Trimethylamine builds up in the bodies of patients with trimethylaminuria. The trimethylamine is released in the person's sweat, urine, reproductive fluids, and breath, giving off a strong fishy or body odor. Some people with trimethylaminuria have a strong odor all the time, but most have a moderate smell that varies in intensity over time. Individuals with this condition do not have any physical symptoms, and they typically appear healthy.

The condition seems to be more common in women than men, for unknown reasons. Scientists suspect that such female sex hormones as progesterone and estrogen aggravate the condition. According to several reports, the condition worsens around puberty. In women, symptoms may worsen just before and during menstrual periods, after taking oral contraceptives, and around menopause.

The odor seems to vary depending on many known factors, including diet, hormonal changes, stress level, amount of sweat, other odors in the space, and the observer's sense of smell.

Trimethylaminuria (TMAU; primary trimethylaminuria), also known as fish odor syndrome or fish malodor syndrome, is a rare metabolic disorder that causes a defect in the normal production of an enzyme named flavin-containing monooxygenase 3 ("FMO3"). When "FMO3" is not working correctly or if not enough enzyme is produced, the body loses the ability to properly convert trimethylamine (TMA) from precursor compounds in food digestion into trimethylamine oxide (TMAO), through a process called "N"-oxidation. Trimethylamine then builds up and is released in the person's sweat, urine, and breath, giving off a strong fishy odor or strong body odor. A variant of TMAU (secondary trimethylaminuria or TMAU2) exists where there is no genetic cause, yet excessive TMA is secreted, possibly due to intestinal dysbiosis, altered metabolism, or hormonal causes.

Infants with this disease seem healthy at birth but quickly deteriorate, often with severe brain damage, which may be permanent. Death often occurs within the first five months in severe cases of the disease, when left untreated.

The disease is named for the presence of sweet-smelling urine, an odor similar to that of maple syrup, when the person goes into metabolic crisis. The smell is also present and sometimes stronger in the ear wax of an affected individual at these times. In populations to whom maple syrup is unfamiliar, the aroma can be likened to fenugreek, and fenugreek ingestion may impart the aroma to urine.

A characteristic feature of isovaleric acidemia is a distinctive odor of sweaty feet. This odor is caused by the buildup of a compound called isovaleric acid in affected individuals.

In about half of cases, the signs and symptoms of this disorder become apparent within a few days after birth and include poor feeding, vomiting, seizures, and lack of energy that can progress to coma. These medical problems are typically severe and can be life-threatening. In the other half of cases, the signs and symptoms of the disorder appear during childhood and may come and go over time. They are often triggered by an infection or by eating an increased amount of protein-rich foods.

Isovaleric acidemia is a rare autosomal recessive metabolic disorder which disrupts or prevents normal metabolism of the branched-chain amino acid leucine. It is a classical type of organic acidemia.

Untreated PKU can lead to intellectual disability, seizures, behavioral problems, and mental disorders. It may also result in a musty smell and lighter skin. Babies born to mothers who have poorly treated PKU may have heart problems, a small head, and low birth weight.

Because the mother's body is able to break down phenylalanine during pregnancy, infants with PKU are normal at birth. The disease is not detectable by physical examination at that time, because no damage has yet been done. However, a blood test can reveal elevated phenylalanine levels after one or two days of normal infant feeding. This is the purpose of newborn screening, to detect the disease with a blood test before any damage is done, so that treatment can prevent the damage from happening.

If a child is not diagnosed during the routine newborn screening test (typically performed 2–7 days after birth, using samples drawn by neonatal heel prick), and a phenylalanine restricted diet is not introduced, then phenylalanine levels in the blood will increase over time. Toxic levels of phenylalanine (and insufficient levels of tyrosine) can interfere with infant development in ways which have permanent effects. The disease may present clinically with seizures, hypopigmentation (excessively fair hair and skin), and a "musty odor" to the baby's sweat and urine (due to phenylacetate, a carboxylic acid produced by the oxidation of phenylketone). In most cases, a repeat test should be done at approximately two weeks of age to verify the initial test and uncover any phenylketonuria that was initially missed.

Untreated children often fail to attain early developmental milestones, develop microcephaly, and demonstrate progressive impairment of cerebral function. Hyperactivity, EEG abnormalities, and seizures, and severe learning disabilities are major clinical problems later in life. A characteristic "musty or mousy" odor on the skin, as well as a predisposition for eczema, persist throughout life in the absence of treatment.

The damage done to the brain if PKU is untreated during the first months of life is not reversible. It is critical to control the diet of infants with PKU very carefully so that the brain has an opportunity to develop normally. Affected children who are detected at birth and treated are much less likely to develop neurological problems or have seizures and intellectual disability (though such clinical disorders are still possible.)

