The term "parapsoriasis" is confusing and requires explanation. It encompasses a number of different pathologic states clinically manifested by chronic recalcitrant erythematous scaling lesions.
About 100 years ago, Unna et al. (1) described two cases of the so-called parakeratosis variegata. Brocq (2), some years later, saw one of Unna and colleagues' cases, as well as some similar cases, and described it as "erythrodermies pityriasiques en plaques desseminees.''
Brocq (1856-1928) in his article in 1902 reviewed the American, French, and German cases and reported 10 cases of his own (3). He coined the term "parapsoriasis" because of the similarities of the disease to psoriasis, seborrhoic eczema, and lichen ("paralichen").
The common features of the subgroups described by Brocq are: (i) long duration of the disease; (ii) good general health; (iii) absence of itching; (iv) erythema and pityriasiform scaling; (v) control of disease without cure by topical treatment; and (vi) round cell infiltrate in the papillary dermis.
The three conditions depicted in Brocq's scheme (Fig. 1) are:
1. ''Parapsoriasis en gouttes'' (guttate parapsoriasis). Today, this disease usually is referred to as pityriasis lichenoides chronica or as parapsoriasis guttata of Jadassohn and Juliusberg. It resembles papular syphilis or guttate psoriasis. Nosologically, it is completely unrelated to mycosis fungoides even though otherwise stated by some authors (4). Pityriasis lichenoides et varioliformis acuta (Mucha-Habermann's disease) is an acute variant of this form, which has to be differentiated from lymphoma-toid papulosis. These diseases—except lymphomatoid papulosis—are not related to mycosis fungoides or other CTCLs.
2. ''Parapsoriasis lichenoide,'' featuring a network of ''pseudopapular'' lesions with atrophy exhibiting a poikilodermatous appearance and the cases of parakeratosis variegata, described by Unna (1) and poikilodermia vasculare atrophicans (Jacobi) are most likely variants of the inflammatory form of parapsoriasis en plaques.
3. ''Parapsoriasis en plaques'' (Brocq's disease), characterized by round or oval well-circumscribed macules (''plaques'' in the French terminology), is usually 2-6 cm in diameter.
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Do You Suffer From the Itching and Scaling of Psoriasis? Or the Chronic Agony of Psoriatic Arthritis? If so you are not ALONE! A whopping three percent of the world’s populations suffer from either condition! An incredible 56 million working hours are lost every year by psoriasis sufferers according to the National Psoriasis Foundation.