Peeling Skin Syndrome 5 (PSS5) is a genodermatosis characterized by superficial, painless peeling of the skin. Affected areas include the dorsal and palmar surfaces of the hands and feet, as well as the fore-arms and legs. Peeling is usually seen to be exacerbated by external factors such as heat, humidity or friction. Other symptoms include underlying erythema and diffuse yellowish hyperkeratotic palmoplantar plaques. Skin biopsies may reveal acanthosis, hyperkeratosis, disadhesion of keratinocytes in basal and suprabasal layers of epidermis and widening of intercellular spaces.
The condition has an onset at around 3 to 6 months of age. While PSS is an uncommon disorder, with less than 100 cases reported worldwide, PSS5 is a rare subset of PSS, with only about 3 reported incidences. Diagnosis of PSS5 is based on clinical features and genetic analysis of the SERPINB8 gene. Treatment is limited to the use of emollient ointments to provide relief.
PSS5 follows an autosomal recessive pattern of inheritance and is caused by mutations in the SERPINB8 gene. This gene encodes a high molecular weight serine protease inhibitor and its absence in keratinocytes has been shown to result in a cell-cell adhesion defect, which is heightened by mechanical stress. So far only 3 mutations in the SERPINB8 gene have been associated with PSS5.
Pigors et al. (2016) studied Exfoliative Ichthyosis patients and identified their underlying gene mutations. The authors described a 5-year-old boy and his 3-year-old sister from a consanguineous Tunisian family exhibiting superficial peeling of small areas of the palmar and dorsal faces of the hands and feet, with an underlying erythema. The peeling was painless and easily removed, and was seen to be exacerbated by heat, humidity and friction. A female patient from UAE suffered similar symptoms, but with peeling extending to her lower arms. Homozygosity mapping and WES of the Tunisian patients helped identify a novel homozygous c.947delA (p.Lys316Serfs*90) mutation in exon 7 of the SERPINB8 gene. The variant was predicted to lead to the loss of the reactive site loop of SERPINB8, crucial for forming the SERPINB8-protease complex. Furthermore, a homozygous missense mutation c.2T>C (p.Met1?) was detected in exon 2 of the SERPINB8 gene from the UAE patient. It was predicted to result in an N-terminal truncated protein.
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