Acral peeling in Nagashima type palmo-plantar keratosis patients reveals the role of serine protease inhibitor B 7 in keratinocyte adhesion.

Acral peeling skin syndrome (APSS) is a heterogenous group of genodermatoses, manifested by peeling of palmo-plantar skin and occasionally associated with erythema and epidermal thickening. A subset of APSS is caused by mutations in protease inhibitor encoding genes, resulting in unopposed protease activity and desmosomal degradation and/or mis-localization, leading to enhanced epidermal desquamation. We investigated two Arab-Muslim siblings with mild keratoderma and prominent APSS since infancy. Genetic analysis disclosed a homozygous mutation in SERPINB7, c.796C > T, which is the founder mutation in Nagashima type palmo-plantar keratosis (NPPK). Although not previously formally reported, APSS was found in other patients with NPPK. We hypothesized that loss of SERPINB7 function might contribute to the peeling phenotype through impairment of keratinocyte adhesion, similar to other protease inhibitor mutations that cause APSS. Mis-localization of desmosomal components was observed in a patient plantar biopsy compared with a biopsy from an age- and gender-matched healthy control. Silencing of SERPINB7 in normal human epidermal keratinocytes led to increased cell sheet fragmentation upon mechanical stress. Immunostaining showed reduced expression of desmoglein 1 and desmocollin 1. This study shows that in addition to stratum corneum perturbation, loss of SERPINB7 disrupts desmosomal components, which could lead to desquamation, manifested by skin peeling.

An unusual co-occurrence of Langerhans cell histiocytosis and Rosai-Dorfman disease: report of a case and review of the literature.

BACKGROUND: The co-occurrence of Langerhans cell histiocytosis (LCH; disorder characterized by proliferation of Langerhans cells) and Rosai-Dorfman disease (RDD; histiocytic entity that is one of the non-Langerhans cell diseases) is extremely rare and raises several questions regarding the nature of the diseases. METHODS: We describe a 10-year-old boy who presented with a 3-month history of right scalp swelling. Clinical, pathological, and imaging evaluation disclosed multiple LCH of bone and cutaneous RDD. RESULTS: After initiating prednisone and vinblastine therapy, the patient developed an asymptomatic diffuse papular eruption. Biopsy revealed cutaneous RDD. Treatment was continued with a good response of bone LCH and significant amelioration of the cutaneous findings. CONCLUSIONS: Co-occurrence of LCH and RDD is a rare phenomenon. Various explanations, including the role of chemotherapy, are suggested based on our and several previously reported cases.