In general, however, outcomes for people treated for PKU are good. Treated people may have no detectable physical, neurological, or developmental problems at all. Many adults with PKU who were diagnosed through newborn screening and have been treated since birth have high educational achievement, successful careers, and fulfilling family lives.

Symptoms of the familial form include visual impairment caused by diffuse corneal opacities, target cell hemolytic anemia, and renal failure. Less common symptoms include atherosclerosis, hepatomegaly (enlarged liver), splenomegaly (enlarged spleen), and lymphadenopathy.

Fish-eye disease is less severe and most commonly presents with impaired vision due to corneal opacification. It rarely presents with other findings, although, atherosclerosis, hepatomegaly, splenomegaly, and lymphadenopathy can occur. Carlson and Philipson found that the disease was named so because the cornea of the eye was so opaque or cloudy with dots of cholesterol that it resembled a boiled fish.

If an individual only carry one copy of the mutated gene, they typically do not show symptoms.

Type 1 tyrosinemia typically presents in infancy as failure to thrive and hepatomegaly. The primary effects are progressive liver and kidney dysfunction. The liver disease causes cirrhosis, conjugated hyperbilirubinemia, elevated AFP, hypoglycemia and coagulation abnormalities. This can lead to jaundice, ascites and hemorrhage. There is also an increased risk of hepatocellular carcinoma.

The kidney dysfunction presents as Fanconi syndrome: Renal tubular acidosis, hypophosphatemia and aminoaciduria. Cardiomyopathy, neurologic and dermatologic manifestations are also possible. The urine has an odor of cabbage or rancid butter.

Type 1 tyrosinemia, also known as hepatorenal tyrosinemia or tyrosinosis, is the most severe form of tyrosinemia, a buildup of too much of the amino acid tyrosine in the blood and tissues due to an inability to metabolize it. It is caused by a deficiency of the enzyme fumarylacetoacetate hydrolase.

Phenylketonuria (PKU) is an inborn error of metabolism that results in decreased metabolism of the amino acid phenylalanine. Untreated PKU can lead to intellectual disability, seizures, behavioral problems, and mental disorders. It may also result in a musty smell and lighter skin. Babies born to mothers who have poorly treated PKU may have heart problems, a small head, and low birth weight.

Phenylketonuria is a genetic disorder inherited from a person's parents. It is due to mutations in the "PAH" gene which results in low levels of the enzyme phenylalanine hydroxylase. This results in the buildup of dietary phenylalanine to potentially toxic levels. It is autosomal recessive meaning that both copies of the gene must be mutated for the condition to develop. There are two main types, classic PKU and variant PKU, depending on if any enzyme function remains. Those with one copy of a mutated gene typically do not have symptoms. Many countries have newborn screening programs for the disease.

Treatment is with a diet low in foods that contain phenylalanine and special supplements. Babies should use a special formula. The diet should begin as soon as possible after birth and will be lifelong. People who are diagnosed early and maintain a strict diet can have normal health and a normal life span. Effectiveness is monitored through periodic blood tests. The medication sapropterin dihydrochloride may be useful in some.

Phenylketonuria affects about one in 12,000 babies. Males and females are affected equally. The disease was discovered in 1934 by Ivar Asbjørn Følling with the importance of diet determined in 1953. Gene therapy, while promising, requires a great deal more study as of 2014.

Lecithin cholesterol acyltransferase deficiency (LCAT deficiency) is a disorder of lipoprotein metabolism. The disease has two forms: Familial LCAT deficiency, in which there is complete LCAT deficiency, and Fish-eye disease, in which there is a partial deficiency.

Lecithin cholesterol acyltransferase catalyzes the formation of cholesterol esters in lipoproteins.

Fancy goldfish are among the fish most commonly affected by this disorder. The disease may be caused by intestinal parasites or by constipation induced by high nitrate levels from over feeding.

Body odor (American English) or body odour (British English; see spelling differences) is present in animals and humans, and its intensity can be influenced by many factors (behavioral patterns, survival strategies). Body odor has a strong genetic basis both in animals and humans, but it can be also strongly influenced by various diseases and physiological conditions. Body odor is generally considered to be an unpleasant odor among many human cultures.

Swim bladder disease, also called swim bladder disorder or flipover, is a common ailment in aquarium fish. The swim bladder is an internal gas-filled organ that contributes to the ability of a fish to control its buoyancy, and thus to stay at the current water depth without having to waste energy in swimming. A fish with swim bladder disorder can float nose down tail up, or can float to the top or sink to the bottom of the aquarium.

