This results in conditions such as conjoined twins, and the resulting merged organism may die at birth when it must leave the life-sustaining environment of the womb and must attempt to sustain its biological processes independently. Genetics
Genetic causes of birth defects include inheritance of abnormal genes from the mother or the father, as well as new mutations in one of the germ cells that gave rise to the fetus. Male germ cells mutate at a much faster rate than female germ cells, and as the father ages, the DNA of the germ cells mutates quickly. If an egg is fertilized with sperm that has damaged DNA, a possibility exists that the fetus could develop abnormally.Genetic disorders are all congenital (present at birth), though they may not be expressed or recognized until later in life. Genetic disorders may be grouped into single-gene defects, multiple-gene disorders, or chromosomal defects. Single-gene defects may arise from abnormalities of both copies of an autosomal gene (a recessive disorder) or of only one of the two copies (a dominant disorder). Some conditions result from deletions or abnormalities of a few genes located contiguously on a chromosome. Chromosomal disorders involve the loss or duplication of larger portions of a chromosome (or an entire chromosome) containing hundreds of genes. Large chromosomal abnormalities always produce effects on many different body parts and organ systems. Socioeconomics
A low socioeconomic status in a deprived neighborhood may include exposure to "environmental stressors and risk factors".
Vernal keratoconjunctivitis (VKC) is a recurrent, bilateral, and self-limiting inflammation of conjunctiva, having a periodic seasonal incidence. Vernal keratopathy
Corneal involvement in VKC may be primary or secondary due to extension of limbal lesions. Vernal keratopathy includes 5 types of lesions. Punctuate epithelial keratitis. Ulcerative vernal keratitis (shield ulceration). Vernal corneal plaques. Subepithelial scarring. Pseudogerontoxon. Sign and symptoms
Symptoms- VKC is characterised by marked burning and itchy sensations which may be intolerable and accentuates when patient comes in a warm humid atmosphere. Associated symptoms include mild photophobia in case of corneal involvement, lacrimation, stringy discharge and heaviness of eyelids. Signs of VKC can be described in three clinical forms (Cameron Classification):Palpebral form- Usually upper tarsal conjunctiva of both the eyes is involved. Typical lesion is characterized by the presence of hard, flat-topped papillae arranged in cobblestone or pavement stone fashion. In severe cases papillae undergo hypertrophy to produce cauliflower-like excrescences of giant papillae. Bulbar form- It is characterised by dusky red triangular congestion of bulbar conjunctiva in palpebral area, gelatinous thickened accumulation of tissue around limbus and presence of discrete whitish raised dots along the limbus (Trantas spots). Mixed form- Shows the features of both palpebral and bulbar types. Cause
VKC is thought to be an allergic disorder in which IgE mediated mechanism play a role. Such patients often give family history of other atopic diseases such as hay fever, asthma or eczema, and their peripheral blood shows eosinophilia and increased serum IgE levels. Risk factors
Age and sex – 4–20 years; more common in boys than girls.