Expert consensus statement on acute hepatic porphyria in Belgium.

Acute hepatic porphyrias (AHP) are a group of four different rare to ultra-rare, severely debilitating, and sometimes fatal diseases that significantly impact patients' lives: 5-aminolevulinic acid (ALA) dehydratase deficiency porphyria (ADP), acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), and variegate porphyria (VP). Based on literature estimates, a conservative estimate of the number of AHP patients in Belgium requiring treatment, defined as patients experiencing recurrent attacks and/or chronic debilitating symptoms, is likely limited to 11-34 patients. These patients face a considerable unmet need, as there is currently no pharmaceutical treatment available that effectively prevents attacks and has an impact on other chronic symptoms of the disease.A panel consisting of the two European Porphyria Network1 (EPNet) centers in Belgium (Center for inborn errors of metabolism of UZ Leuven and the 'Centre Belge des Porphyries' of Erasme Hospital and LHUB-ULB) participated in an advisory board on 24 January 2020. Representatives of the sponsoring pharmaceutical company, Alnylam Pharmaceuticals, organized and attended the meeting. The objective of the meeting was to obtain expert input on the state-of-the-art clinical practice of AHP in Belgium. Following this meeting, this expert consensus statement was drafted, in collaboration with and coordinated by the EPNet centers in Belgium. This statement provides an overview of the state-of-the art in AHP, by means of a concise overview of AHP pathophysiology, clinical manifestations, and burden of disease, (Belgian) epidemiology, treatments, and proposed organization of care.

Molecular analysis of 19 Spanish patients with mixed porphyrias.

Porphyrias are rare diseases caused by alterations in the heme biosynthetic pathway. Depending on the afected enzyme, porphyrin precursors or porphyrins are overproduced, causing acute neurovisceral attacks or dermal photosensitivity, respectively. Hereditary Coproporphyria (HCP) and Variegate Porphyria (VP) are mixed porphyrias since they can present acute and/or cutaneous symptoms. These diseases are caused by a deficiency of coproporphyrinogen oxidase (CPOX) in HCP, and protoporphyrinogen oxidase (PPOX) in VP. Herein, we studied nineteen unrelated Spanish patients with mixed porphyrias. The diagnosis of either, HCP or VP was made on the basis of clinical symptoms, biochemical findings and the identification of the mutation responsible in the CPOX or PPOX genes. Two patients presented both acute and cutaneous symptoms. In most patients, the biochemical data allowed the diagnosis. Among eleven patients with HCP, ten CPOX mutations were identified, including six novel ones: two frameshift (c.32delG and c.1102delC), two nonsense (p.Cys239Ter and p.Tyr365Ter), one missense (p.Trp275Arg) and one amino acid deletion (p.Gly336del). Moreover, seven previously described PPOX mutations were identified in eight patients with VP. The impacts of CPOX mutations p.Trp275Arg and p.Gly336del, were evaluated using prediction softwares and their functional consequences were studied in a prokaryotic expression system. Both alterations were predicted as deleterious by in silico analysis. Aditionally, when these alleles were expressed in E. coli, only p.Trp275Arg retained some residual activity. These results emphasize the usefulness of integrated the biochemical tests and molecular studies in the diagnosis. Furthermore, they extend knowledge on the molecular heterogeneity of mixed porphyrias in Spain.

Long-Term Health Effects of PCBs and Related Compounds: A Comparative Analysis of Patients Suffering from Yusho and the General Population.

Yusho, which refers to a mass poisoning caused by the ingestion of rice bran oil contaminated with polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans, was first reported in October 1968 in Japan. Yusho patients suffer from various symptoms; however, after 40 years, some emerging symptoms have been attributed to aging. The prevalence of symptoms and diseases among Yusho patients and the general population was compared in this study. The data obtained from the survey among Yusho patients (1131 patients) by the Ministry of Health, Labour, and Welfare of Japan in 2008 were compared with the data from a survey conducted among the general population. When selecting the comparison group, the age and residential area (prefecture) were taken into account to match the baseline characteristics of Yusho patients. A logistic regression analysis was performed to identify the association between Yusho and the prevalence of symptoms and was adjusted for various potential confounding factors (age, sex, body mass index, cigarette smoking, frequency of drinking, and walking time). Skin pigmentation and acneiform eruption were found to be characteristic symptoms of Yusho and were more prevalent in these patients. Other symptoms and diseases associated with Yusho included orthostatic hypotension, hypohidrosis, dysgeusia, Basedow's disease, hoarseness, cardiac insufficiency, tachycardia, eczema, and hair loss. Symptoms related to aging, such as general fatigue, arthralgia, and numbness in the extremities, were significantly higher in Yusho patients after adjusting for age and lifestyle. This study demonstrated that, 40 years after the outbreak of Yusho, the prevalence of various symptoms and diseases in Yusho patients, including age-related diseases, was higher than that in the general population.

