Skip areas of retained melanin: A clue to the histopathological diagnosis of idiopathic guttate hypomelanosis

Abstract

Biopsy findings in 55 cases of idiopathic guttate hypomelanosis (IGH) are reported. Most cases had a flat epidermis with loss of the rete pattern and a thickened orthokeratotic basket weave stratum corneum. The epidermis had markedly decreased to absent melanin in the basal layer and reduced numbers of melanocytes at the dermoepidermal junction. One-third of patients had a sparse perivascular lymphocytic infiltrate, whereas the rest had no significant dermal inflammation. These findings are in concordance with current literature. However, small foci of retained melanin in the basal layer (skip areas) alternating with larger areas of melanin loss were present in almost 80% of cases. This finding has not been reported earlier and appears to be quite specific to IGH and may be used as a clue to differentiate IGH from other similar conditions such as vitiligo and guttate morphea.

Do oxidative stress and melanin accumulation contribute to the pathogenesis of idiopathic guttate hypomelanosis: A prospective case‐control study

“…The marked reduction to absence of melanosomes, that too with predominance of immature melanosomes, has been observed not only in the lesional melanocytes, but also in keratinocytes of IGH lesions. Interestingly, although an absolute reduction in the number of melanocytes has been reported as a histopathological hallmark of IGH lesions, 10,15,16,18 it was not observed on histology of the specimens of our patients. Kakepis et al also did not observe absolute reduction in melanocyte number in their electron microscopy findings of IGH lesions 19 .…”

“…Features such as flat epidermis with effaced rete ridges, orthokeratotic basket-weave stratum corneum, and basal layer showing areas of markedly decreased to absent melanin with small skip areas of retained melanin interspersed with the alternating with large areas of melanin loss were considered diagnostic for IGH. 10 Other features such as reduction in the number of melanocytes, acanthosis, basal cell vacuolization, thick grenz zone resulting from papillary dermal sclerosis, mild perivascular inflammatory infiltrate, and solar elastosis were looked for, but not necessary for histological confirmation of diagnosis. Ten randomly selected specimens were stained with Masson-Fontana staining method to evaluate the distribution of melanin pigment deposits.…”

Melanocyte abnormalities and senescence in the pathogenesis of idiopathic guttate hypomelanosis

“…Joshi 2014 also reported in almost 80% of cases that small area of retained melanin in the basal layer of skin alternating with larger areas of melanin loss. This finding is quite specific for the IGH, and the condition is not similar to other hypopigmentary disorders such as vitiligo . Melanocytes from IGH patients were bigger in size and pigmented as compared to the control melanocytes.…”

“…This finding is quite specific for the IGH, and the condition is not similar to other hypopigmentary disorders such as vitiligo. 12 Melanocytes from IGH patients were bigger in size and pigmented as compared to the control melanocytes. Dendrites, which are responsible for the transfer of melanin pigment to the keratinocytes, were very small and retracted in IGH patients; on the other hand, the dendrites of control melanocytes were long and spreaded.…”

Clinicopathologic findings of guttate leukoderma in Darier disease: A helpful diagnostic feature

“…Distinction from IGH is supported by the epidermal changes observed; epidermal atrophy is typical of IGH. 9 Evidence of postinflammatory pigment alteration (pigment incontinence and melanophages) was absent. Taken together with the unique histologic findings, the historical and clinical findings of GL support this manifestation as a distinct clinicopathologic feature of DD.…”