Acute Intermittent Porphyria (AIP). Porphobilinogen (PBG) deaminase deficiency.
Incidence
AD disease. Occur 5-10/100.000. The gene is located in chromosome 11. Hundreds of patients have been reported, but less than 50 children.
Clinical Characteristics
Acute intermittent attacks of abdominal pain, psychic disturbances and polyneuropathy. Attacks are often triggered by barbiturates and other drugs. Most pts (90%) with enzyme deficiency remain normal. Usually start after age 20 yrs, but 15% may occur before 20 yrs. Can be seen in pediatric age. Abdominal pain is usually the first symptom, frequently associated with vomiting. Diarrhea may occur. It may look as an acute abdomen. Pts may have urinary retention, hypertension, tachycardia, occasionally fever. Psychiatric symptoms such as restlesness, insomnia, confusional psychosis, hallucinations, violent behavior may occur pre or post polyneuropathy. Seizures may occur also. Polyneuropathy is mainly motor, usually distal. Sensory findings are often also present, with limb pain. Absent DTRs noted. The polyneuropathy usually stay on the limbs may may spread. affecting respiration and cranial nerves with dysphagia. Rarely eye muscles are affected. CSF protein remain normal usually. EMG denervation features and slow NCV are usual. Urine shows a red discoloration due to incresed urinary excretion of porphyrins. Polyneuropathy usually recover after several weeks.
Precipitants
Barbiturates, antiepileptic drugs, sulfas, ergotamine, chloroquine and other drugs may trigger an attack.
Provocation Tests
Not recommended.
Diagnostic Procedures
EB-RBC. EB-F, EB-W. Increased amounts in urine of delta-aminolevulinic acid (ALA) and porphobilinogen (PBG) during and between attacks. Hypercholesterolemia. High beta-lipoproteins.