We report a 5-year-old boy presenting with multiple elastic type nevi and osteopoikilosis who was diagnosed as having Buschke-Ollendorff syndrome at an early age. Connective tissue lesions may present as the main symptom of varying clinical entities with different outcomes. Differential diagnosis includes papular elastorrhexis, fibroelastolytic papules of the neck, papular acne scars, and late onset focal dermal elastosis. Rare genodermatoses, i.e. Buschke-Ollendorff syndrome, pseudoxanthoma elasticum, juvenile hyaline fibromatosis and familiar cutaneous collagenoma should be carefully evaluated to provide appropriate genetic counseling and to avoid unnecessary treatment procedures.

High variability of the clinical appearance of malignant melanoma (MM) and its metastases render the differential diagnosis of solid amelanotic tumours difficult. We report a 71-year-old woman with several unusual cutaneous tumours of cerebriform morphology, suggesting skin metastases from occult internal cancer. Histopathological findings and thorough investigations, however, revealed a late-stage metastatic MM. We discuss the differential diagnosis of skin metastases of various origin and underline the difficulties for early detection of MM.

Experimental evidence is provided that selenomethionine oxide (MetSeO) is more readily reducible than its sulfur analogue, methionine sulfoxide (MetSO). Pulse radiolysis experiments reveal an efficient reaction of MetSeO with one-electron reductants, such as e(aq)-, (k = 1.2x10(10) M(-1) s(-1)), CO2*- (k = 5.9x10(8) M(-1) s(-1)) and (CH3)2 C*OH (k = 3.5x10(7) M(-1) s(-1)), forming an intermediate selenium-nitrogen coupled zwitterionic radical with the positive charge at an intramolecularly formed Se(three-electron bond)N 2sigma/1sigma* three-electron bond, which is characterized by an optical absorption with lambda(max) at 375 nm, and a half-life of about 70 micros. The same transient is generated upon HO* radical-induced one-electron oxidation of selenomethionine (MetSe). This radical thus constitutes the redox intermediate between the two oxidation states, MetSeO and MetSe. Time-resolved optical data further indicate sulfur-selenium interactions between the Se(three-electron bond)N transient and GSH. The Se(three-electron bond)N transient appears to play a key role in the reduction of selenomethionine oxide by glutathione.

Publisher Summary Selenoproteins carry out a variety of catalytic functions, many of which are redox reactions. A novel function for selenoproteins that has been reported is the reduction of peroxynitrite. Studies were prompted by the observation of a very efficient reduction of peroxynitrite by ebselen, exhibiting the highest second-order rate constant for a low-molecular-weight compound with peroxynitrite known so far, 2.0 x 106 M-lsec-1. In analogy to the reaction cycle for ebselen, Scheme 1A presents the proposed sequence. In the first step, the selenocysteine, probably as the selenolate, reacts with peroxynitrite to oxidize to the corresponding selenenic acid, yielding nitrite. However, peroxynitrous acid may also react to yield nitrous acid. The subsequent two steps in the reaction cycle are facile regeneration reactions at the expense of reducing equivalents provided by GSH in cells, known from the extensive work on GPx. Regarding the chemical mechanism, it might be concluded that the selenolate form of selenocysteine residue is required. However, a selenol moiety is not strictly necessary for peroxynitrite reductase activity, in contrast to the GSH peroxidase action, because the carboxymethylated selenium derivative maintained activity. This is in accord with the high rate constant obtained for 2-(methylseleno) benzanilide and for selenomethionine (Scheme 1B).