Diagnosis

Pityriasis rosea

Etiology

Cause [rtb]

1. Unknown

2. Infection (human herpes virus 6/7, influenza, diphtheria, smallpox, hepatitis B, pneumococcus, and COVID-19, bacteria, and spirochetes) is suspected due to:

   • Prodrome phase: Sore throat, gastrointestinal disturbance, fever, and arthralgia

   • Seasonal variation

   • Community clustering

   • Low rate of recurrence, which suggests immunity

3. Noninfective causes like atopy, autoimmunity, vaccination, drugs (gold compounds, captopril, barbiturates, D-penicillamine, clonidine, ACE inhibitors, NSAIDs, hydrochlorothiazide, atypical antipsychotics, imatinib, metronidazole, isotretinoin, and clozapine)

Pathophysiology [rtb]

1. Not entirely understood

2. Trigger --> T-cell–mediated immune response --> characteristic skin pattern: [2s6]

   • A herald ("mother") patch surrounded by scaly oval plaques on the trunk and proximal extremities forming a characteristic "Christmas tree" appearance

Complications [rtb]

• Superimposed bacterial infection

• Itching, discomfort, and impaired quality of life

• Hyperpigmentation

• Recurrence

Epidemiology

Prevalence per 100.000 [g6n][zbd][rtb][4so][bsq][woz][pws][tzm][8sn][ktu]

Incidence per 100.000 [g6n][zbd][rtb][4so][bsq][woz][pws][tzm][8sn][ktu]

Approach

• Dermatoscopy

• Biopsy

• Exclude syphilis

Diagnostic criteria [eir][yp7]

1. Essential clinical features:

   • Discrete circular or oval lesions

   • Scaling on most lesions, and

   • Peripheral collarette scaling with central clearance on at least two lesions

2. Optional clinical features:

   • Truncal and proximal limb distribution

   • Orientation of most lesions along skin cleavage lines

   • A herald patch (not necessarily the largest) appearing at least two days before eruption of other lesions

3. Exclusional clinical features:

   • Multiple small vesicles at the centre of two or more lesions

   • Two or more lesions on palmar or plantar skin surfaces

   • Clinical or serological evidence of secondary syphilis

Treatment

1. Self-limiting disease

2. Supportive therapy: [rtb][eir]

   • Moisturizers

   • Bathing with soap alternatives

   • Cautious sunlight exposure without burning

   • Emollients

   • Antihistamines

3. Therapy

   • Topical steroids

   • Acyclovir (considered in severe cases)

   • Macrolides (no proven benefit)

   • Narrowband ultraviolet B therapy

Differential diagnoses

Drug eruptions, Eczema, Erythema multiforme, Kaposi sarcoma, Lichen planus, Parapsoriasis, Pityriasis alba, Pityriasis versicolor, Psoriasis, Seborrheic dermatitis, Syphilis, Tinea corporis, Tinea versicolor