Clinical, Biochemical and Molecular Characteristics of the Main Types of Porphyria.

Porphyrias are diverse disorders that arise from various inherited enzyme defects in the heme biosynthesis pathway, except for porphyria cutanea tarda (PCT), in which the enzyme deficiency in most cases is acquired. The biosynthetic blocks resulting from the defective enzymes are largely expressed either in the liver or bone marrow, the sites where the majority of heme is produced. Although the pathophysiologic mechanisms of the clinical manifestations of the porphyrias are not fully understood, two cardinal features prevail: skin photosensitivity and neurologic symptoms of intermittent autonomic neuropathy, acute neurovisceral attacks, and disorders of the nervous system. The primary diagnosis of the proband is based on biochemical testing, which is not always able to identify acute porphyrias, especially in asymptomatic family carriers when heme precursors and porphyrins excretion is normal, low-normal and high-reduced values of enzyme activity overlap, and hematological diseases responsible for abnormal blood cells distribution coexist. Molecular analysis of gene mutations responsible for each type of porphyria is the best diagnostic approach for symptomatic as well as presymptomatic gene carriers.

Cutaneous Porphyrias: Causes, Symptoms, Treatments and the Danish Incidence 1989-2013.

Porphyrias are rare diseases caused by altered haem synthesis leading to the accumulation of different haem intermediates. Neurovisceral attacks may occur in acute porphyrias, while photosensitivity is the presenting symptom in cutaneous porphyrias. We present here an overview of symptoms and a flowchart for the diagnosis of cutaneous porphyrias, with recommendations for monitoring and an update of treatment options. From the Danish Porphyria Register, we present the incidences and approximate prevalences of cutaneous porphyrias within the last 25 years. A total of 650 patients with porphyria cutanea tarda were identified, 73 with erythropoietic protoporphyria, 9 with variegate porphyria, 4 with hereditary coproporphyria and one with congenital erythropoietic porphyria. The total incidence of all porphyrias was ~0.52/100,000 per year.

[Porphyrias and haem related disorders]. / Les porphyries héréditaires: anomalies du métabolisme de l'hème.

The hereditary porphyrias comprise a group of eight metabolic disorders of the haem biosynthesis pathway characterised by acute neurovisceral symptoms, skin lesions or both. Each porphyria is caused by abnormal function of a separate enzymatic step resulting in a specific accumulation of haem precursors. Seven porphyrias are the consequence of a partial enzyme deficiency while a gain of function mechanism has been recently characterised in a novel porphyria. Acute porphyrias present with severe abdominal pain, nausea, constipation, confusion and seizure, which may be life threatening. Cutaneous porphyrias can be present with either acute painful photosensitivity or skin fragility and blisters. Rare recessive porphyrias usually manifest in early childhood with either severe chronic neurological symptoms or chronic haemolysis and severe cutaneous photosensitivity. Porphyrias are still underdiagnosed, but once they are suspected, and depending on the clinical presentation, a specific and simple front line test allows the diagnosis in all symptomatic patients. Diagnosis is essential to institute as soon as possible a specific treatment. Screening families to identify presymptomatic carriers is crucial to prevent chronic complications and overt disease by counselling on avoiding potential precipitants.

Effects of dioxin-related compounds on bone mineral density in patients affected by the Yusho incident.

