Signs and symptoms of a<unk>  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.<unk>  can also appear later in life. This is referred to as "late-onset"<unk> . 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<unk>  can be asymptomatic. Symptom severity is predictably correlated with the severity of the enzyme defect. Profound<unk>  refers to situations where enzyme activity is 10% or less. Individuals with partial<unk>  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. In both cases, supplementation with biotin can often restore normal metabolic function and proper catabolism of leucine and isoleucine. The symptoms of<unk>  (and dietary deficiency of biotin) can be quite severe. A 2004 case study from Metametrix detailed the effects of biotin deficiency, including aggression, cognitive delay, and reduced immune function.
Biotinidase deficiency
D-bifunctional protein deficiency
Glutaminase deficiency
Aromatic L-amino acid decarboxylase deficiency
Ornithine aminotransferase deficiency
Enolase deficiency
Arginine:glycine amidinotransferase deficiency
Holocarboxylase synthetase deficiency