Biotinidase deficiency is an autosomal recessive metabolic disorder in which biotin is not released from proteins in the diet during digestion or from normal protein turnover in the cell. This situation results in biotin deficiency. Biotin is an important water-soluble nutrient that aids in the metabolism of fats, carbohydrates, and proteins. Biotin deficiency can result in behavioral disorders, lack of coordination, learning disabilities and seizures. Biotin supplementation can alleviate and sometimes totally stop such symptoms. Signs and symptoms
Signs and symptoms of a biotinidase deficiency can appear several days after birth. These include seizures, hypotonia and muscle/limb weakness, ataxia, paresis, hearing loss, optic atrophy, skin rashes (including seborrheic dermatitis and psoriasis), and alopecia. If left untreated, the disorder can rapidly lead to coma and death.Biotinidase deficiency can also appear later in life. This is referred to as "late-onset" biotinidase deficiency. The symptoms are similar, but perhaps more mild, because if an individual survives the neonatal period they likely have some residual activity of biotin-related enzymes. Studies have noted individuals who were asymptomatic until adolescence or early adulthood. One study pointed out that untreated individuals may not show symptoms until age 21. Furthermore, in rare cases, even individuals with profound deficiencies of biotinidase can be asymptomatic.Symptom severity is predictably correlated with the severity of the enzyme defect. Profound biotinidase deficiency refers to situations where enzyme activity is 10% or less. Individuals with partial biotinidase deficiency may have enzyme activity of 10-30%.Functionally, there is no significant difference between dietary biotin deficiency and genetic loss of biotin-related enzyme activity.
insufficient blood flow to portions of the heart), and be accompanied by potentially serious abnormalities in the rhythm of heart beats, i.e. arrythmias. The only evidence of the presence of totally asymptomatic variant angina would be detection of diagnostic changes on fortuitously conducted ECGs. Risk factors
The intake of certain agents have been reported to trigger an attack of variant angina. These agents include:

recreational agents (e.g. nicotine in tobacco and other forms, alcoholic beverages, marijuana, cocaine);
catecholamine-like stimulants (e.g. epinephrine, dopamine, various amphetamines);
the uterus-contracting drug, ergonovine;
parasympathomimetic drugs (e.g. acetylcholine, methacholine);
anti-migraine drugs (e.g. various triptans);
chemotherapeutic drugs (e.g. 5-fluorouracil, capecitabine);
high consumption of energy drinks have been associated with variant angina.In addition, hyperventilation and virtually any stressful emotional or physical (e.g. cold exposure) event that is suspected of causing significant rises in the blood levels of catecholamines may trigger variant angina. Mechanism
The mechanism that causes such intense vasospasm, as to cause a clinically significant narrowing of the coronary arteries is so far unknown, but there are three relevant hypotheses:

Enhanced contractility of coronary vascular smooth muscle due to reduced nitric oxide bioavailability caused by a defect in the endothelial nitric oxide synthetase enzyme which leads to endothelial function abnormalities.Acetylcholine is normally released by the parasympathetic nervous system (PSNS) at rest, and causes dilation of the coronary arteries. While acetylcholine induces vasoconstriction of vascular smooth muscle cells through a direct mechanism, acetylcholine also stimulates endothelial cells to produce nitric oxide (NO). NO then diffuses out of the endothelial cells, stimulating relaxation of the nearby smooth muscle cells.