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Autumn 2017, Vol. 25 No. 3

Hong Kong J. Dermatol. Venereol. (2017) 25, 155

Answers to Dermato-venereological Quiz

CMT Cheung 張敏彤, MM Chang 張苗, PCL Choi 蔡祥龍

Clinical differential diagnoses include pretibial mxyoedema, lipodermatosclerosis, hypertrophic lichen planus, lichen simplex chronicus, cutaneous lymphoma, lymphoedema, atypical mycobacterial infection, and deep fungal infection.
Histopathological examination of the skin biopsy showed expanded spaces between collagen in dermis. Alcian blue stain demonstrated abundant stromal mucin deposition.
The diagnosis is pretibial myxoedema. It is characterised by pretibial indurated plaques due to dermal deposition of mucin. Though the exact pathogenesis is unknown, it is thought to be caused by auto-antibodies inciting fibroblasts to produce mucin. Pretibial myxoedema primarily affects young to middle-aged women with thyroid disease, most commonly Graves' disease. They usually present with erythematous to skin-coloured, sometimes yellowish indurated nodules or plaques on shins, often associated with hypertrichosis and prominent hair follicles, giving rise to a peau d'orange appearance.
Treatment can be challenging. First-line treatment includes potent topical steroids under occlusion, intralesional steroids, and compressive therapy. Oral pentoxifylline has been shown to be effective in small case series. Other treatment such as IVIG, plasmapheresis, cytotoxic agents, and surgical excision may provide temporary improvement and are usually reserved for severe refractory cases. Treatments of underlying thyroid disease does not improve cutaneous lesions. Spontaneous resolution occasionally occurs after years.