Infants born with congenital hypothyroidism may show no effects, or may display mild effects that often go unrecognized as a problem: excessive sleeping, reduced interest in nursing, poor muscle tone, low or hoarse cry, infrequent bowel movements, exaggerated jaundice, and low body temperature. If fetal deficiency was severe because of complete absence (athyreosis) of the gland, physical features may include a larger anterior fontanel, persistence of a posterior fontanel, an umbilical hernia, and a large tongue (macroglossia).

In the era before newborn screening, less than half of cases of severe hypothyroidism were recognized in the first month of life. As the months proceeded, these babies would grow poorly and be delayed in their development. By several years of age, they would display the recognizable facial and body features of cretinism. Persistence of severe, untreated hypothyroidism resulted in severe mental impairment, with an IQ below 80 in the majority. Most of these children eventually ended up in institutional care.

Around the world, the most common cause of congenital hypothyroidism is iodine deficiency, but in most of the developed world and areas of adequate environmental iodine, cases are due to a combination of known and unknown causes. Most commonly there is a defect of development of the thyroid gland itself, resulting in an absent (athyreosis) or underdeveloped (hypoplastic) gland. A hypoplastic gland may develop higher in the neck or even in the back of the tongue. A gland in the wrong place is referred to as "ectopic", and an ectopic gland at the base or back of the tongue is a "lingual" thyroid. Some of these cases of developmentally abnormal glands result from genetic defects, and some are "sporadic," with no identifiable cause. One Japanese study found a statistical correlation between certain organochlorine insecticides and dioxin-like chemicals in the milk of mothers who had given birth to infants with congenital hypothyroidism.

In some instances, hypothyroidism detected by screening may be transient. One common cause of this is the presence of maternal antibodies that temporarily impair thyroid function for several weeks.

Cretinism is an old term for the state of mental and physical retardation resulting from untreated congenital hypothyroidism, usually due to iodine deficiency from birth because of low iodine levels in the soil and local food sources. The term, like so many other 19th century medical terms, acquired pejorative connotations as it became used in lay speech. It is now rarely used by physicians.

Defined as those seen in any macrocytic, megaloblastic anemia:

- Anemia: causing fatigue, conjuctival pallor, pale complexion, and in some cases, a mild icterus (yellowing of the eye).

- Glossitis ("shiny tongue"): shiny, glossy tongue.

- Cheilosis (stomatitis): Inflammation of the edges of the lips and the oral mucosa.

- Tabes dorsalis ("subacute combined degeneration of the spinal cord"): This involves the posterior section of the spinal cord and therefore involves proprioception (sense of position), touch, sense of vibration and in severe cases the lateral corticospinal tract, causing spastic paralysis of the limbs.

- Peripheral neuropathy: tingling sensation in the arms and legs.

- Pancytopenia: decreased number of blood cells of all lineages (RBCs, leucocytes, platelets), due to decreased bone marrow production.

- Methylmalonyl CoA-emia: defined as blood having an unusually high concentration of methylmalonyl CoA.

- Peripheral findings such as hypersegmented neutrophils and large RBCs on high field view of the blood smears.

- Laboratory findings indicating increased MCV (Mean Corpuscular Volume), decreased Hgb/Hct (indicating anemia), and decreased value of vitamin B in the blood.

- Proteinuria: protein found in the urine detected by analysis or by dipstick.

- Reversal of all symptoms except neurological symptoms, by IV injection of vitamin B.

- Schilling test indicating no radioactive vitamin B in the urine. (This test has dropped out of favor and should not be tried in patients with any form of renal failure).

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.

Some patients suffering from copper deficiency have shown signs of vision and color loss. The vision is usually lost in the peripheral views of the eye. The bilateral vision loss is usually very gradual. An optical coherence tomography (OCT) shows some nerve fiber layer loss in most patients, suggesting the vision loss and color vision loss was secondary to optic neuropathy or neurodegeneration.

Imerslund–Gräsbeck syndrome, is a rare autosomal recessive, familial form of vitamin B deficiency caused by malfunction of the ""Cubam"" receptor located in the terminal ileum. This receptor is composed of two proteins, amnionless (AMN), and cubilin. A defect in either of these protein components can cause this syndrome. This is a rare disease, with a prevalence about 1 in 200,000, and is usually seen in patients of European ancestry.