Exposure to dioxin-related compounds results in many adverse health effects. Several studies have examined the effects of dioxin-related compounds on human bone metabolism with inconsistent results. In Japan in 1968, accidental human exposure to rice oil contaminated with dioxin-related compounds led to the development of Yusho oil disease. The aim of this study was to determine whether exposure to dioxin-related compounds was associated with bone mineral density in Yusho patients. In 2010, 262 women and 227 men underwent dual-energy X-ray absorptiometry bone scans as part of the nationwide Yusho health examination. Serum levels of polychlorinated dibenzo-p-dioxin, polychlorinated dibenzofurans, and non-ortho polychlorinated biphenyls were measured using high-resolution gas chromatography and high-resolution mass spectrometry. When adjusted for prefecture, 1,2,3,4,7,8-HxCDD and 2,3,7,8-TCDF were significantly positively associated with Z-scores in men. No congeners were positively associated with Z-scores in women. After adjustment for prefecture and body mass index, one congener, 1,2,3,4,6,7,8-HpCDD, was negatively associated with Z-scores in women. In contrast, no congeners remained significant in men after adjusting for body mass index. This may suggest that 1,2,3,4,6,7,8-HpCDD has a negative effect on bone mineral density in women; however, the findings should be interpreted carefully, because no increase in the serum level of this congener was observed in patients with Yusho disease.

[Lessons from Field Studies].

During my academic career for more than 40 years, I was involved in 18 epidemiological field studies, partially or fully. Among these field studies, four (1. Medical services in remote rural areas in Okinawa, 2. Yusho episode, 3. JICA Onchocerciasis Control Project in Guatemala, and 4. Miyako cohort study in Fukuoka) are introduced in this paper, including the latest situation after the presentation. Through these field works experienced by the author, the following lessons were gained. 1. Strong human reliance between researchers and the targeted population is essential in carrying out epidemiological surveys successfully in the field. 2. Data obtained from the survey should be carefully examined and analyzed so that those data may reflect the real situation.

[Comparison of the prevalence of symptoms and medical histories between Yusho patients and healthy controls].

Yusho disease was first reported in October 1968 in western Japan. Although a previous survey revealed that Yusho patients have suffered from various symptoms for 40 years after the outbreak of Yusho, some symptoms could be caused by aging. Therefore, we compared the prevalence of symptoms and medical histories (symptoms or patient-reported diseases) between Yusho patients and healthy controls to demonstrate the effects of Yusho on health conditions. We conducted a survey of healthy controls who had already registered to a survey company and created a dataset of symptoms and medical histories. We then merged the healthy control data with the Yusho survey data obtained from The Ministry of Health, Labour, and Welfare of Japan. Statistical analyses were performed using a chi-square analysis for the incidence of symptoms. Symptoms included in the major diagnostic criteria for Yusho, such as pigmentation and acneform eruption, were expectedly higher in the Yusho patients than in the healthy individuals. Symptoms that could be caused by aging, such as general fatigue, arthralgia, and numbness in the extremities, were also significantly higher in the Yusho patients after adjustment for age, indicating the possibility that Yusho may cause various systemic symptoms and diseases.

Acute Porphyrias.

BACKGROUND: Porphyrias are a group of eight metabolic disorders characterized by defects in heme biosynthesis. Porphyrias are classified into two major categories: 1) the acute or inducible porphyrias and 2) the chronic cutaneous porphyrias. The acute hepatic porphyrias are further classified into acute intermittent porphyria (AIP), hereditary coproporphyria, variegate porphyria, and porphyria due to severe deficiency of delta-aminolevulinic acid (ALA) dehydratase (ALADP). DISCUSSION: AIP is the most common, and ALADP is the least common acute porphyria. The clinical presentations of acute porphyrias are nonspecific. There are no pathognomonic signs or symptoms. The most frequent presenting symptom is abdominal pain, but pain in the chest, back, or lower extremities may also occur. Hyponatremia is the most common electrolyte abnormality during acute attacks, and hypomagnesemia is also common. Both are risk factors for development of seizures, which occur in ∼ 20-30% of acute attacks. CONCLUSION: Once suspected, the diagnosis of porphyria can be rapidly established by checking random urinary porphobilinogen. Initial management of acute porphyria includes discontinuation of all potentially harmful drugs and management of symptoms. Acute attacks should be treated emergently with intravenous heme and glucose to avoid considerable morbidity and mortality. Acute attacks last a few days, and the majority of patients are asymptomatic between attacks. Prognosis is good if the condition is recognized early and treated aggressively.

