In the acute attack the neurological dysfunction can involve any portion of the nervous system. It is believed that an imbalance in the autonomic innervation of the gut leads to abdominal pain which is commonly associated with the attack. If peripheral neuropathy, such as pain in the back and legs or parathesias occurs it is almost always preceded by abdominal pain. Complete flaccid paralysis can develop over a few days. Other autonomic neuropathies that may be seen are sweating, vascular spasm, labile hypertension, and sinus tachycardia. A grave sign is the development of respiratory paralysis and in very severe attacks patients are unable to speak, breathe, or swallow. Central nervous dysfunction can be seen as well with hallucinations, seizures, coma, bulbar paralysis, hypothalamic dysfunction, or cerebellar and basal ganglion involvement.
A severe hyponatremia can develop from inappropriate release of antidiuretic hormone, gastrointestinal loss and possibly renal loss. Other associated problems in some patients may be seen with increased serum binding globulin, increased cholesterol, and increased amylase.
Laboratory findings. The defect in porphobilinogen deaminase causes a build up of ALA and porphobilinogen (PBG) which causes their increased secretion in the urine. Attacks of neurological dysfunction is associated with increased levels of ALA and PBG excretion in the urine with the levels dropping as the patients condition improves. At the time of the acute attack, screening tests like the Hoesch or Watson-Schwartz test for the detection of PBG in urine. A positive screening test should always be confirmed by a quantitative test for PBG in the urine. To discriminate acute intermittent porphyria from variegate porphyria and hereditary coproporphyria which also can have increased PBG in the urine, a specific test for erythrocyte PBG deaminase activity is required.
Treatment. Patients should be instructed on the precipitating factors to avoid. A high carbohydrate diet (greater than 400 g/day) can cause a decrease of porphyrin precursor excretion and results in clinical improvement in some cases. For the abdomnial pain phenothiazines can be used for control with merperidine use if necessary. Autonomic manifestations such as hypertension and tachycardia have been controlled with the use of propanolol. In patients who do not have coagulopathies or are not on anticoagulant therapy the use of hematin can be considered. If started early in the attack it may have benefit through the lowering of porphyrin precursor excretion. Since nerve regeneration is the rat-limiting factor to improvement of established neuropathy, hematin will have no effect on recovery.
