From the Guidelines
Macules and patches are flat skin lesions that differ primarily in size, with a macule being a small, flat, discolored area of skin less than 1 cm in diameter, and a patch being a larger macule measuring more than 1 cm across. These lesions can result from various causes including sun exposure, genetic factors, inflammatory conditions, or vascular abnormalities 1.
Key Characteristics
- Macules are non-palpable, meaning they cannot be felt when running your finger over them, and they represent changes in skin color without any elevation or depression of the skin surface.
- Patches are also non-palpable and represent larger changes in skin color.
- Common examples of macules include freckles, flat moles, and petechiae (tiny red spots due to bleeding under the skin), while patches include vitiligo (white patches due to loss of pigment), port-wine stains, and large flat birthmarks.
Causes and Associations
- Cutaneous mastocytosis in children can present with macules and patches, with the most common form being urticaria pigmentosa (UP), which represents 70–90% of the cases 1.
- Infantile hemangiomas can also present as macular or telangiectatic patches, and may be classified as superficial, deep, or mixed, and as focal, multifocal, or segmental 1.
- Immune-related adverse events in patients treated with immune checkpoint inhibitor therapy can also cause cutaneous toxicities, including rash, pruritis, and vitiligo, which can present as macules and patches 1.
Management
- Treatment of macules and patches depends entirely on the underlying cause and may include topical medications, laser therapy, or simply monitoring if the lesion is benign.
- It is essential to have any new, changing, or concerning skin lesions evaluated by a healthcare provider to determine their nature and appropriate management.
From the FDA Drug Label
CLINICAL PHARMACOLOGY Topical application of hydroquinone produces a reversible depigmentation of the skin by inhibition of the enzymatic oxidation of tyrosine to 3,4-dihydroxyphenylalanine (dopa) (Denton, C. et al., 1952)1 and suppression of other melanocyte metabolic processes (Jimbow, K. et al., 1974)2. Exposure to sunlight or ultraviolet light will cause repigmentation of bleached areas (Parrish, J.A. et al., 1978)3. The FDA drug label does not answer the question.
From the Research
Definition of Macules and Patches
- A macule is a small, flat lesion with a distinct color, typically less than 0.5 cm in size 2.
- A patch is a larger lesion with a distinct color, typically greater than 0.5 cm in size 2.
Hyperpigmentation and Macules
- Hyperpigmentation is a broad term that describes increased pigmentation in the skin, and macules can be a manifestation of hyperpigmentation 3.
- Hyperpigmentation can be caused by various factors, including hormonal changes, ultraviolet radiation, and inflammation 3.
Treatment of Hyperpigmentation
- Topical hydroquinone is a commonly used treatment for hyperpigmentation, but it has been associated with side effects such as cancer risk and exogenous ochronosis 4, 5.
- Alternative treatments for hyperpigmentation include laser toning, chemical peels, and topical agents such as thiamidol, Polypodium leucotomos, and glutathione 4, 3.