Monarch Disease Ontology identifier MONDO_0100491 (generalized pustular psoriasis) is a rare and extreme form of psoriasis characterized by the appearance of sterile pustules which can take many patterns. All the main pathological features of the disease are accentuated. Generalized pustular psoriasis is clinically heterogeneous in its age at onset, precipitants, severity, and natural history. Many overlapping clinical entities are recognized. There is a relationship between these entities and plaque psoriasis, as some individuals may have episodes of plaque psoriasis preceding or following the generalized pustular psoriasis, but in others generalized pustular psoriasis occurs as the sole phenotype without plaque psoriasis at any time.