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. In both cases, supplementation with biotin can often restore normal metabolic function and proper catabolism of leucine and isoleucine.

The symptoms of biotinidase deficiency (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 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, also called vitamin B, 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.

Loss of appetite and weight loss can occur. Additional signs are weakness, sore tongue, headaches, heart palpitations, irritability, and behavioral disorders. In adults, anemia (macrocytic, megaloblastic anemia) can be a sign of advanced folate deficiency.

Women with folate deficiency who become pregnant are more likely to give birth to low birth weight premature infants, and infants with neural tube defects. In infants and children, folate deficiency can lead to failure to thrive or slow growth rate, diarrhea, oral ulcers, megaloblastic anemia, neurological deterioration. Microcephaly, irritability, developmental delay, seizures, blindness and cerebellar ataxia can also be observed.

Vitamin E deficiency or hypovitaminosis E is a deficiency of vitamin E. It causes nerve problems due to poor conduction of electrical impulses along nerves due to changes in nerve membrane structure and function.

Copper deficiency can cause a wide variety of neurological problems including, myelopathy, peripheral neuropathy, and optic neuropathy.

Another common symptom of copper deficiency is peripheral neuropathy, which is numbness or tingling that can start in the extremities and can sometimes progress radially inward towards the torso. In an Advances in Clinical Neuroscience & Rehabilitation (ACNR) published case report, a 69-year-old patient had progressively worsened neurological symptoms. These symptoms included diminished upper limb reflexes with abnormal lower limb reflexes, sensation to light touch and pin prick was diminished above the waist, vibration sensation was lost in the sternum, and markedly reduced proprioception or sensation about the self’s orientation. Many people suffering from the neurological effects of copper deficiency complain about very similar or identical symptoms as the patient. This numbness and tingling poses danger for the elderly because it increases their risk of falling and injuring themselves. Peripheral neuropathy can become very disabling leaving some patients dependent on wheel chairs or walking canes for mobility if there is lack of correct diagnosis. Rarely can copper deficiency cause major disabling symptoms. The deficiency will have to be present for an extensive amount of time until such disabling conditions manifest.

Signs of vitamin E deficiency include the following:

- Neuromuscular problems-such as spinocerebellar ataxia and myopathies.

- Neurological problems-may include dysarthria, absence of deep tendon reflexes, loss of the ability to sense vibration and detect where body parts are in three dimensional space, and positive Babinski sign.

- Hemolytic anemia-due to oxidative damage to red blood cells

- Retinopathy

- Impairment of the immune response

There is also some laboratory evidence that vitamin E deficiency can cause male infertility.

Often symptoms will arise that indicate the body is not absorbing or making the lipoproteins that it needs. These symptoms usually appear "en masse", meaning that they happen all together, all the time. These symptoms come as follows:

- Failure to thrive/Failure to grow in infancy

- Steatorrhea/Fatty, pale stools

- Frothy stools

- Foul smelling stools

- Protruding abdomen

- Intellectual disability/developmental delay

- Developmental coordination disorder, evident by age ten

- Muscle weakness

- Slurred speech

- Scoliosis (curvature of the spine)

- Progressive decreased vision

- Balance and coordination problems

Selenium deficiency in combination with Coxsackievirus infection can lead to Keshan disease, which is potentially fatal. Selenium deficiency also contributes (along with iodine deficiency) to Kashin-Beck disease. The primary symptom of Keshan disease is myocardial necrosis, leading to weakening of the heart. Kashin-Beck disease results in atrophy, degeneration and necrosis of cartilage tissue. Keshan disease also makes the body more susceptible to illness caused by other nutritional, biochemical, or infectious diseases.

Selenium is also necessary for the conversion of the thyroid hormone thyroxine (T4) into its more active counterpart, triiodothyronine, and as such a deficiency can cause symptoms of hypothyroidism, including extreme fatigue, mental slowing, goiter, cretinism, and recurrent miscarriage.

