Variegate porphyria (VP) is a serious autosomal dominant disorder of heme biosynthesis characterized by skin lesions that are identical to those of PCT (vesicles and bullae, skin fragility, milia and scarring of the dorsa of the hands and fingers), acute attacks of abdominal pain, neuropsychiatric manifestations, and increased excretion of porphyrins; especially characteristic are high levels of protoporphyrin in the feces.
Causes of Variegate Porphyria
The basic metabolic defect is accentuated by ingestion of certain drugs (sulfonamides, barbiturates, phenytoin, estrogens, alcohol, and others), with the resultant precipitation of acute attacks of abdominal pain and neuropsychiatric disorders (delirium, seizures, personality changes). There is an enzyme defect resulting in a reduction of protoporphyrin oxidase, with accumulation of protoporphyrinogen in the liver, which is excreted in the bile and is nonenzymatically converted to protoporphyrin; this accounts for the high fecal protoporphyrin.
Symptoms of Variegate Porphyria
The hepatic porphyrias primarily affect the nervous system, resulting in abdominal pain, vomiting, acute neuropathy, seizures, and mental disturbances, including hallucinations, depression, anxiety, and paranoia. Cardiac arrhythmias and tachycardia (fast heart rate) may develop as the autonomic nervous system is affected. Pain can be severe and can, in some cases, be both acute and chronic in nature. Constipation is frequently present, as the nervous system of the gut is affected, but diarrhea can also occur.
Diagnosis
Porphyria is diagnosed through spectroscopy and biochemical analysis of blood, urine, and stool.In general, urine estimation of porphobilinogen (PBG) is the first step if acute porphyria is suspected. As a result of feedback, the decreased production of heme leads to increased production of precursors, PBG being one of the first substances in the porphyrin synthesis pathway. In nearly all cases of acute porphyria syndromes, urinary PBG is markedly elevated except for the very rare ALA dehydratase deficiency or in patients with symptoms due to lead poisoning or hereditary tyrosinemia type I.
Repeat testing during an attack and subsequent attacks may be necessary in order to detect a porphyria, as levels may be normal or near-normal between attacks. The urine screening test has been known to fail in the initial stages of a severe life threatening attack of acute intermittent porphyria.
Further diagnostic tests of affected organs may be required, such as nerve conduction studies for neuropathy or an ultrasound of the liver. Basic biochemical tests may assist in identifying liver disease, hepatocellular carcinoma, and other organ problems.
Treatment
None; oral β-carotene may or may not control the skin manifestations but has no effect on porphyrin metabolism or the important systemic manifestations.
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