Pityriasis rubra pilaris (PRP) is an idiopathic, papulosquamous inflammatory dermatosis. It is characterized by hyperkeratotic follicular papules coalescing into orange-red scaly plaques, islands of sparing, and palmoplantar keratoderma. PRP can be subdivided into six clinical subtypes according to Griffiths' classification, based on age of onset, disease extent, prognosis, and other associated features. The sixth subtype of PRP occurs in individuals affected by HIV infection, and retroviral screening in all de novo cases of PRP is advised. Other reported associations include various infections, autoimmunity, drugs, and malignancies, although the true significance of these is still unclear. The genetic basis for familial cases, most commonly categorized under the fifth subtype, has been mapped to gain of function mutations in the caspase recruitment domain family, member 14 (CARD14) gene. Treatment of PRP remains a challenge to this day due to a paucity of high-quality evidence. Therapeutic regimens have been guided mostly by case reports and case series, with the mainstay of treatment being oral retinoids. Recently, biologics have emerged as a promising treatment for PRP. We present a review of the clinicopathologic features, pathogenesis, associated disorders, and treatment of PRP, with an emphasis and critical appraisal of the existing literature on the latter.

Kimura's disease and angiolymphoid hyperplasia with eosinophilia can coexist in the same patient. Coexistence of the two types of lesions in one patient may also be considered evidence that Kimura's disease and angiolymphoid hyperplasia with eosinophilia form a spectrum in one disease.

Nail psoriasis is common, occurring in up to half of patients with psoriasis and in 90% of patients with psoriatic arthritis. Left untreated, it may progress to debilitating nail disease, which leads to significant functional impairment. The most common clinical signs of nail psoriasis are nail plate pitting and onycholysis. Other classical signs include oil drop discoloration, subungual hyperkeratosis, and splinter hemorrhages. The modified Nail Psoriasis Severity Index (mNAPSI) can be used to grade the severity of nail psoriasis, while the Nail Psoriasis Quality of Life Scale (NPQ10) is a questionnaire that evaluates the impact of nail psoriasis on the patient's functional status and quality of life. Treatment of nail psoriasis should be individualized according to the patient's preferences, severity of nail changes, and presence of skin and/or joint involvement. Both topical and intralesional therapies are safe and effective treatment modalities for nail disease, but are limited by poor adherence and pain, respectively. Systemic therapy such as oral retinoids may be considered for widespread nail disease causing significant morbidity. Among biologic agents, tumor necrosis factor-α inhibitors and T-cell-targeted therapies such as ustekinumab may be useful for refractory severe nail psoriasis.

Our data suggest that solar urticaria is an uncommon photodermatosis and a rare form of urticaria. Wheals were mostly elicited by visible light and/or UVA. A combination of antihistamines and sunscreens provided a useful form of therapy for patients with solar urticaria.

Sarcoidosis is a systemic noncaseating granulomatous disorder of unknown origin involving multiple organ systems. There has been no report so far to describe the epidemiological pattern of cutaneous involvement in sarcoidosis in South-East Asia with diverse ethnic groups. A retrospective study examining the clinicopathological features of all patients diagnosed with sarcoidosis at a tertiary dermatology centre in Singapore from 1980 to 2003 was conducted. Cutaneous sarcoidosis was diagnosed in 25 patients: 13 were Indian, 11 were Chinese and one was Eurasian. Cutaneous manifestations included papules, nodules, plaques and scarring alopecia. Extracutaneous involvement of lymph nodes (four patients), lungs (eight patients) and eyes (two patients) was seen. Eight patients had abnormal chest radiographic findings. Histopathological examination of skin lesions revealed noncaseating, epithelioid granulomatous infiltration in the dermis without evidence of mycobacterial infection, deep fungal infection or polarizable birefringent material. Treatment modalities included corticosteroids, hydroxychloroquine, isotretinoin, methotrexate and surgical excision. Five patients had complete resolution of the cutaneous lesions. Cutaneous sarcoidosis is rare in Asia and indeed in Singapore. Extracutaneous involvement is not uncommon and a thorough clinical evaluation should be undertaken.