Résumé : Primary immunodeficiency disorders comprise serious and rare diseases, predominantly in children. The skin may be involved in a primary immunodeficiency and the cutaneous alterations such as infections, eczematous dermatitis, erythroderma, autoimmune dermatoses and vasculitis may be the basis for the ultimate diagnosis. Dermatologists may realize something is wrong with the immunity of their patient and prompt diagnosis of the defect can lead to lifesaving treatment. Since atypical presentations of well known dermatoses are common in immunodeficiency disorders, histopathology and bacterial, fungal or viral tests of the skin lesions are often indispensable. The knowledge of skin findings in primary immunodeficiency diseases may help dermatologists to play a role in the early detection of these diseases. Key findings constitute specific skin symptoms combined with unusual or severe infections.