Pure Cutaneous Rosai Dorfman Disease: An Uncommon Location for a Rare Histiocytic Proliferative Disorder.

RosaiDorfman disease (RDD) is a rare, self-limiting disease of uncertain etiology involving lymph nodes as well as extranodal sites. Isolated or pure cutaneous RDD (PCRDD) without lymph node involvement is very unusual accounting for only 3% of all described cases of RDD. The clinical features of PCRDD are quite different from RDD according to the literature on extranodal RDD, thereby emphasizing that PCRDD is a distinct clinical entity. Histopathology remains the gold standard for the diagnosis of both systemic and PCRDD with the presence of characteristic emperipolesis observed in histiocytes while immunohistochemistry (IHC) (S100, CD 68 positive, and CD 1a-negative) serves as a useful adjunct. We hereby report a case of a 36-year-old female who presented with a tender, indurated plaque on the left forearm with a clinical differential diagnosis of borderline tuberculoid leprosy/sarcoidosis and lupus vulgaris. However, on histopathology, a diagnosis of RDD was performed and confirmed on IHC. This case highlights the need to create awareness among young pathologists and clinicians about PCRDD to prevent overzealous treatment.

Isolated distal cutaneous thrombosis: an unusual presentation and an interesting etiology.

A middle-aged hypertensive male, with a fatty liver and chronic alcohol intake, relocated to a high altitude of 2100 m above sea level; in the first winter season, he developed bluish skin lesions over the tip of the nose, margins of both ear lobes, both knees, and subungual location. Systemic examination was unremarkable. Skin biopsy showed thrombi in dermal vessels without any evidence of vasculitis; immunofluorescence was negative. Investigations revealed mild elevation in plasma homocysteine levels, weakly positive antinuclear antibodies and elevated antiphospholipid antibodies, methylene tetrahydrofolate reductase C677T heterozygosity, and protein S deficiency. The patient received prednisolone for 2 weeks, aspirin and pentoxyphylline for 3 months, and continues to be on folic acid and vitamin B6. After 3 months, antiphospholipid antibodies and antinuclear antibody levels were normal. Isolated distal cutaneous thrombosis is an uncommon entity and precipitation by extreme cold in a hypertensive male with three thrombophilic states - one transient, one hereditary, and one acquired - is fascinating.