Physical Symptoms

- Heart Defects

- Characteristics of Autism

- Genital defects (in males)

- Childhood hypotonia

- Respiratory infections

- Motor Delay

- Renal defects

Behavioural Symptoms

- Passiveness

- Sociability

- Aggression

- Biting, and/or hitting

- Moodiness

- Disliking routine changes

The first signs of poisoning suggest an allergic reaction with the following symptoms:

- facial flushing/sweating

- burning-peppery taste sensations in the mouth and throat

- dizziness

- nausea

- headache

- tachycardia

- cold-like symptoms

The earliest signs and symptoms occur in newborns and consist of hypotonia, but show up in youth as developmental delays, low muscle tone, learning disabilities, being overweight, autism-like symptoms, seizures, eczema, asthma, chest and ear infections, and abnormalities in face, hands, and feet. Autism-like symptoms consist of odd obsessions, repetitive behavior, poor use of eye contact, impaired speech, poor understanding of others’ emotions, idiosyncratic use of words or phrases. People with this disorder also tend to have a characteristic appearance, including prominent forehead, thin, highly arched eyebrows, depressed nasal bridge, full cheeks, deficient nasal alae and prominent columella, thin upper lip, and various minor anomalies of the pinnae. Heart, brain, gastrointestinal, and kidney problems such as Wilms tumor, hernias, spinal curvatures, Osteopenia, hearing and sight difficulties can also occur.

It has been associated with Wilms' tumor and brachydactyly.

The above symptoms can advance to:

- facial rash (intense itching may accompany the rash.)

- torso or body rash: The rash associated with scombroid poisoning is a form of urticaria, but most commonly does not include wheals (patchy areas of skin-swelling also known as hives) that may be seen in true allergies.

- edema (this is generalized if it occurs at all)

- short-term diarrhea

- abdominal cramps

The most common characteristics include a distinct craniofacial phenotype (microcephaly, micrognathia, short philtrum, prominent glabella, ocular hypertelorism, dysplastic ears and periauricular tags), growth restriction, intellectual disability, muscle hypotonia, seizures, and congenital heart defects. Less common characteristics include hypospadias, colobomata of the iris, renal anomalies, and deafness. Antibody deficiencies are also common, including common variable immunodeficiency and IgA deficiency. T-cell immunity is normal.

Wolf–Hirschhorn syndrome (WHS), also known as chromosome deletion Dillan 4p syndrome, Pitt–Rogers–Danks syndrome (PRDS) or Pitt syndrome, was first described in 1961 by Americans Herbert L. Cooper and Kurt Hirschhorn and, thereafter, gained worldwide attention by publications by the German Ulrich Wolf, and Hirschhorn and their co-workers, specifically their articles in the German scientific magazine "Humangenetik". It is a characteristic phenotype resulting from a partial deletion of chromosomal material of the short arm of chromosome 4 (del(4p16.3)).

2q37 deletion syndrome is a disorder caused by the deletion of a small piece of chromosome 2.2q37 deletion syndrome describes a disorder in which one or multiple of 3 sub-bands, 2q37.1, 2q37.2, and 2q37.3, of the last band of one of the chromosome 2’s long arms are deleted. The first report of this disorder was in 1989.

Head and lateral line erosion, (HLLE) or hole-in-the-head (HITH) is a disease in fish. Chronic ulcerative dermatopathy or chronic erosive dermatopathy are symptoms of similar conditions with different etiology.

HLLE begins as small pits of receding epithelium (skin) around the fish’s head and/or lateral line, and sometimes onto the unpaired fins. Rarely fatal, it does cause disfigurement, making the fish less suitable for public aquarium display. At least 20 families of fish have been identified as having developed HLLE in captivity. Not all species of fish show the same symptoms, and do not always develop lesions to the same degree.

Diseases can have a variety of causes, including bacterial infections from an external source such as "Pseudomonas fluorescens" (causing fin rot and fish dropsy), fungal infections (Saprolegnia), mould infections (Oomycete and "Saprolegnia"), parasitic disorders ("Gyrodactylus salaris", "Ichthyophthirius multifiliis", Cryptocaryon, Oodinium causing velvet disease, "Brooklynella hostilis", head and lateral line erosion, Glugea, "Ceratomyxa shasta", "Kudoa thyrsites", "Tetracapsuloides bryosalmonae", "Ceratomyxa shasta" leeches, nematode, Trematoda, Platyhelminthes and fish louse), viral disorders, metabolic disorders, inappropriate water conditions (insufficient aeration, pH, water hardness, temperature and ammonia poisoning) and malnutrition.

External bacterial infections may cause spots or streaks on the body which appear red or orange Dropsy (bloating) is also a sign of a bacterial infection. "False fungal infections" look like fungus but is actually a bacterial infection known as Columnaris. These symptoms may include a white or gray film on the body.