Persistent pigmented purpuric dermatitis: granulomatous variant.

The persistent pigmented purpuric dermatitides (PPPD) are a spectrum of dermatologic disorders characterized by petechial and pigmented macules usually confined to the lower limbs. Their etiology is unknown and several clinical variants are recognized. At the microscopic level they are characterized by angiocentric lymphocytic inflammation, red blood cell extravasation and hemosiderin deposition. A granulomatous variant of the PPPD has recently been described and to date eleven cases have been reported in the literature. In contrast to the conventional type, this variant is characterized histopathologically by ill-defined, non-necrotizing granulomata admixed with the lymphocytic inflammatory background. Although initially the granulomatous variant of the PPPD was thought to occur only in Asian patients, this sole racial predilection has not been substantiated. A tenuous association with hyperlipidemia has been noted but this requires further study. The principal importance of recognizing this entity lies in the need to include it in the histopathological differential diagnosis of granulomatous dermal infiltrates. We report here an additional patient with the granulomatous variant of PPPD and elaborate on this entity in the context of existing information in the literature.

Eukaryotic evolution: early origin of canonical introns.

Spliceosomal introns, one of the hallmarks of eukaryotic genomes, were thought to have originated late in evolution and were assumed not to exist in eukaryotes that diverged early -- until the discovery of a single intron with an aberrant splice boundary in the primitive 'protozoan' Giardia. Here we describe introns from a close relative of Giardia, Carpediemonas membranifera, that have boundary sequences of the normal eukaryotic type, indicating that canonical introns are likely to have arisen very early in eukaryotic evolution.