Before vaccination, croup was frequently caused by diphtheria and was often fatal. This cause is now very rare in the Western world due to the success of the diphtheria vaccine. Signs and symptoms
Croup is characterized by a "barking" cough, stridor, hoarseness, and difficult breathing which usually worsens at night. The "barking" cough is often described as resembling the call of a sea lion. The stridor is worsened by agitation or crying, and if it can be heard at rest, it may indicate critical narrowing of the airways. As croup worsens, stridor may decrease considerably.Other symptoms include fever, coryza (symptoms typical of the common cold), and indrawing of the chest wall–known as Hoovers sign. Drooling or a very sick appearance can indicate other medical conditions, such as epiglottitis or tracheitis. Causes
Croup is usually deemed to be due to a viral infection. Others use the term more broadly, to include acute laryngotracheitis (laryngitis and tracheitis together), spasmodic croup, laryngeal diphtheria, bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis. The first two conditions involve a viral infection and are generally milder with respect to symptomatology; the last four are due to bacterial infection and are usually of greater severity. Viral
Viral croup or acute laryngotracheitis is most commonly caused by parainfluenza virus (a member of the paramyxovirus family), primarily types 1 and 2, in 75% of cases. Other viral causes include influenza A and B, measles, adenovirus and respiratory syncytial virus (RSV).
Muehrckes nails or Muehrckes lines (apparent leukonychia striata) are changes in the fingernail that may be a sign of an underlying medical condition. The term refers to a set of one or more pale transverse bands extending all the way across the nail, parallel to the lunula. In contrast to Beaus lines, they are not grooved (no 3-dimensional deformity), and in contrast to Mees lines, the thumb is usually not involved.Muehrckes lines are a strong indicator of hypoalbuminemia, which can result from a variety of different causes.The lines are actually in the vascular bed underneath the nail plate. As such, they do not move with nail growth, and disappear when pressure is applied to the nail (blanching the underlying nail bed): this distinguishes them from "true leukonychia striata" such as Mees lines. As in Terrys and half-and-half nails, the pattern is thought to be formed by bands of localized edema exerting pressure on the surrounding capillaries. Physiology
The appearance of Muehrckes lines is associated specifically with marked hypoalbuminemia (serum albumin ≤ 2.2 g/dL) indicating decreased protein synthesis, which may occur during periods of metabolic stress (e.g. systemic infection, trauma, AIDS, chemotherapy), or in hypoalbuminemic states such as the nephrotic syndrome or dietary protein deficiency.