Vitamin B is an important vitamin needed for bone marrow functioning, the deficit of which causes decreased marrow output and anemia. Vitamin B has two forms, one of which, along with folate, is important in DNA synthesis. Vitamin B is sensitive to acid deformation in the stomach, so a molecule called haptocorrin (R-factor), protects it in the stomach. In the small bowel, a molecule named intrinsic factor (IF), allows vitamin B to be absorbed in the ileum. IGS is caused by a mutation in the receptors located in the terminal portion of ileum. This is a very rare, and unlikely cause of vitamin B deficiency but is a cause nonetheless.

The acronym CHILD stands for the symptoms of the syndrome:

- CH = Congenital Hemidysplasia—One side of the body, most of the time the right side, is poorly developed. The right ribs, neck, vertebrae, etc. may be underdeveloped and the internal organs may be affected.

- I - Ichthyosiform Erythroderma—At birth or shortly after birth, there are red, inflamed patches (erythroderma), and flaky scales (ichthyosis) on the side of the body that is affected. Hair loss on the same side may also be possible.

- LD - limb defects—Fingers on the hand or toes on the foot of the affected side may be missing. An arm or leg may also be shortened or even missing.

Combined hyperlipidemia (or -aemia) (also known as multiple-type hyperlipoproteinemia) is a commonly occurring form of hypercholesterolemia (elevated cholesterol levels) characterised by increased LDL and triglyceride concentrations, often accompanied by decreased HDL. On lipoprotein electrophoresis (a test now rarely performed) it shows as a hyperlipoproteinemia type IIB. It is the most commonly inherited lipid disorder, occurring in around one in 200 persons. In fact, almost one in five individuals who develop coronary heart disease before the age of 60 have this disorder.

The elevated triglyceride levels (>5 mmol/l) are generally due to an increase in very low density lipoprotein (VLDL), a class of lipoproteins prone to cause atherosclerosis.

Acquired hyperlipidemias (also called secondary dyslipoproteinemias) often mimic primary forms of hyperlipidemia and can have similar consequences. They may result in increased risk of premature atherosclerosis or, when associated with marked hypertriglyceridemia, may lead to pancreatitis and other complications of the chylomicronemia syndrome. The most common causes of acquired hyperlipidemia are:

- diabetes mellitus

- Use of drugs such as thiazide diuretics, beta blockers, and estrogens

Other conditions leading to acquired hyperlipidemia include:

- Hypothyroidism

- Kidney failure

- Nephrotic syndrome

- Alcohol consumption

- Some rare endocrine disorders and metabolic disorders

Treatment of the underlying condition, when possible, or discontinuation of the offending drugs usually leads to an improvement in the hyperlipidemia.

Another acquired cause of hyperlipidemia, although not always included in this category, is postprandial hyperlipidemia, a normal increase following ingestion of food.

These unclassified forms are extremely rare:

- Hyperalphalipoproteinemia

- Polygenic hypercholesterolemia

The two forms of this lipid disorder are:

- Familial combined hyperlipidemia (FCH) is the familial occurrence of this disorder, probably caused by decreased LDL receptor and increased ApoB.

- Acquired combined hyperlipidemia is extremely common in patients who suffer from other diseases from the metabolic syndrome ("syndrome X", incorporating diabetes mellitus type II, hypertension, central obesity and CH). Excessive free fatty acid production by various tissues leads to increased VLDL synthesis by the liver. Initially, most VLDL is converted into LDL until this mechanism is saturated, after which VLDL levels elevate.

The defining characteristic of BPT is a tilting of an infant’s head in recurrent episodes, for varying periods of time. Furthermore, the child’s trunk may bend in the same direction as the head, giving the baby an overall curved shape; this complaint is known as tortipelvis. In addition to this, the individual may also, but not necessarily, experience vomiting, pallor, ataxia, agitation, infantile migraine, unsteadiness of gait upon learning to walk, general malaise and nystagmus.

The periods in which the child’s head is tilted and other symptoms appear can last anywhere from a few minutes to a few weeks, with a frequency of anywhere from two per year to two per month.

Congenital hemangioma can be distinguished from infantile hemangioma because it is fully developed at birth. It forms during prenatal life and has reached its maximal size at birth. Congenital hemangioma can even be diagnosed in utero by prenatal ultrasound. Unlike IH, CH is more common in the extremities, has an equal sex distribution, and is solitary, with an average diameter of 5 cm. It commonly presents in the head and neck and in the lower extremities.

Congenital hemangioma are divided into 2 subgroups: the rapidly involuting congenital hemangiomas (RICHs) and the non-involuting congenital hemangiomas(NICHs).