Vitamin B deficiency can also cause symptoms of mania and psychosis, fatigue, memory impairment, irritability, depression, ataxia, and personality changes. In infants symptoms include irritability, failure to thrive, apathy, anorexia, and developmental regression.

Familial Isolated Vitamin E Deficiency is caused by mutations in the gene for a-tocopherol transfer protein.

Vitamin B deficiency can lead to anemia and neurologic dysfunction. A mild deficiency may not cause any discernible symptoms, but as the deficiency becomes more significant, symptoms of anemia may result, such as weakness, fatigue, light-headedness, rapid heartbeat, rapid breathing and pale color to the skin. It may also cause easy bruising or bleeding, including bleeding gums. GI side effects including sore tongue, stomach upset, weight loss, and diarrhea or constipation. If the deficiency is not corrected, nerve cell damage can result. If this happens, vitamin B deficiency may result in tingling or numbness to the fingers and toes, difficulty walking, mood changes, depression, memory loss, disorientation and, in severe cases, dementia.

The main syndrome of vitamin B deficiency is pernicious anemia. It is characterized by a triad of symptoms:

1. Anemia with bone marrow promegaloblastosis (megaloblastic anemia). This is due to the inhibition of DNA synthesis (specifically purines and thymidine)

2. Gastrointestinal symptoms: alteration in bowel motility, such as mild diarrhea or constipation, and loss of bladder or bowel control. These are thought to be due to defective DNA synthesis inhibiting replication in a site with a high turnover of cells. This may also be due to the autoimmune attack on the parietal cells of the stomach in pernicious anemia. There is an association with GAVE syndrome (commonly called watermelon stomach) and pernicious anemia.

3. Neurological symptoms: Sensory or motor deficiencies (absent reflexes, diminished vibration or soft touch sensation), subacute combined degeneration of spinal cord, seizures, or even symptoms of dementia and or other psychiatric symptoms may be present. Deficiency symptoms in children include developmental delay, regression, irritability, involuntary movements and hypotonia.

The presence of peripheral sensory-motor symptoms or subacute combined degeneration of spinal cord strongly suggests the presence of a B deficiency instead of folate deficiency. Methylmalonic acid, if not properly handled by B, remains in the myelin sheath, causing fragility. Dementia and depression have been associated with this deficiency as well, possibly from the under-production of methionine because of the inability to convert homocysteine into this product. Methionine is a necessary cofactor in the production of several neurotransmitters.

Each of those symptoms can occur either alone or along with others. The neurological complex, defined as "myelosis funicularis", consists of the following symptoms:

1. Impaired perception of deep touch, pressure and vibration, loss of sense of touch, very annoying and persistent paresthesias

2. Ataxia of dorsal chord type

3. Decrease or loss of deep muscle-tendon reflexes

4. Pathological reflexes — Babinski, Rossolimo and others, also severe paresis

Vitamin B deficiency can cause severe and irreversible damage, especially to the brain and nervous system. These symptoms of neuronal damage may not reverse after correction of hematological abnormalities, and the chance of complete reversal decreases with the length of time the neurological symptoms have been present.

Tinnitus may be associated with vitamin B deficiency.

Abetalipoproteinemia affects the absorption of dietary fats, cholesterol, and certain vitamins. People affected by this disorder are not able to make certain lipoproteins, which are molecules that consist of proteins combined with cholesterol and particular fats called triglycerides. This leads to a multiple vitamin deficiency, affecting the fat-soluble vitamin A, vitamin D, vitamin E, and vitamin K. However, many of the observed effects are due to vitamin E deficiency in particular.

The signs and symptoms of abetalipoproteinemia appear in the first few months of life (because pancreatic lipase is not active in this period). They can include failure to gain weight and grow at the expected rate (failure to thrive); diarrhea; abnormal spiny red blood cells (acanthocytosis); and fatty, foul-smelling stools (steatorrhea). The stool may contain large chunks of fat and/or blood. Other features of this disorder may develop later in childhood and often impair the function of the nervous system. They can include poor muscle coordination, difficulty with balance and movement (ataxia), and progressive degeneration of the retina (the light-sensitive layer in the posterior eye) that can progress to near-blindness (due to deficiency of vitamin A, retinol). Adults in their thirties or forties may have increasing difficulty with balance and walking. Many of the signs and symptoms of abetalipoproteinemia result from a severe vitamin deficiency, especially vitamin E deficiency, which typically results in eye problems with degeneration of the spinocerebellar and dorsal column tracts.

