List of syndromes and diseases with unknown etiologies

International Statistical Classification of Diseases and Related Health Problems recognized

 * Pityriasis rosea 696.3
 * Metabolic syndrome 277.7
 * Irritable bowel syndrome 564.1
 * Alzheimer's disease 331.0
 * Fibromyalgia 729.1
 * Chronic fatigue syndrome 780.71
 * Balanitis xerotica obliterans
 * Anaphylactoid purpura

International Statistical Classification of Diseases and Related Health Problems unrecognized

 * Syndrome X
 * Sick building syndrome
 * Gulf War syndrome
 * Multiple chemical sensitivity