A disorder of the skin and immune system with initial manifestation of a bumpy skin rash usually between the ages of 6 and 12 months, gradually spreading from the arms and legs to the torso and face. At about age 2, the rash fades leaving hyperpigmentation and hypopigmentation and telangiectases, this combination is known as poikiloderma. Palmoplantar keratoderma, calcinosis cutis, skin ulcers, pachyonychia, fragile teeth and low bone density may also be present. Chronic neutropenia is present resulting in recurrent sinus infections and pneumonia, especially in the first few years of life. Caused by mutations in the USB1 gene.