Poikiloderma with neutropenia
Poikiloderma with neutropenia (PN) is a disorder that mainly affects the skin and the immune system. This condition begins with a bumpy rash that usually appears 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, and the affected child is left with darker and lighter patches of skin coloring (hyperpigmentation and hypopigmentation) and small clusters of blood vessels just under the skin (telangiectases); this combination is known as poikiloderma. Other skin problems include unusually thick skin on the palms of the hands and soles of the feet (palmoplantar keratoderma); calcium deposits that form small nodules (calcinosis cutis), especially on the knees, elbows, or ears; or sores (ulcers) that do not easily heal. Affected individuals also have fingernails and toenails that are thick and abnormally shaped (pachyonychia), fragile teeth, and low bone density.
People with PN have chronic neutropenia, which is a persistent shortage (deficiency) of neutrophils. Neutrophils are a type of white blood cell that plays a role in inflammation and in fighting infection. Neutropenia makes it more difficult for the body to fight off pathogens such as bacteria and viruses. As a result, people with PN experience recurrent sinus infections and pneumonia, especially in the first few years of life. They often develop a condition called bronchiectasis, which damages the passages leading from the windpipe to the lungs (bronchi) and can cause breathing problems. The infections become less frequent after early childhood, but throughout life affected individuals usually have a chronic cough or a reactive airway disease. This term describes asthma and other conditions in which the airways abnormally constrict in response to stimuli such as smoke or a viral infection, leading to wheezing and shortness of breath.
Researchers suggest that PN may increase the risk of cancer, although the level of risk is difficult to determine because only a small number of people have been diagnosed with PN. A type of skin cancer called squamous cell carcinoma, a precancerous blood disorder known as myelodysplastic syndrome (MDS), and a blood cancer called acute myelogenous leukemia that often follows MDS have occurred in a few people with PN.
Some individuals with PN also develop unusual facial features as they grow. These features include a prominent forehead (frontal bossing), widely spaced eyes (hypertelorism), a flat or sunken appearance of the middle of the face (midface hypoplasia), a small nose with a depressed nasalbridge, and a chin that protrudes (prognathism). Short stature and hypogonadotropic hypogonadism (a condition affecting the production of hormones that direct sexual development) can also occur in this disorder.
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