Psoriatic lesions affecting the scalp, nails, palms, and the soles of the feet are described as difficult-to-treat psoriasis and require specific management. Involvement of these sites often has a significant physical and emotional impact on the patient and the lesions are difficult to control with topical treatments owing to inadequate penetration of active ingredients and the poor cosmetic characteristics of the vehicles used. Consequently, when difficult-to-treat sites are involved, psoriasis can be considered severe even though the lesions are not extensive. Scant information is available about the use of biologic therapy in this setting, and published data generally comes from clinical trials of patients who also had moderate to severe extensive lesions or from small case series and isolated case reports. In this article we review the quality of the scientific evidence for the 4 biologic agents currently available in Spain (infliximab, etanercept, adalimumab, and ustekinumab) and report level i evidence for the use of biologics to treat nail psoriasis (level of recommendation A) and a somewhat lower level of evidence in the case of scalp involvement and palmoplantar psoriasis.

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Squamous metaplasia in the skin has been reported in the eccrine ducts as eccrine squamous syringometaplasia (ESS). To our knowledge, squamous metaplasia of sebaceous gland (SMSG) has not been described in human skin. Twenty-two biopsy specimens from patients with pressure lesions after cardiac surgery with extracorporeal circulation were evaluated for the presence of SMSG. Squamous metaplasia of sebaceous gland was identified in five of the eight scalp biopsies and none of the buttock biopsies. The squamous metaplasia began in the germinative outer layer and advanced in a centripetal way. We believe that SMSG is an unspecific change of the sebaceous cells secondary to a chronic injury. Ischemia appears to play a mayor role, but other factors such as chronic trauma or toxicosis can not be ruled out.