The rapidly involuting congenital hemangioma, RICH, presents at birth as a solitary raised tumor with a central depression, scar, or ulceration surrounded by a rim of pallor. It is noted for its involution, which typically begins several weeks after birth and is completed no later than 14 months of age. After regression RICH may cause a residual deformity, such as atrophic skin and subcutaneous tissue. It mainly affects the limbs (52%), but also the head and neck region (42%) and the trunk (6%).

The non-involuting congenital hemangioma, NICH, presents as a solitary, well-circumscribed reddish-pink to purple plaque with central telangiectasia and hypopigmented rim. In contrast to RICH, NICH does not involute and rarely ulcerates. It persists into late childhood and can even mimic a vascular malformation by growing commensurately with the child. Although NICH can resemble RICH in its external appearance, it can be differentiated from RICH by a greater elevation and coarse telangiectases. It mainly affects the head and neck region (43%), but also the limbs (38%) and the trunk (19%).

Surgical resection for congenital hemangiomas is rarely needed, because RICH undergoes postnatal regression and NICH is benign and often asymptomatic. Resection may be indicated to improve the appearance of the affected area, as long as the surgical scar is less noticeable than the lesion. Other indications are problematic ulcers with persistent bleeding or chronic infection.

Although most NICH lesions are non-problematic and do not cause significant deformity, the threshold for resection of NICH is lower, because it neither involutes, nor responds to pharmacotherapy. RICH tumors are observed until involution is completed. Involuted RICH may leave behind atrophic tissue, which can be reconstructed with autologous grafts. It is often best to postpone excision until regression is complete.

There are effective pharmacologic treatments, which include intralesional corticosteroid injection, systemic corticosteroid injection, interferon α-2a or α-2b and angiogenic inhibitors. The use of corticosteroids leads to accelerated regression in 30%, stabilization of growth in 40%, lightening of color and softening of the tumor. However, 30% shows minimal or no response. Another drug treatment is interferon α-2a or α-2b. It is often used for patients who did not respond to corticosteroids. Although the response rate is much slower, it has been successful for 80% of children treated. The most serious side effect of interferon is a spastic diplegia. Other therapeutic options are embolization and pulsed-dye laser, which improves residual telangiectasias in RICH and in NICH.

Vascular tumors, often referred to as hemangiomas, are the most common tumors in infants, occurring in 1-2%. Prevalence is even higher (10%) in premature infants of very low birth weight. Vascular tumors are characterized by overgrowth of normal vessels, which show increased endothelial proliferation. It can be present at birth, but often appears within a couple of weeks after birth or during infancy. There are different kinds of vascular tumors, but the 4 most common types are: infantile hemangioma, congenital hemangioma, kaposiform hemangioendothelioma and pyogenic granuloma.

Congenital hemidysplasia with ichthyosiform erythroderma and limb defects (also known as "CHILD syndrome") is a genetic disorder with onset at birth seen almost exclusively in females. The disorder is related to CPDX2, and also has skin and skeletal abnormalities, distinguished by a sharp midline demarcation of the ichthyosis with minimal linear or segmental contralateral involvement.

The acronym was introduced in 1980.

Benign paroxysmal torticollis (BPT) is a rare medical disorder affecting infants.

Malignant histiocytosis (also known as "Histiocytic medullary reticulosis") is a rare hereditary disease found in the Bernese Mountain Dog and humans, characterized by histiocytic infiltration of the lungs and lymph nodes. The liver, spleen, and central nervous system can also be affected. Histiocytes are a component of the immune system that proliferate abnormally in this disease. In addition to its importance in veterinary medicine, the condition is also important in human pathology.

The disease in the lungs is characterized by enlargement of the tracheobronchial lymph nodes and infiltration of the lungs, sometimes leading to lung lobe consolidation and pleural effusion. Signs and symptoms include cough, loss of appetite, weight loss, anemia, and difficulty breathing. Seizures and rear limb weakness can be seen. Invasion of the bone marrow can cause pancytopenia. Diagnosis requires a biopsy.

Repeated, periodic joint effusions of the knee. Usually one knee is affected but sometimes both knees. Other joints may also be involved along with the knee. Effusions are large, restricting range of motion but significant pain is not a feature. There is usually stiffness. Tenderness of the joint may or may not be present. Aspirated synovial fluid is usually sterile but will sometimes show elevated cell count (>100 cells/mL) with 50% being polymorphonuclear leukocytes.

Onset of effusions are sudden with no particular trigger or stimulus. Each episode lasts for a few days to about a week and recurs in cycles of 7 to 11 days with extremes of 3 days to 30 days also reported. Sometimes the joint may begin to swell again as soon as the fluid has subsided. Where both knees are affected concurrently, as one joint ceases to swell the other may become involved.

