This means a defective gene responsible for the disorder is located on an autosome, and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder. Pathophysiology
At present, no specific enzyme deficiency nor genetic mutation has been implicated as the cause of hypertryptophanemia. Several known factors regarding tryptophan metabolism and kynurenines, however, may explain the presence of behavioral abnormalities seen with the disorder.Tryptophan is an essential amino acid, and is required for protein synthesis. Aside from this crucial role, the remainder of tryptophan is primarily metabolized along the kynurenine pathway in most tissues, including those of the brain and central nervous system.As the main defect behind hypertryptophanemia is suspected to alter and disrupt the metabolic pathway from tryptophan to kynurenine, a possible correlation between hypertryptophanemia and the known effects of kynurenines on neuronal function, physiology and behavior may be of interest.One of these kynurenines, aptly named kynurenic acid, serves as a neuroprotectant through its function as an antagonist at both nicotinic and glutamate receptors (responsive to the neurotransmitters nicotine and glutamate, respectively). This action is in opposition to the agonist quinolinic acid, another kynurenine, noted for its potential as a neurotoxin.
Studies suggest that CVG often occurs in individuals in a secondary form to other ailments. However, the condition can also be present on its own. CVG can be classified into two forms: ‘primary’ (essential and non-essential) and ‘secondary’.The classifications are:

Primary essential
Primary non-essential
SecondaryPrimary essential CVG is where the cause of the condition in unknown. It has no other associated abnormalities. This occurs mainly in men, with a male:female ratio of 5:1 or 6:1, and develops during or soon after puberty. Because of the slow progression of the condition, which usually occurs without symptom, it often passes unnoticed in the early stage.Primary non-essential CVG can be associated with neuropsychiatric disorders including cerebral palsy, epilepsy, seizures, and ophthalmologic abnormalities, most commonly cataracts.Secondary CVG occurs as a consequence of a number of diseases or drugs that produce changes in scalp structure. These include: acromegaly (excessive growth hormone levels due to pituitary gland tumours), and theoretically, the use of growth hormone itself or the use of drugs that mimic the effect of growth hormone (such as GHRP-6 and CJC-1295). It may also arise in association with melanocytic naevi (moles), birthmarks (including connective tissue naevi, fibromas and naevus lipomatosus), and inflammatory processes (e.g. eczema, psoriasis, Darier disease, folliculitis, impetigo, atopic dermatitis, acne). Treatment
Options for medical treatment for this condition have been limited to plastic surgery with excision of the folds by means of scalp reduction/surgical resection. Scalp subcision has also been suggested as a treatment. Additional suggestions also include injections of a dermal filler (e.g.