Symptoms usually last for 2–8 days. Influenza can cause people to miss work or school, and it is associated with decreased job performance and, in older adults, reduced independence. Fatigue and malaise may last for several weeks after recovery, and healthy adults may experience pulmonary abnormalities that can take several weeks to resolve. Complications and mortality primarily occur in high-risk populations and those who are hospitalized. Severe disease and mortality are usually attributable to pneumonia from the primary viral infection or a secondary bacterial infection, which can progress to ARDS.Other respiratory complications that may occur include sinusitis, bronchitis, bronchiolitis, excess fluid buildup in the lungs, and exacerbation of chronic bronchitis and asthma. Middle ear infection and croup may occur, most commonly in children. Secondary S. aureus infection has been observed, primarily in children, to cause toxic shock syndrome after influenza, with hypotension, fever, and reddening and peeling of the skin. Complications affecting the cardiovascular system are rare and include pericarditis, fulminant myocarditis with a fast, slow, or irregular heartbeat, and exacerbation of pre-existing cardiovascular disease. Inflammation or swelling of muscles accompanied by muscle tissue breaking down occurs rarely, usually in children, which presents as extreme tenderness and muscle pain in the legs and a reluctance to walk for 2–3 days.Influenza can affect pregnancy, including causing smaller neonatal size, increased risk of premature birth, and an increased risk of child death shortly before or after birth. Neurological complications have been associated with influenza on rare occasions, including aseptic meningitis, encephalitis, disseminated encephalomyelitis, transverse myelitis, and Guillain–Barré syndrome.
Erythema induratum is a panniculitis on the calves. It occurs mainly in women, but it is very rare now. Historically, when it has occurred, it has often been concomitant with cutaneous tuberculosis, and it was formerly thought to be always a reaction to the TB bacteria. It is now considered a panniculitis that is not associated with just a single defined pathogen. The medical eponym Bazin disease was historically synonymous, but it applies only to the tuberculous form and is dated. Pathophysiology
Predisposing factors include abnormal amount of subcutaneous fat, thick ankles and abnormally poor arterial supply. Abnormal arterial supply causes low-grade ischemia of ankle region. The ankle skin becomes sensitive to temperature changes. When weather is cold, ankle is cold, blue and often tender. In hot weather, ankle becomes hot, edematous, swollen and painful. Chilblains may be present. On palpation, small superficial and painful nodules are felt. They break down to form small and multiple ulcers. Fresh crops of nodules appear in periphery of ulcer and ultimately break down. In nodular stage, pain is present; while it subsides in ulcerative stage. Diagnosis
Mainly clinical. Eponym
The name Bazin disease honors Pierre-Antoine-Ernest Bazin. Additional images
References
External links
 Media related to Erythema induratum at Wikimedia Commons
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