Folate deficiency is a low level of folic acid and derivatives in the body. Also known as vitamin B9, folate is involved in adenosine, guanine, and thymidine synthesis (part of DNA synthesis). Signs of folate deficiency are often subtle. Anemia is a late finding in folate deficiency and folate deficiency anemia is the term given for this medical condition. It is characterized by the appearance of large-sized, abnormal red blood cells (megaloblasts), which form when there are inadequate stores of folic acid within the body.

Selenium deficiency is relatively rare in healthy well-nourished individuals. Few cases in humans have been reported.

Familial Isolated Vitamin E Deficiency also known as Ataxia With Vitamin E Deficiency is a rare autosomal recessive neurodegenerative disease. Symptoms are similar to those of Friedreich ataxia.

Hartnup disease manifests during infancy with variable clinical presentation: failure to thrive, photosensitivity, intermittent ataxia, nystagmus, and tremor.

Nicotinamide is necessary for neutral amino acid transporter production in the proximal renal tubules found in the kidney, and intestinal mucosal cells found in the small intestine. Therefore, a symptom stemming from this disorder results in increased amounts of amino acids in the urine.

Pellagra, a similar condition, is also caused by low nicotinamide; this disorder results in dermatitis, diarrhea, and dementia.

Hartnup disease is a disorder of amino acid transport in the intestine and kidneys; otherwise, the intestine and kidneys function normally, and the effects of the disease occur mainly in the brain and skin. Symptoms may begin in infancy or early childhood, but sometimes they begin as late as early adulthood. Symptoms may be triggered by sunlight, fever, drugs, or emotional or physical stress. A period of poor nutrition nearly always precedes an attack. The attacks usually become progressively less frequent with age. Most symptoms occur sporadically and are caused by a deficiency of niacinamide. A rash develops on parts of the body exposed to the sun. Mental retardation, short stature, headaches, unsteady gait, and collapsing or fainting are common. Psychiatric problems (such as anxiety, rapid mood changes, delusions, and hallucinations) may also result.

This defect leads to a multi-systemic disorder of the connective tissue, muscles, central nervous system (CNS), and cardiovascular system. Homocystinuria represents a group of hereditary metabolic disorders characterized by an accumulation of the amino acid homocysteine in the serum and an increased excretion of homocysteine in the urine. Infants appear to be normal and early symptoms, if any are present, are vague.

Signs and symptoms of homocystinuria that may be seen include the following:

Babies with glutaric acidemia type 1 often are born with unusually large heads (macrocephaly). Macrocephaly is amongst the earliest signs of GA1. It is thus important to investigate all cases of macrocephaly of unknown origins for GCDH deficiency, given the importance of the early diagnosis of GA1.

Macrocephaly is a "pivotal clinical sign" of many neurological diseases. Physicians and parents should be aware of the benefits of investigating for an underlying neurological disorder, particularly a neurometabolic one, in children with head circumferences in the highest percentiles.

Affected individuals may have difficulty moving and may experience spasms, jerking, rigidity or decreased muscle tone and muscle weakness (which may be the result of secondary carnitine deficiency). Glutaric aciduria type 1, in many cases, can be defined as a cerebral palsy of genetic origins.

Classical homocystinuria, also known as cystathionine beta synthase deficiency or CBS deficiency, is an inherited disorder of the metabolism of the amino acid methionine, often involving cystathionine beta synthase. It is an inherited autosomal recessive trait, which means a child needs to inherit a copy of the defective gene from both parents to be affected.

