Pityriasis roseahttps://en.wikipedia.org/wiki/Pityriasis_rosea
Pityriasis rosea is a type of skin rash. It begins with a single red, slightly scaly area, followed days to weeks later by a rash of many similar but smaller round or oval lesions, mainly on the trunk and upper limbs. The condition usually lasts less than three months and resolves without treatment. Occasionally, malaise, fever, or itchiness may occur before the rash appears, but other symptoms are often minimal.

Although the exact cause is unclear, it is thought to be related to human herpesvirus 6 or human herpesvirus 7. The rash is not contagious. Certain medications can produce a similar eruption. Diagnosis is clinical, and a biopsy is usually unnecessary.

As a common condition, about 1.3 % of people are affected at some point. It most commonly occurs in individuals aged 10 to 35.

○ Diagnosis and Treatment
If the rash persists for more than one month, a detailed work‑up may be needed to distinguish it from other diseases (parapsoriasis, syphilis).

#Phototherapy
#OTC steroid ointment
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  • Pityriasis rosea on the back ― Asymptomatic macules and patches, unlike drug eruptions which usually itch.
  • herald patch ― A large scaly patch that starts before the rest of the lesion and is initially mistaken for a fungal infection.
  • Pityriasis rosea on torso ― Most of the lesions are located on the torso because sunlight improves the lesion.
  • If it itches a lot, you may suspect an allergic disease such as nummular eczema.
  • pityriasis rosea or guttate psoriasis
  • Small herald patch.
References Pityriasis Rosea 28846360 
NIH
Pityriasis rosea, also known as pityriasis circinata, roseola annulata, and herpes tonsurans maculosus is an acute self-limiting papulosquamous disorder. It is often characterized by an initial herald patch, followed by scaly oval patches within 2 weeks. However, the herald patch is not always present. The scaly oval patches typically distribute in a Christmas-tree pattern on the trunk and proximal extremities. This activity reviews the evaluation and treatment of pityriasis rosea and the importance of the interprofessional team in recognizing and managing patients with this condition.
 Gianotti-Crosti syndrome, pityriasis rosea, asymmetrical periflexural exanthem, unilateral mediothoracic exanthem, eruptive pseudoangiomatosis, and papular-purpuric gloves and socks syndrome: a brief review and arguments for diagnostic criteria 24470919 
NIH
 Pityriasis Rosea: Diagnosis and Treatment. 29365241
Pityriasis rosea is a common rash that usually begins with a single patch on the trunk and spreads to cover the trunk and limbs. Diagnosis relies on clinical examination. The initial patch appears red with a raised border and sunken center. The rash typically emerges about two weeks later. Patients may experience fatigue, nausea, headaches, joint pain, swollen lymph nodes, fever, and sore throat alongside the rash. Similar conditions include syphilis, seborrheic dermatitis, eczema, and others. Treatment aims to alleviate symptoms with corticosteroids or antihistamines. Acyclovir may help in some cases. Severe instances may benefit from UV phototherapy. The disease during pregnancy sometimes has been linked to miscarriage.
 Pityriasis rosea in pregnancy: A case series and literature review 35616213 
NIH
In most cases, PR does not influence pregnancy or birth outcomes. Analysis of pooled data from our study and from previous studies revealed that the week of pregnancy at onset of PR was inversely associated with an unfavorable outcome (odds ratio [OR] = 0.937; 95 % CI 0.883 to 0.993). In addition, duration of PR (OR = 1.432; 95 % CI 1.129 to 1.827), additional extracutaneous symptoms (OR = 4.112; 95 % CI 1.580 to 10.23), and widespread rash distribution (OR 5.203, 95 % CI 1.702 to 14.89) were directly associated with unfavorable outcome.
 Clinical variants of pityriasis rosea 28685133 
NIH
Pityriasis rosea (PR) is a relatively common, self-limited papulo-squamous dermatosis of unknown origin, which mainly appears in adolescents and young adults (10-35 years), slightly more common in females. It has a sudden onset, and in its typical presentation, the eruption is preceeded by a solitary patch termed “herald patch”, mainly located on the trunk. Few days later, a secondary eruption appears, with little pink, oval macules, with a grayish peripheral scaling collarette around them. The secondary lesions adopt a characteristic distribution along the cleavage lines of the trunk, with a configuration of a “Christmas tree”. In most cases, the eruption lasts for 6 to 8 wk. Its incidence has been estimated to be 0.68% of dermatologic patients, varying from 0.39% to 4.8%.