Papule (papula; synonym: nodule; ICD-10 R21: rash and other nonspecific skin eruptions) in dermatology refers to a nodule-like change on skin or mucosa (thickening of the skin). The diameter of the individual nodule is less than 5 mm.
The thickening of the skin appears as a solid elevation of the skin:
- Papule: circumscribed elevation of the skin < 1.0 cm in diameter.
- Plaques: areal increase > 1.0 cm in diameter
- Nodus (node): circumscribed in or above the skin protruding tissue consolidation > 1.0 cm
The papule belongs to the so-called primary efflorescences. These are skin changes that are the direct result of a disease.
Papules can be a symptom of many diseases (see under “Differential diagnoses”).
The following forms can be distinguished depending on the localization of the papules in the skin layers:
- Epidermal papules – the nodules occur in the stratum corneum (horny cell layer) or stratum spinosum (prickle cell layer) of the epidermis (epidermis); e.g. warts.
- Cutaneous papules – the nodules occur in the corium (dermis); e.g., in the context of a syphillis disease
- Epidermo-cutaneous papules – the nodules occur in the stratum corneum or stratum spinosum of the epidermis as well as in the corium (mixed form)
Course and prognosis: papules may regress completely, without leaving scars, spontaneously (by itself). If this is not the case and they are considered bothersome, it requires presentation to a dermatologist. If the papules are caused by a disease, the treatment of the disease is in the foreground. The course of papules depends on the skin layer from which the papules originate and their coloration, as well as the underlying disease.