A vitamin deficiency can cause a disease or syndrome known as an avitaminosis or hypovitaminosis. This usually refers to a long-term deficiency of a vitamin. When caused by inadequate nutrition it can be classed as a "primary deficiency", and when due to an underlying disorder such as malabsorption it can be classed as a "secondary deficiency". An underlying disorder may be metabolic as in a defect converting tryptophan to niacin. It can also be the result of lifestyle choices including smoking and alcohol consumption.

Examples are vitamin A deficiency, folate deficiency, scurvy, vitamin D deficiency, vitamin E deficiency, and vitamin K deficiency. In the medical literature, any of these may also be called by names on the pattern of "hypovitaminosis" or "avitaminosis" + "[letter of vitamin]", for example, hypovitaminosis A, hypovitaminosis C, hypovitaminosis D.

Conversely hypervitaminosis is the syndrome of symptoms caused by over-retention of fat-soluble vitamins in the body.

- Vitamin A deficiency can cause keratomalacia.

- Thiamine (vitamin B1) deficiency causes beriberi and Wernicke–Korsakoff syndrome.

- Riboflavin (vitamin B2) deficiency causes ariboflavinosis.

- Niacin (vitamin B3) deficiency causes pellagra.

- Pantothenic acid (vitamin B5) deficiency causes chronic paresthesia.

- Vitamin B6

- Biotin (vitamin B7) deficiency negatively affects fertility and hair/skin growth. Deficiency can be caused by poor diet or genetic factors (such as mutations in the BTD gene, see multiple carboxylase deficiency).

- Folate (vitamin B9) deficiency is associated with numerous health problems. Fortification of certain foods with folate has drastically reduced the incidence of neural tube defects in countries where such fortification takes place. Deficiency can result from poor diet or genetic factors (such as mutations in the MTHFR gene that lead to compromised folate metabolism).

- Vitamin B12 (cobalamin) deficiency can lead to pernicious anemia, megaloblastic anemia, subacute combined degeneration of spinal cord, and methylmalonic acidemia among other conditions.

- Vitamin C (ascorbic acid) short-term deficiency can lead to weakness, weight loss and general aches and pains. Longer-term depletion may affect the connective tissue. Persistent vitamin C deficiency leads to scurvy.

- Vitamin D (cholecalciferol) deficiency is a known cause of rickets, and has been linked to numerous health problems.

- Vitamin E deficiency causes nerve problems due to poor conduction of electrical impulses along nerves due to changes in nerve membrane structure and function.

- Vitamin K (phylloquinone or menaquinone) deficiency causes impaired coagulation and has also been implicated in osteoporosis

Patients with aceruloplasminemia develop a variety of movement problems. They may experience dystonia of the head and neck, resulting in repetitive movements and contortions. Other involuntary movements may also occur, such as tremors, chorea, blepharospasms, and grimacing. Affected individuals may also experience ataxia, the lack of coordination of muscle movements. Some develop psychiatric problems and midlife dementia. The type of neurological disruption corresponds to associated regions of iron deposition in the brain and liver.

In addition to neurological problems, affected individuals may have diabetes mellitus caused by iron damage to cells in the pancreas that make insulin. This impairs blood sugar regulation and leads to the signs and symptoms of diabetes.

Iron accumulation in the tissues and organs results in a corresponding iron deficiency in the blood, leading to anemia. Anemia and diabetes usually occur by the time an affected person is in his or her twenties.

Affected individuals also experience retinal degeneration caused by excess iron. The changes result in small opaque spots and areas of atrophy around the edges of the retina. These abnormalities usually do not affect vision but can be observed during an eye examination.

Vitamin B refers to a group of chemically similar compounds which can be interconverted in biological systems. Vitamin B is part of the vitamin B group of essential nutrients. Its active form, pyridoxal 5′-phosphate, serves as a coenzyme in some 100 enzyme reactions in amino acid, glucose, and lipid metabolism.

In the months following birth, signs and symptoms will appear. Some symptoms will manifest gradually during childhood.

- Failure to gain weight

- Failure to thrive

- Diarrhea

- Foul-smelling feces, steatorrhea

- Impaired nervous system functions

- Decreased reflexes, hyporeflexia