Onychomycosis is caused most commonly by Trichophyton rubrum or T. mentagrophytes. About 10% of all persons worldwide and 40% of those ≥60 years old are believed to have the disease. Risk factors include older age, diabetes, poor peripheral circulation, smoking, HIV infection, psoriasis, and immunosuppression. Left untreated, onychomycosis can cause nail plate destruction, ingrown nails, and (particularly in patients with diabetes) secondary infections. Guidelines on treatment of onychomycosis have been published.

View the Table: Some Drugs for Inflammatory Bowel Disease

Bipolar disorder is characterized by episodes of mania, hypomania, and depression. Recurrences of manic or (more frequently) depressive symptoms are common. About 15-20% of patients with bipolar disorder die by suicide.

Atopic dermatitis (AD; also known as eczema) is frequently associated with other atopic disorders such as allergic rhinitis, asthma, and food allergy. It commonly presents in infancy and early childhood and has a relapsing course, often improving by adolescence, but sometimes persisting into (or first appearing in) adulthood or even old age.

Rheumatoid arthritis (RA) is prevalent in 0.5% of adults in the US; it is about 2.5 times more common in women than in men. Guidelines for treatment of RA from the American College of Rheumatology were recently updated. The goal of treatment is to minimize disease activity and prevent irreversible joint damage.

Ulcerative colitis (UC) and Crohn's disease (CD), referred to collectively as inflammatory bowel disease (IBD), are chronic immune-mediated inflammatory conditions. Guidelines for treatment of UC and CD have been updated in recent years

Patients who receive pretravel advice can reduce their risk for many travel-related conditions. Vaccines recommended for travelers are reviewed in a separate issue.

View the Table: Treatments Considered for COVID-19

With increasing travel, immigration, use of immunosuppressive drugs and the spread of AIDS, physicians anywhere may see infections caused by parasites. The table in this document lists first-choice and alternative drugs for most parasitic infections.