Porphyria Hepatica

The acute oral and inhalation toxicity of hexachlorobenzene is low in test animals. Repeated ingestion of this compound may produce porphyria hepatica (increased formation and excretion of porphyrin) caused by disturbances in liver metabolism. The oral LD50 value in rabbits is 2600 mg/kg the inhalation LC50 value from a single exposure is 1800 mg/m (NIOSH 1986). The occupational health hazard from inhalation should be very low because of its very low vapor pressure (0.00001 torr). 

Clinical Pathology of Porphyria Porphyria Hepatica Acquired Porphyria... 

The two major types of porphyria, classified according to pathogenesis, are porphyria erythropoietica and porphyria hepatica. 

The most striking clinical symptom in patients with erythropoietic porphyria is photosensitivity, which the patient develops at an early age. Occasionally, photosensitivity exists at birth, but often it becomes apparent during the first years of life, in contrast to the photosensitivity of porphyria hepatica which develops later in life. 

Porphyria hepatica differs from erythropoietic porphyria in that the metabolic defect is found only in the hepatic cell, and therefore metabolites accumulate only in liver tissue. 

Porphyria hepatica can be subdivided into two extreme types acute intermittent porphyria characterized by the development of abdominal and nervous symptoms without photosensitivity and cutanea tarda characterized by photosensitivity without abdominal and nervous symptoms. Both diseases are hereditary and are probably transmitted by mendelian dominant genes (see Table 3-4). 

The patient with acute intermittent porphyria suffers a severe acute abdominal pain not definitely localized and without rigidity or tenderness of the abdominal wall. Moderate fever and leukocytosis develop. If the physician is not aware of the porphyria, he is likely to be confused and suspect appendicitis, renal or biliary colics, pancreatitis, perforated ulcer, acute bowel obstruction or another common cause of abdominal pain. The differential diagnosis of porphyria and bowel obstruction is further complicated because the attacks of porphyria hepatica are often associated with severe constipation. Abdominal X-rays of porphyric patients show colonic distension. The pathogenesis of the abdominal symptoms is not known. They could result either from a direct effect of porphobilinogen or porphyrin on the intestinal mucosa or be the consequence of an increased excitability of the autonomic system. 

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