Pneumocystosis is a fungal infection that most often presents as Pneumocystis pneumonia in people with HIV/AIDS or poor immunity. It usually causes cough, difficulty breathing and fever, and can lead to respiratory failure. Involvement outside the lungs is rare but, can occur as a disseminated type affecting lymph nodes, spleen, liver, bone marrow, eyes, kidneys, thyroid, gastrointestinal tract or other organs. If occurring in the skin, it usually presents as nodular growths in the ear canals or underarms. It is caused by Pneumocystis jirovecii, a fungus which is usually breathed in and found in the lungs of healthy people without causing disease, until the person's immune system becomes weakened. Diagnosis is by identifying the organism from a sample of fluid from affected lungs or a biopsy. Prevention in high risk people, and treatment in those affected is usually with trimethoprim/sulfamethoxazole (co-trimoxazole). The prevalence is unknown. Less than 3% of cases do not involve the lungs. The first cases of pneumocystosis affecting lungs were described in premature infants in Europe following the Second World War. Signs and symptoms Pneumocystosis is generally an infection in the lungs. Involvement outside the lungs is rare but, can occur as a disseminated type affecting lymph nodes, bone marrow, liver or spleen. It may also affect skin, eyes, kidneys, thyroid, heart, adrenals and gastrointestinal tract. Lungs When the lungs are affected there is usually a dry cough, difficulty breathing and fever, usually present for longer than four weeks. There may be chest pain, shivering or tiredness. The oxygen saturation is low. The lungs may fail to function. Eyes Pneumocystosis in eyes may appear as a single or multiple (up to 50) yellow-white plaques in the eye's choroid layer or just beneath the retina. Vision is usually not affected and it is typically found by chance. Skin If occurring in the skin, pneumocystosis most often presents as nodular growths in the ear canals of a person with HIV/AIDS. There may be fluid in the ear. Skin involvement may appear outside the ear, usually palms, soles or underarms; as a rash, or small bumps with a dip. It can occur on the face as brownish bumps and plaques. The bumps may be tender and the ulcerate. Infection in the ear may result in a perforated ear drum or destruction of the mastoid bone. The nerves in the head may be affected. Cause Pneumocystosis is caused by Pneumocystis jirovecii,