Report from Mongolia – How much do we know about the incidence of rare cases in less developed countries: a case series

INTRODUCTION: Case reports are important instruments to describe rare disease conditions and give a rough estimation of their global incidence. Even though collected in international databases, most case reports are published by clinicians from industrialized nations and little is known about the incidence of rare cases in less developed countries, which are home to 75% of the world's population. CASE PRESENTATION: We present seven patients who suffered from diseases which are either considered to be rare or have not yet been described before according to international databases, but occurred during a 5-month period in one intensive care unit of a less developed country. During the observation period, patients with a spontaneous infratentorial subdural hematoma (Asian, female, 41 years), general exanthema and acute renal failure after diesel ingestion (Asian, male, 30 years), transient cortical blindness complicating hepatic encephalopathy (Asian, female, 49 years), Fournier gangrene complicating acute necrotizing pancreatitis (Asian, male, 37 years), acute renal failure due to acetic acid intoxication (Asian, male, 42 years), haemolytic uremic syndrome following septic abortion (Asian, female, 45 years), and a metal needle as an unusual cause of chest pain (Asian, male, 41 years) were treated. According to the current literature, all seven disease conditions are considered either rare or have so far not yet been reported. CONCLUSION: The global incidence of rare cases may be underestimated by contemporary international databases. Diseases which are currently considered to be rare in industrialized nations may occur at a higher frequency in less developed countries. Reasons may not only be a geographically different burden of certain diseases, limited diagnostic and therapeutic facilities, but also a relevant publication bias.