Two public figures in the United States have separately disclosed diagnoses of rare conditions that produce abrupt, disorienting symptoms, drawing fresh attention to disorders that often elude initial detection. On 27 June, journalist Katie Couric experienced a transient global amnesia (TGA) episode during a festival in Colorado, leaving her unable to recall the year, the sitting president, or the events of several hours. Days later, technology entrepreneur and biohacker Bryan Johnson announced he has autoimmune gastritis (AIG), a chronic condition in which the immune system attacks stomach lining cells, impairing nutrient absorption and, in some patients, triggering severe brain fog. Both conditions are uncommon: TGA strikes an estimated 3 to 10 people per 100,000 annually, with incidence rising to roughly 23 to 32 per 100,000 among those over 50, while AIG is a lifelong autoimmune disorder often diagnosed only after years of unexplained iron or B12 deficiency.

TGA manifests as a sudden, temporary inability to form new memories, sometimes erasing recent recollections, yet patients retain self-awareness and identity. Couric’s episode resolved within hours, and neuroimaging ruled out stroke. The precise mechanism remains uncertain, though specialists point to transient dysfunction in the hippocampus, possibly triggered by brief interruptions in blood or oxygen flow, emotional stress, or temperature extremes. The condition leaves a permanent memory gap for the duration of the episode, and recurrence is estimated at around 15 per cent over a decade. Viewed from a clinical perspective, TGA is a diagnosis of exclusion, requiring rapid stroke workup to rule out more dangerous causes.

Johnson’s AIG, by contrast, is a progressive condition that can smoulder for years before diagnosis. The immune system destroys parietal cells, reducing stomach acid and hampering absorption of iron, vitamin B12, and other micronutrients. Johnson, 48, linked his diagnosis to years of poor diet and chronic stress before he adopted an extreme health regimen. Lori Taylor, a 60-year-old dietitian with the same condition, described to Business Insider a years-long decline marked by hair loss, exhaustion, and cognitive lapses so severe she could not read her own handwriting. Diagnosis often requires detection of parietal cell antibodies and endoscopic confirmation of gastric inflammation. Treatment focuses on supplementation and, in some cases, betaine hydrochloride to temporarily raise stomach acid, though clinical evidence for this approach remains limited.

These contemporary cases echo a far more baffling episode from 1994, revisited this month by Argentine newspaper Clarín. Gloria Ramírez, a 31-year-old woman with advanced cervical cancer, arrived at a California emergency department with nausea and chest pain. As staff drew her blood, they noticed an oily sheen on her skin and a garlic-fruit odour; within minutes, 23 of 37 health workers fell ill, with several losing consciousness. Ramírez died of cardiac arrhythmia, but extensive post-mortem toxicological and environmental testing found no chemical agent, and the event remains unexplained. The case, which forced the evacuation of the emergency department, illustrates how even modern medicine can be confounded by rare physiological presentations.

For patients, the immediate milestone is management: Couric has been advised that TGA is typically a one-time event, while Johnson and others with AIG face lifelong monitoring of vitamin levels and potential complications such as pernicious anaemia. Researchers continue to investigate the triggers of TGA and the autoimmune pathways in AIG, but no definitive preventive measures exist. The next factual marker for both conditions will be long-term follow-up data on recurrence and progression, as well as any insights from patient registries that might clarify why some individuals develop these disorders while others do not.