Atypical pityriasis rosea or psoriasis guttata? Early examination is the key to a correct diagnosis

Linear patterns of the skin and their dermatoses

Knowledge about the linear patterns of the skin is a key competence of dermatologists. Four major groups of linear patterns can be distinguished: Langer lines, dermatomes, Blaschko lines and exogenous patterns. Langer lines run in the direction of the underlying collagen fibers (least skin tension) and play an important diagnostic role for some exanthematous skin diseases. In the thoracodorsal region, the distribution of the Langer lines gives rise to what is referred to as a 'Christmas tree pattern'. A dermatome is an area of skin that is supplied by a single spinal nerve. Disorders with a neuronal origin follow this pattern of distribution. The lines of Blaschko delineate the lines of migration of epidermal cells during embryogenesis. Exogenous linear patterns are caused by external factors. The present CME article will highlight important skin disorders that primarily present in the form of one of the aforementioned patterns. In addition, we will also address skin conditions that may secondarily follow with these patterns (or distinctly not do so) as the result of various mechanisms such as the Koebner phenomenon, reverse Koebner phenomenon, and Wolf's isotopic response.

Topographic Differential Diagnosis of Chronic Plaque Psoriasis: Challenges and Tricks

BACKGROUND

Psoriasis is an inflammatory skin disease presenting with erythematous and desquamative plaques with sharply demarcated margins, usually localized on extensor surface areas.

OBJECTIVE

To describe the common differential diagnosis of plaque psoriasis classified according to its topography in the scalp, trunk, extremities, folds (i.e., inverse), genital, palmoplantar, nail, and erythrodermic psoriasis.

METHODS

A narrative review based on an electronic database was performed including reviews and original articles published until 1 September 2020, assessing the clinical presentations and differential diagnosis for psoriasis.

RESULTS

Several differential diagnoses could be considered with other inflammatory, infectious, and/or neoplastic disorders. Topographical differential diagnosis may include seborrheic dermatitis, tinea capitis, lichen planopilaris in the scalp; lupus erythematosus, dermatomyositis, cutaneous T-cell lymphomas, atopic dermatitis, syphilis, tinea corporis, pityriasis rubra pilaris in the trunk and arms; infectious intertrigo in the inguinal and intergluteal folds and eczema and palmoplantar keratoderma in the palms and soles.

CONCLUSIONS

Diagnosis of psoriasis is usually straightforward but may at times be difficult and challenging. Skin cultures for dermatophytes and/or skin biopsy for histological examination could be required for diagnostic confirmation of plaque psoriasis.

Clinical variants of pityriasis rosea

Pityriasis rosea (PR) is a common erythemato-squamous dermatosis which almost always, is easily diagnosed. Mostly the disease presents in its classical form. However, clinical dermatology is all about variations and PR is not an exception. Variants of the disease in some cases may be troublesome to diagnose and confuse clinicians. Prompt diagnosis and treatment of the condition becomes necessary to avoid unnecessary investigations. We hereby review and illustrate atypical presentations of the disease, including diverse forms of location and morphology of the lesions, the course of the eruption, and its differential diagnoses.

Pityriasis Rosea: An Update on Etiopathogenesis and Management of Difficult Aspects

Pityriasis rosea (PR) is a benign papulosquamous disorder seen commonly in clinical practice. Despite its prevalence and benign nature, there are still times when this common disorder presents in an uncommon way or course posing diagnostic or management problems for the treating physician. The etiopathogenesis of PR has always been a dilemma, and extensive research is going on to elicit the exact cause. This review focuses mainly on the difficult aspects of this benign common disorder such as etiopathogenesis, atypical manifestations, recurrent cases, differential diagnosis, therapy and pregnancy considerations. Although we could not find a black and white solution to all these problems, we have tried to compile the related literature to draw out some conclusions.

Pityriasis Rosea: A Comprehensive Classification

Pityriasis rosea (PR) is an acute, self-limiting exanthematous disease associated with the endogenous systemic reactivation of human herpesvirus (HHV)-6 and/or HHV-7. The disease typically begins with a single, erythematous plaque followed by a secondary eruption with lesions on the cleavage lines of the trunk (configuration of a 'Christmas tree'). The duration may vary from 2 weeks to a few months. Besides the typical presentation of PR, atypical forms have been described. The previous classifications of PR are mainly based on its atypical morphological features rather than on the pathogenetic mechanisms that underlie the different presentations of the disease. Notably, most of the morphologically atypical forms follow a course amenable to the classic form. The classification that we propose, taking into account the pathogenesis, clinical features, and course of the disease, is easy and intuitive and may be helpful in identifying the atypical forms of PR in order to avoid misdiagnosis and establish the best treatment options. Finally, this classification provides indications for managing potentially harmful forms of PR (such as PR in pregnancy) and PR-like eruptions.

Pitiríase rósea

Pitiríase rósea é doença inflamatória aguda da pele, que regride espontaneamente, normalmente sem deixar seqüelas, em período que varia de quatro a oito semanas. Clinicamente é caracterizada pelo aparecimento de típicas lesões eritêmato-pápulo-escamosas. Atinge todas as idades, embora seja mais comumente observada entre 10 e 35 anos. Apesar de exaustivas pesquisas, sua etiologia ainda permanece desconhecida. São discutidos alguns aspectos epidemiológicos, anatomoclínicos, diagnósticos diferenciais, doenças associadas, com ênfase no tratamento e etiologia da doença.

Atypical presentations of pityriasis rosea: case presentations

Atypical cases of pityriasis rosea (PR) are fairly common and less readily recognized than typical eruptions. We present four patients for whom we believe atypical PR is the most likely diagnosis. A 33-year-old man had purpuric lesions bilaterally on the legs with classical rash on the trunk. A 28-year-old woman had intensely pruritic and urticarial lesions. A 10-year-old girl had hundreds of small papular lesions 1-3 mm in size. A pregnant woman aged 26 had oral haemorrhagic ulcers with classical PR eruption on her trunk. The oral ulcers erupted and remitted at the same time as the generalized eruption. We reviewed the literature and proposed a classification based on rash morphology, rash size, rash distribution, number of lesions, site of lesions, severity of symptoms and course of the eruption. We believe that it is difficult to make a clear division to define typical and atypical PR, and that it is important not to ascribe any unusual or atypical skin eruption with PR unless other dermatoses have been excluded.