Nevus psiloliparus: Newly described histopathological features from transverse sections

Abstract

Nevus psiloliparus is a rare fatty tissue nevus that is a marker for encephalocraniocutaneous lipomatosis, a neurocutaneous syndrome with ocular and central nervous system anomalies. Clinically, nevus psiloliparus is often described as a congenital alopecia and appears as an irregularly shaped, circumscribed area of alopecia on the scalp. Histopathology demonstrates a near‐complete absence of mature hair follicles with preservation of arrector pili muscles and mature adipocytes within the dermis. The pathogenesis of nevus psiloliparus may be related to mosaic mutations in fibroblast growth factor receptor 1. Herein we report the histopathological features of a nevus psiloliparus in an 11‐year‐old girl diagnosed from transverse sections, which show “shadow” follicular units characterized by columns of loosely arranged collagen and a relative paucity of elastic fibers.

Localized hair loss in infancy: a review

“…It presents as an irregularly shaped and well circumscribed area of alopecia with a soft, smooth surface that is either skin-colored or slightly yellow (Fig. 1d) [23]. Lesions are most commonly located on the frontal or frontoparietal region of the scalp.…”

“…Lesions are most commonly located on the frontal or frontoparietal region of the scalp. Histologically, lesions show an absence of mature hair follicles, preservation of arrector pili muscles, and abundant fatty tissue in the dermis [23]. While nevus psiloliparus can appear in isolation, it is the classic cutaneous sign of encephalocraniocutaneous lipomatosis (ECCL) [22,24,25].…”

“…ECCL is a rare neurocutaneous disorder characterized by CNS and ocular anomalies due to heterogeneous malformations of ectomesodermal tissues caused by a somatic autosomal mutation in the Ras-MAPK pathway [26]. Nevus psiloliparus is seen in 80% of affected children and is one of the main diagnostic criteria of ECCL [23]. Therefore, it is important for nevus psiloliparus to be correctly diagnosed in order for infants to receive the appropriate work-up for possible ECCL.…”

Encephalocraniocutaneous Lipomatosis

“…1,2 Nevus psiloliparus is confirmed by excisional biopsy with confirmatory histopathology showing increased lipomatous tissue, a lack of mature hair follicles, and orphaned erector pili. 5 However, NP is not specific to ECCL and may be found in other mosaic RASopathies. 1 In this report, we present a case of ECCL that was discovered after investigations into a possible NP and then briefly review the importance of multidisciplinary management in ECCL.…”

“…Nevus psiloliparus is an important dermatologic hallmark of ECCL found in 80% of ECCL patients and typically presents as an irregularly shaped, confined area of alopecia on the frontotemporal or zygomatic region of the scalp 1,2 . Nevus psiloliparus is confirmed by excisional biopsy with confirmatory histopathology showing increased lipomatous tissue, a lack of mature hair follicles, and orphaned erector pili 5 . However, NP is not specific to ECCL and may be found in other mosaic RASopathies 1 …”