SAMHD1 and sarcoidosis: There is a familial form of the disease, which manifests in childhood, of autosomal dominant inheritance, related to mutations in the TREX1 gene and less frequently in the SAMHD1 or TMEM173 genes.2, 36 The main differential diagnosis is idiopathic perniosis, but lupus pernio, an acral form of sarcoidosis, should also be considered as well as vasculitides and acral vasculopathies.