The cycle of joints swellings have been reported as being very regular, even predictable. This has been a characteristic feature of IH in many case reports. However, over the longer-term especially, these cycles of effusion and recovery may not be as constant as first reported.

In women, many cases seem to begin at puberty. Episodes of knee swelling may coincide the menstrual cycle. In nearly all case reports, pregnancy seems to suppress the condition but after birth, during lactation, it returns.

In the main, patients are mostly free of other symptoms. Fever is rare. There no signs of local inflammation or lymphatic involvement. Laboratory tests are generally normal or within reference limits.

Intermittent hydrarthrosis (IH), also known as "periodic synoviosis", "periodic benign synovitis", or "periodic hydrarthritis", is a chronic condition of unknown cause characterized by recurring, temporary episodes of fluid accumulation in the knee. While the knee is mainly involved, occasionally other joints such as the elbow or ankle can additionally be affected. Fluid accumulation in the joint can be extensive causing discomfort and impairing movement, although affected joints are not usually very painful. While the condition is chronic, it does not appear to progress to more destructive damage of the joint. It seems to affect slightly more women than men.

Episodes of swelling last several days or longer, can occur with regular or semi-regular frequency, typically one or two episodes per month. Between periods of effusion, knee swelling reduces dramatically providing largely symptomless intervals. Unlike some other rheumatological conditions such as rheumatoid arthritis, laboratory findings are usually within normal ranges or limits.

Clear treatment options have yet to be established. NSAIDs and COX2-inhibitors are generally not effective. Where this condition has been correctly diagnosed, various anti-rheumatic drugs as well as colchicine may be trialled to find the most effective option. More aggressive intra-articular treatment such chemical or radio-active synovectomy can also be helpful although benefits beyond 1 year have not been reported in literature.

The pain occurs only on one side of the head (unilateral), around the eye (orbital), particularly above the eye (supraorbital), in the temple (temporal), or in any combination.

The pain of CH attack is remarkably greater than in other headache conditions, including severe migraine. The pain is typically described as burning, stabbing, boring or squeezing, and may be located near or behind the eye. As a result of the pain, those with cluster headaches may experience suicidal thoughts during an attack (giving the alternative name "suicide headache" or "suicidal headache"). It is reported as one of the most painful conditions.

Cluster headaches are recurring bouts of excruciating unilateral headache attacks of extreme intensity. The duration of a typical CH attack ranges from about 15 to 180 minutes. Most untreated attacks (about 75%) last less than 60 minutes.

The onset of an attack is rapid and most often without preliminary signs that are characteristic in migraine. Preliminary sensations of pain in the general area of attack, referred to as "shadows", may signal an imminent CH, or these symptoms may linger after an attack has passed, or even between attacks. Though CH is strictly unilateral, there are some documented cases of "side-shift" between cluster periods, or, extremely rarely, simultaneous (within the same cluster period) bilateral cluster headaches.

Most speech sound disorders occur without a known cause. A child may not learn how to produce sounds correctly or may not learn the rules of speech sounds on his or her own. These children may have a problem with speech development, which does not always mean that they will simply outgrow it by themselves. Many children do develop speech sounds over time but those who do not often need the services of a Speech-Language Pathologist to learn correct speech sounds.

Some speech sound errors can result from other syndromes or disorders such as:

- developmental disorders (e.g. autism)

- genetic disorders (e.g. Down syndrome)

- hearing loss, including temporary hearing loss, such as from ear infections

- cleft palate or other physical anomalies of the mouth

- illness

- neurological disorders (e.g. cerebral palsy)

Transsexual people experience a gender identity that is inconsistent with, or not culturally associated with, their assigned sex, and desire to permanently transition to the gender with which they identify, usually seeking medical assistance (including hormone replacement therapy and other sex reassignment therapies) to help them align their body with their identified sex or gender.

"Transsexual" is generally considered a subset of "transgender", but some transsexual people reject the label of "transgender". A medical diagnosis of gender dysphoria can be made if a person expresses a desire to live and be accepted as a member of their identified sex, and if a person experiences impaired functioning or distress as a result of their gender identity.

A speech sound disorder is a speech disorder in which some speech sounds (called phonemes) in a child's (or, sometimes, an adult's) language are either not produced, not produced correctly, or are not used correctly. The term protracted phonological development is sometimes preferred when describing children's speech to emphasize the continuing development while acknowledging the delay.