelling (hydropic change and feathery degeneration) solely or in combination with other injuries. Micro-vesicular steatosis was much more pronounced than macro-vesicular steatosis; however, coexistence of two or three morphologic features in a single case is more common (Figure 1). It should be noted that in 18 (40.9%) cases only one histopathology change was seen and more than one morphologic features were found in 26 (59.1%) of our study cases.

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Figure 1.

Micro-and macro-vesicular steatosis (hematoxylin and eosin).

Hepatocyte degeneration (cellular swelling) was divided into two main features; hydropic degeneration (ballooning) and feathery (vacuolar) degeneration. Cell enlargement (swelling) along with irregularly clumped cytoplasm and uneven clear cytoplasmic spaces with or without intracellular bile retention were considered as feathery or hydropic degeneration, respectively. Nevertheless, hepatocyte bile stasis was also recorded in some cases in the absence of the degenerative changes.

The presence of focal hepatocyte destruction in the form of coagulative and dropout necrosis around the central vein in hepatic lobules (centrilobular) with or without inflammatory infiltrates was also notable. We could also find a scant amount of eosinophilic cytoplasmic inclusion (Mallory body), sinusoidal, perivenular and/or periportal fibrosis; nonetheless, the amount of changes were not so significant to be considered in the results. A summary of the main patterns of morphologic liver injury and the prevalence of findings in 44 cases of methanol intoxication are provided in Table 1. A univariate analysis of variance (controlled for sex and age variables as covariate) was done on data obtained from this study to estimate the association between methanol concentration and the type of histopathology changes in liver tissue. Results showed that there was no statistically significant difference between mean blood and vitreous humor methanol concentrations in six features of histopathology findings (p > 0.05). However, in cases with more than one pathologic features, the mean blood and vitreous humor methanol concentration was 127 ± 38.9 mg/dL, higher than the cases with one pathologic finding (p = 0.0021). Of the 44 cases included in this analysis, 38 (86.36%) were men and 6 (13.64%) were women (male-to-female ratio: 6.33). Mean age of the cases was 37.36 ± 14.95 (mean ± SD) years with a range between 10 and 66 years. Blood and vitreous humor methanol concentrations were 149.5 ± 143.38 mg/dL and 154.62 ± 144.33 mg/dL (mean ± SD), respectively. Accidental poisoning was the cause of death in 38 (86.36%) cases while the remaining 6 (13.64%) deaths were classified as suicidal.

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Table 1.

Summary of liver histopathology findings of fatal methanol poisoning cases, by light microscopy.

Histopathology finding	Number of cases (%)
Micro-vesicular steatosis	32 (72.7)
Macro-vesicular steatosis	15 (34.1)
Focal hepatocytes necrosis/drop out necrosis	6 (13.64)
Mild intrahepatocyte bile stasis	6 (13.64)
Feathery (vacuolar) degeneration	6 (13.64)
Hydropic changes	4 (9.1)

Discussion

This study was performed to evaluate methanol-induced liver injury in Iranian population. Methanol poisoning has been a big problem in some countries, and the morbidity and mortality rates of methanol poisoning are dependent on the accessibility to this solvent. Consumption of ethanol has been banned by sharia (God's law) and law in Iran, thus poisoning with methanol as a constituent of handmade ethanol and ingestion of pure methanol as a solvent is not rare.

In this study, we had 52 fatal methanol poisoning cases in one year that is about 7.4 times more than the one reported by Liu et al. (1999). Not surprisingly, in some countries methanol is sold only to laboratories or individuals with a specific license. Regarding these limitations, only 3 cases of fatal methanol poisoning were found during six years in Denmark (Kristensen and Hansen, 1994; Liu et al., 1999). Methanol is not readily available in the Netherlands and methanol intoxications are extremely rare in this country (Epker and Bakker, 2010). In our study, fatal methanol poisonings were 6.3 times higher among males than females and most of the victims were middle-aged. These findings are in accordance with other similar studies (Azmak 2006; Liu et al., 1999).

There are reports that methanol poisoning can cause tissue damage in some organs. According to the study of Taheri et al. (2010), putaminal hypodense lesions and putaminal hemorrhage were the most common manifestations of methanol poisoning in brain computerized tomography. Metabolism of methanol to formaldehyde and formate is accompanied by the formation of superoxide anion which can be involved in lipid peroxidation (Skrzydlewska and Fabriszewski, 1998). Other studies revealed that methanol metabolites can induce liver toxicity characterized by membrane damage (Chrostek et al., 2001). Ethanol-induced liver disease had been well documented in previous studies. Early steatosis, inflammation and necrosis were reported as features of liver damage in the study of Arteel. This study revealed that oxidative stress was involved in liver disease (Arteel, 2003; Castro et al., 2002). Considering the similarities between ethanol and methanol in the chemical structure and metabolism pathways, free radical production during methanol metabolism could be expected (Skrzydlewska et al., 2000).