Porphyria Diagnostics-Part 1: A Brief Overview of the Porphyrias.

Porphyria diseases are a group of metabolic disorders caused by abnormal functioning of heme biosynthesis enzymes and characterized by excessive accumulation and excretion of porphyrins and their precursors. Precisely which of these chemicals builds up depends on the type of porphyria. Porphyria is not a single disease but a group of nine disorders: acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), variegate porphyria (VP), δ-aminolevulinic acid dehydratase deficiency porphyria (ADP), porphyria cutanea tarda (PCT), hepatoerythropoietic porphyria (HEP), congenital erythropoietic porphyria (CEP), erythropoietic protoporphyria (EPP), and X-linked protoporphyria (XLP). Each porphyria results from overproduction of heme precursors secondary to partial deficiency or, in XLP, increased activity of one of the enzymes of heme biosynthesis. Taken together, all forms of porphyria afflict fewer than 200,000 people in the United States. Based on European studies, the most common porphyria, PCT, has a prevalence of 1 in 10,000, the most common acute porphyria, AlP, has a prevalence of ∼1 in 20,000, and the most common erythropoietic porphyria, EPP, is estimated at 1 in 50,000 to 75,000. CEP is extremely rare, with prevalence estimates of 1 in 1,000,000 or less. Only six cases of ADP are documented. The current porphyria literature is very exhaustive and a brief overview of porphyria diseases is essential in order for the reader to better appreciate the relevance of this area of research prior to undertaking biochemical diagnostics procedures. This unit summarizes the current knowledge on the classification, clinical features, etiology, pathogenesis, and genetics of porphyria diseases.

Porphyrias in Norway.

BACKGROUND: Porphyria is an umbrella term for a group of largely hereditary diseases that are due to defective haem synthesis. The diseases have a varied and partly overlapping range of symptoms and presentations. The commonest forms of porphyria are porphyria cutanea tarda, acute intermittent porphyria and erythropoietic protoporphyria. The purpose of this study is to provide an overview of the prevalence and pathological manifestations of porphyrias in Norway. MATERIAL AND METHOD: Information on all patients registered with the Norwegian Porphyria Centre (NAPOS) up to 2012 was used to estimate the prevalence and incidence of porphyrias in Norway. Figures on symptoms, precipitating factors and follow-up routines were obtained from the Norwegian Porphyria Registry, which includes 70% of Norwegians registered with NAPOS as having porphyria. RESULTS: The prevalence of porphyria cutanea tarda was approximately 10 : 100,000 and that of acute intermittent porphyria approximately 4 : 100,000. The total incidence of all porphyrias was approximately 0.5-1 : 100,000 per year. Diagnostic delay, i.e. the time passing between the onset of symptoms and diagnosis, varied from 1-17 years depending on the type of porphyria. There was wide variation in the frequency with which patients with the various types of porphyria went for medical check-ups. INTERPRETATION: The prevalence of acute intermittent porphyria and porphyria cutanea tarda appears to be higher in Norway than in most other countries. Data from the Norwegian Porphyria Registry makes it possible to demonstrate differences in treatment and follow-up of porphyria patients and may be used to initiate necessary measures.

[Porphyrin metabolism in women with metabolic syndrome].

A total of 47 women with metabolic syndrome (MS) were examined with the fractional determination of porphyrins in urine (uroporphyrin and coproporphyrin) and feces (coproporphyrin and protoporphyrin) as well as their precursors (5-aminolevulinic acid and porphobilinogen). Disorders of porphyrin metabolism were documented in 29 (61.7%) women All patients had elevated levels of porphyrin precursors. Five women exhibited qualitative changes in the form of abnormal ratios of different porphyrin fractions(coproporphyrin/uroporphyrin < 1--0.8 ± 0.1 vs normal ratio 3.6 ± 0.4). 21 patients suffered quantitative changes in porphyrin metabolism in the form of manifold increase of porphyrin levels in urine and/or feces and formation of biochemical syndromes of secondary coproporphyrinuiria, symptomatic rise in porphyrin content in feces, and chronic latent hepatic porfiria. Disorders of porphyrin metabolism were associated with insulin resistance. Changes of porphyrin metabolism in MS extend the spectrum of concomitant disturbances and can be regarded as an additional criterion.

