What is the term for a rash with an irregular shape?

From the Guidelines

The term for a rash with an irregular shape is best described as having "irregular borders" as stated in the criteria for diagnosing cutaneous melanoma 1. This description is part of the clinical criteria suggestive of malignancy in a pigmented cutaneous lesion. The criteria include:

• Asymmetry
• Irregular borders
• Heterogeneous color
• Large diameter
• Evolution (recent change), which must co-exist with at least one of the preceding criteria. In the context of skin lesions, an irregular shape or border can be an important diagnostic feature for various conditions, including cutaneous melanoma, as discussed in the study from the British Journal of Cancer 1. Another study from the British Journal of Dermatology 1 describes Bowen's disease as presenting with a gradually enlarging, well-demarcated erythematous plaque with an irregular border and surface crusting or scaling, further highlighting the importance of irregular borders in dermatological diagnoses. When examining a rash with an irregular shape, healthcare providers should consider the distribution pattern, associated symptoms, and the patient's medical history to determine the underlying cause, as the irregularity in shape can reflect the underlying pathophysiological process.

From the Research

Rash Description Terms for Irregular Shapes

• The terms used to describe irregularly shaped rashes include:
  • Annular: ring-shaped 2
  • Arciform: arc-shaped 2
  • Polycyclic: having multiple cycles or rings 2
  • Nummular: coin-shaped 2
  • Linear: having a linear or straight shape 3, 4

Characteristics of Irregularly Shaped Rashes

• Irregularly shaped rashes can have various characteristics, such as:
  • Evolving shapes: rashes can change shape over time, for example, from arciform to annular to polycyclic 2
  • Multiple configurations: a single disease can present in multiple shapes, such as annular, arciform, or polycyclic 2
  • Variable sizes: rashes can vary in size, from small to large 5

Examples of Irregularly Shaped Rashes

• Examples of diseases that can present with irregularly shaped rashes include:
  • Psoriasis: can present with circular plaques 5
  • Linear morphea: a variant of scleroderma that presents with linear lesions 3
  • Mycosis fungoides: a type of cutaneous T-cell lymphoma that can present with various shapes, including linear 4