A recent clinical problem-solving case (TW Fredrick et al. NEJM 2021; 385; 549-554. Turning Purple with Pain) is a good review on episodic pain and acute intermittent porphyria (AIP).

The case presentation regarded a 32 yo with episodic severe pain for 10 years (associated with constipation) that required morphine. Episodes occurred every month or two and lasted for several days. Some clues in this case included the development of hyponatremia, purple urine, and an episode in which she was “out of it.” This episode was attributed to opioid use and providers were concerned about opioid-seeking behavior and a conversion disorder.

She had extensive evaluations including imaging, panendoscopy, and labs. Atypical labs included serum tryptase, cortisol, and C1 esterase inhibitor level. Ultimately, her constellation of findings led to a urine porphyrin levels which disclosed elevated porphobilinogen (PBG) and delta-aminolevulinic acid. The diagnosis of AIP was confirmed with genetic testing.

Key points:

• AIP results from mutations in HMBS, the gene encoding hydroxymethylbilane synthase which plays an integral role in heme synthesis
• AIP is rare, affecting about 5 people per million; age of onset is typically 18-45 years of age
• In a case series, 18% of patients with AIP reported nearly constant abdominal pain symptoms, 73% had nausea/vomiting, 60% have constipation, and 55% had anxiety/depression.
• Associated conditions included hypertension ((43%), peripheral neuropathy (43%), chronic kidney disease (29%), psychiatric disorders (22%), palpitations (19%), seizures (9%), cirrhosis (2%), and hepatocellular carcinoma (1%)
• Flares of AIP may be triggered by alcohol, infections, low caloric intake, and medications (especially seizure medications and hormonal contraceptives)
• The urine can appear red or brown and darkens on exposure to oxygen, light or heat. Purple urine reflects very high urinary PBG levels

My take: This article provides a useful overview. AIP needs to be considered in adolescents with severe abdominal pain that results in hospitalization (especially if episodic).

Related blog post: Liver Shorts -June 2020 (with AIP article)

Also, data supporting COVID-19 effectiveness in reducing the risk of hospitalization–CDC study shows unvaccinated people are 29 times more likely to be hospitalized with Covid (CNBC)