Regional impact of exposure to a polychlorinated biphenyl and polychlorinated dibenzofuran mixture from contaminated rice oil on stillbirth rate and secondary sex ratio.

Yusho disease, a polychlorinated biphenyl (PCB) and polychlorinated dibenzofuran (PCDF) mixed poisoning caused by contaminated rice oil, occurred in Japan in 1968. The evidence on reproductive outcome is limited. We therefore evaluated the regional impact of the exposure to the PCB and PCDF mixture on stillbirth rate and secondary sex ratio among the residents in two severely affected areas. We selected the regionally-affected towns of Tamanoura (n=4390 in 1970) and Naru (n=6569) in Nagasaki Prefecture, Japan, for study. We obtained data on stillbirths (spontaneous/artificial) and live-born births (total/male/female) from 1958 to 1994. For a decade and a half after the exposure, an increase in the rate of spontaneous stillbirths coincided with a decrease in the male sex ratio. Compared with the years 1958-1967, the ratios for spontaneous stillbirth rates were 2.16 (95% confidence interval: 1.58 to 2.97) for 1968-1977 and 1.80 (95% confidence interval: 1.25 to 2.60) for 1978-1987. The sex ratio (male proportion) was 0.483 (95% confidence interval: 0.457 to 0.508) in the first 10years after exposure. Exposure to a mixture of PCBs and PCDFs affected stillbirth and sex ratio for a decade and a half after the exposure.

Novedades en las porfirias eritropoyéticas / New Developments in Erythropoietic Porphyrias

En los últimos años se han producido importantes avances en la genética de las porfirias y, concretamente, en las porfirias eritropoyéticas -protoporfiria eritropoyética (PPE) y porfiria eritropoyética congénita (PEC)-, que han dado lugar a una nueva concepción de las mismas como enfermedades no monogénicas. Se han identificado mutaciones en nuevos genes como responsables o modificadores de la gravedad de la porfiria, permitiendo esclarecer las discrepancias geno-fenotípicas observadas entre pacientes portadores de las mismas mutaciones, así como identificar el defecto genético responsable de algunos casos de porfiria en los que los estudios moleculares del gen uroporfirinógeno sintetasa (UROS) en la PEC o del gen ferroquelatasa (FECH) en la PPE no identificaban ninguna mutación. La mejor caracterización y conocimiento de la genética de estas enfermedades permitirá establecer cuadros geno-fenotípicos concretos y realizar una clasificación molecular con implicaciones prácticas y pronósticas (AU)

In recent years, important advances have been made in our understanding of the genetics of porphyrias, particularly with respect to erythropoietic protoporphyria (EPP) and congenital erythropoietic porphyria (CEP), 2 forms of erythropoietic porphyria no longer considered to be monogenic. The identification of mutations in genes not previously associated with these disorders as causative factors or modulators of severity has helped to explain the presence of genotypic and phenotypic differences between patients carrying the same mutations. These advances have also led to the identification of causative genetic defects in patients who, based on molecular studies, had no mutations in the uroporphyrinogen III synthase gene UROS (in CEP) or in the ferrochelatase gene FECH (in EPP). Better understanding and characterization of the genetics of porphyrias will allow us to determine genotypic and phenotypic correlations and improve the molecular classification of these diseases, which will have both practical and prognostic implications (AU)

Blood levels of PCDDs, PCDFs, and coplanar PCBs in Yusho mothers and their descendants: association with fetal Yusho disease.

