A genetic cause of Alzheimer disease: mechanistic insights from Down syndrome

Down syndrome, caused by an extra copy of chromosome 21, is associated with a greatly increased risk of early onset Alzheimer disease. It is thought that this risk is conferred by the presence of three copies of the gene encoding amyloid precursor protein (APP), an Alzheimer risk factor, although the possession of extra copies of other chromosome 21 genes may also play a role. Further study of the mechanisms underlying the development of Alzheimer disease in Down syndrome could provide insights into the mechanisms that cause dementia in the general population

Granuloma Annulare

Granuloma annulare (GA) is an inflammatory dermatosis of adults and children, arranged by groups of skin\u2010coloured to erythematous papules in an annular distribution. Nodular lesions may be present too. Common sites of GA are the extensor surfaces of the limbs, dorsa of hands and feet; scalp and trunk are rarely affected. The aetiology of GA is unclear, but some pathological associations have been reported, such as diabetes mellitus type 1, infections, haematological and autoimmune disorders. Four main clinical variants of GA are known: localized GA (multiple or single), subcutaneous GA, generalized GA (annular or nonannular) and perforating GA. Adjunctive rare variants are papular umbilicated GA and linear GA. Clinical features are crucial for suspecting GA, but in doubtful cases biopsy and histopathology are mandatory to confirm the diagnosis. Three main microscopic patterns have been described: palisading granulomatous, interstitial histiocytic and sarcoidal. GA is usually benign and self\u2010limiting so clinical follow\u2010up represents the first\u2010choice therapeutic option. Other topical or systemic measures have shown controversial results