As already mentioned, the liver, in common with other organs, is subject to injury from a large numbers of environmental chemicals and drugs. Methanol ingestion even in a small amount can be potentially lethal (Epker and Bakker, 2010). It should be noted that methanol itself is not very toxic, but its two metabolites, formaldehyde and formic acid, are extremely harmful. The clinical manifestations of acute methanol poisoning are not very specific and usually delayed for several hours, until the degradation metabolites are produced (Jones et al., 2007; Rubinstein et al., 1995; Schneck, 1989). Although hemodynamic disturbances can be safely and effectively controlled with current treatment, the mortality is still very high (Epker and Bekker, 2010). There are reports that methanol poisoning can cause tissue damage in some organs (Hanston, 2006; Parthasarathy et al., 2006). Methanol has already been recognized as a serious neurotoxin and the mortality of methanol poisoning is mainly connected with the devastating effects on the central nervous system (Karayel et al., 2010).

On the other hand, liver cells might be damaged by chemicals in three different ways: direct toxicity, production of toxic metabolites by liver cells, or activation of immune-mediated mechanisms (drug or chemical acting as a hapten). Obviously, direct toxicity and toxic metabolites are the main causes of methanol hepatotoxicity (Wight, 1994). The clinical manifestations and a battery of laboratory tests are generally used to diagnose chemical-induced hepatic injury; however, liver biopsy or necropsy specimens’ examinations are frequently preferred method to interpret the morphologic feature and the extent of injury (Kumar et al., 2007). Therefore, in order to be able to describe the hepatocyte responses at a more comprehensive level, we considered the reversible and irreversible cell changes as major morphological and functional responses of cells to injury. In our study cases, fatty change or steatosis (micro and macro-vesicular steatosis) in the hepatocytes was by far the most common histological findings. However, the existence of focal hepatocyte necrosis signifies that irreversible cell injury, to a lesser extent, should be expected in some cases. In other words, none of our cases had any evidence of zonal, sub-massive, or massive hepatic necrosis, and it is more likely that the liver changes begin to completely recover if the victims remain alive. It is certainly the case that the central nervous system shows the most serious and lethal damage in methanol intoxication, in spite of the fact that liver is the first organ exposed to methanol and its toxic metabolites. As we excluded any cases with known disease or history of drug use, it is possible to assume that these findings are related to methanol usage. Methanol level can be decreased in body fluids due to excretion, metabolism or treatment measures such as hemodialysis. According to the study of Jones et al. (2007), there is a relatively poor correlation between blood methanol concentration and toxicity or mortality; therefore, it was better to quantitate formate and formic acid levels in blood and vitreous humor. Unfortunately methods for detecting these compounds were not included in our routine laboratory methods. Different reactions of individuals to the same compound are a common phenomenon. There are some ideas about the effect of genetic background on the pharmacological processes of chemical compounds in the body. These interindividual variations can affect absorption, metabolism and elimination of substances (Johnson 2003). As a result, these can justify various histopathology liver changes in different methanol concentrations (Rubinstein et al., 1995).

We have to indicate that the results of our study must be interpreted in the context of several important limitations. Some vital clinical information about our study cases such as the survival time, serum level of liver enzymes, metabolism rate, blood level of formaldehyde, formic acid and methanol at admission time to hospital, clinical management (hemodialysis) before death and the quantity of the methyl alcohol intake were not actually included in our study owing to the inaccessibility of related hospital records. Pharmacogenetic analyses are not routinely used in forensic toxicology laboratories. The search for genetic polymorphism and interindividual variations can be the source of important information to clarify the cause of death which are difficult to diagnose with routine analytical methods. More importantly, our results would be more advantageous if we studied the liver and brain specimens of each case concurrently. Additional studies on cellular and molecular levels, quantitative analysis of formaldehyde and formic acid, indicators of oxidative stress, polymorphism in alcohol and aldehyde dehydrogenase and other ethnic factors in the Iranian population would be helpful; however, this will, of course, pave the way for the future studies.

In conclusion, ban on alcohol use in Iran provides ample breeding grounds for producing and selling a potentially lethal alcohol like methanol. As a result, accidental methanol poisoning has become a major issue in Iran and is also one of the notable problems forensic medicine has to face. Besides, there are not many clinical and pathologic studies on methanol intoxication in Iran.