Tretinoin, also known as all-trans retinoic acid (ATRA), is a medication used for the treatment of acne and acute promyelocytic leukemia. For acne, it is applied to the skin as a cream, gel or ointment. For leukemia, it is taken by mouth for up to three months. Topical tretinoin is also the most extensively investigated retinoid therapy for photoaging.Common side effects when used as a cream are limited to the skin and include skin redness, peeling, and sun sensitivity. When used by mouth, side effects include shortness of breath, headache, numbness, depression, skin dryness, itchiness, hair loss, vomiting, muscle pains, and vision changes. Other severe side effects include high white blood cell counts and blood clots. Use during pregnancy is contraindicated due to the risk of birth defects. It is in the retinoid family of medications.Tretinoin was patented in 1957, and approved for medical use in 1962. It is on the World Health Organizations List of Essential Medicines. Tretinoin is available as a generic medication. In 2019, it was the 244th most commonly prescribed medication in the United States, with more than 1 million prescriptions. Medical uses
Skin use
Tretinoin is most commonly used to treat acne, both inflammatory and noninflammatory. Multiple studies support the efficacy of topical retinoids in the treatment of acne vulgaris. It is sometimes used in conjunction with other topical acne medications to enhance their penetration. In addition to treating active acne, retinoids accelerate the resolution of acne-induced postinflammatory hyperpigmentation.
Idiopathic interstitial pneumonia (IIP), or noninfectious pneumonia are a class of diffuse lung diseases. These diseases typically affect the pulmonary interstitium, although some also have a component affecting the airways (for instance, cryptogenic organizing pneumonitis). There are seven recognized distinct subtypes of IIP. Diagnosis
Classification can be complex, and the combined efforts of clinicians, radiologists, and pathologists can help in the generation of a more specific diagnosis.Idiopathic interstitial pneumonia can be subclassified based on histologic appearance into the following patterns:
Usual interstitial pneumonia is the most common type. Development
Table 1: Development of the (histologic) idiopathic interstitial pneumonia classification

UIP=usual interstitial pneumonia; DAD=diffuse alveolar damage; NSIP=non-specific interstitial pneumonia; DIP=desquamative interstitial pneumonia; RB=respiratory bronchiolitis; BIP=bronchiolitis obliterans interstitial pneumonia; OP=organizing pneumonia; LIP=lymphoid interstitial pneumonia; LPD=lymphoproliferative disease (not considered a diffuse lung disease); GIP=giant cell interstitial pneumonia; HMF=heavy metal fibrosis, no longer grouped with diffuse lung disease
Lymphoid interstitial pneumonia was originally included in this category, then excluded, then included again. References


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