Galli-Galli disease (GGD) is an autosomal-dominant genodermatosis characterized by reticulated hyperpigmentation and keratotic papules, primarily in the axillae and groin. It is a rare allelic variant of Dowling-Degos disease (DDD), both caused by mutations in the keratin 5 gene, KRT5. GGD can be distinguished from DDD by focal suprabasal acantholysis with minimal dyskeratosis. Other conditions discussed include Hailey-Hailey disease, confluent and reticulated papillomatosis, pemphigus vulgaris, and Darier disease, each with distinct clinical and histological features.

Reactive perforating collagenosis (RPC) is a primary perforating dermatosis characterized by the transepithelial elimination of collagen, often associated with type 2 diabetes mellitus and chronic renal disease. Up to 10% of hemodialysis patients develop RPC, presenting with red-brown, umbilicated, papulonodular lesions. Histopathology shows an invaginating epidermal process with prominent hyperplasia and a central plug of keratin. Various therapies, including retinoids, allopurinol, doxycycline, dupilumab, and phototherapy, have been reported as successful. The patient was treated with dupilumab and triamcinolone cream, with efficacy to be assessed at the next visit. Other conditions discussed include elastosis perforans serpiginosa, prurigo nodularis, and ecthyma, each with distinct histological features and associations.