Hypopigmented rashes




8: Hypopigmented rashes


Abstract:



Disorders of skin pigmentation include those that make the skin lighter (hypopigmented). Appropriately recognizing disorders of hypopigmentation is important because many people assume that their skin will entirely depigment. Prompt diagnosis and treatment can assuage worries and improve outcomes. This chapter includes discussions of pityriasis alba, vitiligo, idiopathic guttate hypomelanosis, progressive macular hypopigmentation, and nevus anemicus.

Key terms:


pityriasis alba


vitiligo


idiopathic guttate hypomelanosis


progressive macular hypopigmentation


nevus depigmentosus


nevus anemicus



Pityriasis alba


Elizabeth Dupuy and Preeti Jhorar


Clinical features


Pityriasis alba is a benign inflammatory skin condition that presents with poorly circumscribed hypopigmented oval or round macules, patches, or thin plaques.



Differential diagnosis


The important differential diagnoses include vitiligo, tinea versicolor, seborrheic dermatitis, nevus depigmentosus, nevus anemicus, postinflammatory hypopigmentation, mycosis fungoides, leprosy, and ash-leaf spots of tuberous sclerosis.


Vitiligo


Vitiligo is well demarcated, with a chalky-white appearance and no skin surface change, such as scale. Vitiligo is completely depigmented, whereas pityriasis alba is hypopigmented.


Tinea versicolor


A KOH preparation will reveal hyphae and spores in the case of tinea versicolor. It is commonly located on the upper chest and back, unlike pityriasis alba, which almost exclusively affects the cheeks.


Seborrheic dermatitis


Especially in patients with darker skin tones, seborrheic dermatitis can present with hypopigmented macules or patches along the eyebrows, nasolabial folds, frontal hair line, and retroauricular skin. It may be associated with a greasy scale or scalp dandruff.


Nevus depigmentosus


Nevus depigmentosus is a congenital disorder of hypopigmentation that is present at birth or noticed shortly thereafter. It has an asymmetric distribution and is stable over time.


Nevus anemicus


Nevus anemicus is noticed at birth or in early childhood and presents as an irregular, hypopigmented patch. It is not truly a pigmentary disorder but is instead caused by vascular hypersensitivity that leads to vasoconstriction. It is typically a focal lesion. Pressing a glass slide onto the border of nevus anemicus will cause the hypopigmentation to expand out as the periphery blanches.


Postinflammatory hypopigmentation


Postinflammatory hypopigmentation can result from any inflammatory process on the skin, but there usually is a history of preceding rash.


Mycosis fungoides


Mycosis fungoides involves multiple hypopigmented macules, usually in photoprotected areas. Referral to dermatology should be considered if there is a more extensive distribution of pityriasis alba-like lesions, especially in darker skin patients.


Leprosy


Leprosy presents with hypoesthetic patches and can be considered with appropriate clinical history and geographic risk factor.


Ash-leaf spots of tuberous sclerosis


In tuberous sclerosis, lesions are typically present at birth, can be tear-drop or ash-leaf shaped, and accentuate with a Wood lamp examination. In older patients, lesions can be associated with other features of tuberous sclerosis, such as facial angiofibromas.


Referral to dermatology should be considered when there are doubts as to the diagnosis or if the clinical course is atypical.


Work-up




Initial steps in management




Warning signs/common pitfalls


Pityriasis alba is included in the differential diagnosis of hypopigmented or depigmented patches. Patients and sometimes physicians may be concerned that these lesions represent a more ominous depigmenting condition or an infectious process.


Counseling


The white spots on your skin are caused by a condition called “pityriasis alba.” This is not an infection, and it is not contagious. The cause of this condition is unknown; however, some believe it is a feature of atopic dermatitis or eczema. This condition will improve over a period of a few months to years and gradually the skin will return to normal pigmentation. Treatment is not necessary but if your skin is itchy, or if you desire treatment, we can try to use a low-potency topical steroid. Topical steroids should not be used for extended periods of time because their use may lead to side effects, such as thinning of the skin. An alternative treatment is a nonsteroidal antiinflammatory called a “topical calcineurin inhibitor,” such as tacrolimus ointment or pimecrolimus cream. Although these are labeled with an FDA black box warning regarding a theoretical increase in risk for lymphoma, most dermatologists believe they are safe to use, and studies have not shown any increased risk for cancer with topical use. Other interventions that may improve the appearance of skin are the use of sun protection and moisturizers.


Vitiligo


Regina Liu, Amy R. Vandiver, and Preeti Jhorar


Vitiligo is a common acquired disorder of pigmentation that results from the loss of functional melanocytes.


Epidemiology


Vitiligo affects approximately 0.5% to 2% of the population worldwide. The peak incidence is in the 10- to 30-year-old age group with an average age of onset of approximately 20 years, although it can manifest any time from shortly after birth to late adulthood.


Clinical features




Jul 22, 2021 | Posted by in Dermatology | Comments Off on Hypopigmented rashes
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