Insect bites and stings occur when an insect is agitated and seeks to defend itself through its natural defense mechanisms, or when an insect seeks to feed off the bitten person. Some insects inject formic acid, which can cause an immediate skin reaction often resulting in redness and swelling in the injured area. Stings from fire ants, bees, wasps and hornets are usually painful, and may stimulate a dangerous allergic reaction called anaphylaxis for at-risk patients, and some wasps can also have a powerful bite along with a sting. Bites from mosquitoes and fleas are more likely to cause itching than pain. The skin reaction to insect bites and stings usually lasts for up to a few days. However, in some cases, the local reaction can last for up to two years. These bites are sometimes misdiagnosed as other types of benign or cancerous lesions. Signs and symptoms
The reaction to a sting is of three types. The normal reaction involves the area around the bite with redness, itchiness, and pain. A large local reaction occurs when the area of swelling is greater than 5 centimetres (2 in). Systemic reactions are when symptoms occur in areas besides that of the bites.With insect stings a large local reaction may occur (an area of skin redness greater than 10 centimetres (4 in) in size). It can last one to two days. It occurs in about 10% of those bitten.
Persistent hyperplastic primary vitreous (PHPV), also known as persistent fetal vasculature (PFV), is a rare congenital developmental anomaly of the eye that results following failure of the embryological, primary vitreous and hyaloid vasculature to regress. It can be present in three forms: purely anterior (persistent tunica vasculosa lentis and persistent posterior fetal fibrovascular sheath of the lens), purely posterior (falciform retinal septum and ablatio falcicormis congenita) and a combination of both. Most examples of PHPV are unilateral and non-hereditary. When bilateral, PHPV may follow an autosomal recessive or autosomal dominant inheritance pattern. Symptoms
The primary vitreous used in formation of the eye during fetal development remains in the eye upon birth and is hazy and scarred. The symptoms are leukocoria, strabismus, nystagmus and blurred vision, blindness. Causes
Trisomy 13 (Patau syndrome)
Norrie disease
Walker-Warburg syndrome
Autosomal dominant
Autosomal recessive

Diagnosis
Causes a white reflex in the affected eye (leukocoria), prompting further investigation. Treatment
Pars plana lensectomy with or without vitrectomy and trabeculectomy. See also
Persistent tunica vasculosa lentis

References
External links

GeneReviews/NIH/NCBI/UW entry on NDP-Related Retinopathies