Maternal exposure to polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) may result in adverse health effects in their children. In Japan in 1968, an accidental human exposure to rice oil contaminated with PCDDs, PCDFs, and PCBs, led to the development of Yusho disease. Yusho mothers delivered descendants with low birth weights and hyperpigmented skin and mucosa, which are characteristic of fetal Yusho disease (FYD). The Yusho cohort was used to evaluate the effect of maternal exposure to PCDDs, PCDFs, and PCBs on the development of FYD. Blood samples, obtained from 64 Yusho mothers (117 descendants: 10 with FYD and 107 without FYD), were analyzed for congeners of seven PCDDs, 10 PCDFs, and four coplanar PCBs. We investigated the association between the maternal estimated blood levels of dioxins at delivery and the risk of fetal Yusho disease. We also studied the differences in dioxin blood levels in 24 mother-descendant pairs (5 with FYD and 19 without FYD). The estimated levels of total PCDD TEQ, total PCDF TEQ, total coplanar PCB TEQ, and total TEQ in the maternal blood at delivery were associated with significantly increased risk of FYD. The odds ratios, which present the risk of FYD for a 10-fold increase in blood dioxin, were largest for 1,2,3,6,7,8-HexaCDD (odds ratio=28.6, 95% confidence interval=1.67-489.9, p=0.02). The levels of 1,2,3,6,7,8-HexaCDD in both the Yusho mothers and their descendants with FYD were higher than the levels in those without FYD. These findings suggest that 1,2,3,6,7,8-HexaCDD is the most important causative congener for the development of FYD.

The incidence of inherited porphyrias in Europe.

Retrospective estimates of the prevalence of porphyrias have been reported but there has been no large scale prospective study of their incidence. The European Porphyria Network collected information prospectively over a 3 year period about the number of newly diagnosed symptomatic patients with an inherited porphyria (335 patients from 11 countries). Prevalence was calculated from the incidence and mean disease duration. The incidence of hepato-cellular carcinoma (HCC) in acute hepatic porphyria and the prevalence of patients with recurrent acute attacks of porphyria were also investigated. The incidence of symptomatic acute intermittent porphyria (AIP) was similar in all countries (0.13 per million per year; 95 % CI: 0.10 - 0.14) except Sweden (0.51; 95 % CI: 0.28-0.86). The incidence ratio for symptomatic AIP: variegate porphyria: hereditary coproporphyria was 1.00:0.62: 0.15. The prevalence of AIP (5.4 per million; 95 % CI: 4.5-6.3) was about half that previously reported. The prevalence of erythropoietic protoporphyria (EPP) was less uniform between countries and, in some countries, exceeded previous estimates. Fourteen new cases of HCC (11 from Sweden) were reported in patients with acute porphyria. Sixty seven patients (3 VP; 64 AIP: 53 females, 11 males) with recurrent attacks of acute porphyria were identified. The estimated percentage of patients with AIP that will develop recurrent acute attacks was 3-5 %. In conclusion, the prevalence of symptomatic acute porphyria may be decreasing, possibly due to improved management, whereas the prevalence of EPP may be increasing due to improved diagnosis and its greater recognition as a cause of photosensitivity.

Maternal exposure to high levels of dioxins in relation to birth weight in women affected by Yusho disease.

BACKGROUND: Studies on the association of maternal exposure to polychlorinated dibenzo-p-dioxin (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) with decreased birth weight in humans have produced conflicting results. In Japan in 1968, an accidental human exposure to rice oil contaminated with PCDDs, PCDFs, and PCBs, led to the development of Yusho disease. OBJECTIVE: The Yusho cohort was used to evaluate the effect of maternal exposure to PCDDs, PCDFs, and PCBs on birth weight. METHODS: Blood samples, obtained from 101 Yusho women (190 births) who gave birth after exposure, were analyzed for congeners of seven PCDDs, ten PCDFs, and four non-ortho PCBs. RESULTS: Total PCDD TEQ (adjusted beta=-161.9g; 95% CI, -265.3 to -58.6), total PCDF TEQ (adjusted beta=-105.9g; 95% CI, -179.5 to -32.2), and total non-ortho PCBs (adjusted beta=-178.4g; 95% CI, -318.3 to -38.5) levels were inversely associated with birth weight. Significant inverse associations with birth weight were also found for total PCDD TEQ, total PCDF TEQ, and total non-ortho PCB TEQ levels among male, but not female, infants. Significant inverse associations with birth weight were also found for nine congeners among all infants; the adjusted beta coefficients were largest for 1,2,3,6,7,8-HxCDD and smallest for 2,3,4,7,8-PeCDF. CONCLUSION: In the setting of exposure to high levels of dioxins, maternal blood levels of PCDDs, PCDFs and PCBs are associated with lower birth weight in Yusho patients. The association exhibited gender-specific differences, as male infants are more susceptible than females to growth restriction induced by in utero dioxin exposures.