Fig. 29.1
Upper panel demonstrates a young woman with progressive macular hypomelanosis. Note the multiple smooth hypopigmented macules. Lower panel demonstrated an African–American woman with extensive minimally finely scaly hypopigmented macules of mycosis fungoides
Case
A patient presents with a diffuse eruption consisting of multiple hypopigmented macules.
A solitary hypopigmented patch often represents nevus hypopigmentosus or depigmentosus, or nevus anemicus (which is not truly hypopigmented but instead pale due to vasoconstriction). Occasionally, intradermal or intra-articular steroid injection may result in hypopigmentation without appreciable atrophy. These disorders will not be addressed here.
Clinical differential diagnosis includes
It is important to note that lesions of LS are not truly hypopigmented, but appear whitish secondary to the aberrant physical properties of the abnormal papillary dermis, just as lesions of atrophoderma appear brownish without having increased pigmentation.
pityriasis alba (P. Alba)
mycosis fungoides (MF)
sarcoidosis
early vitiligo
progressive macular hypomelanosis (PMH)
tinea versicolor (TV), and
lichen sclerosis (LS).
These disorders vary in their pathophysiology from mild inflammation (P. Alba) to autoimmune (vitiligo) to lymphoma (MF) and a granulomatous disorder (sarcoidosis).
Clinical Clues
Clinical clues are moderately helpful in the differential diagnosis.
Morphological Clues
All disorders in this group present with lesions that are well defined, except P. Alba and PMH, in which lesions are ill-defined. Although all the above disorders appear macular, some lesions of LS and sarcoidosis may be palpable.
Early vitiligo is strongly favored if some of the lesions are depigmented or if mucous membranes are involved.
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