Dual diagnosis (also called co-occurring disorders, COD, or dual pathology) is the condition of suffering from a mental illness and a comorbid substance abuse problem. There is considerable debate surrounding the appropriateness of using a single category for a heterogeneous group of individuals with complex needs and a varied range of problems. The concept can be used broadly, for example depression and alcoholism, or it can be restricted to specify severe mental illness (e.g. psychosis, schizophrenia) and substance misuse disorder (e.g. cannabis abuse), or a person who has a milder mental illness and a drug dependency, such as panic disorder or generalized anxiety disorder and is dependent on opioids. Diagnosing a primary psychiatric illness in substance abusers is challenging as drug abuse itself often induces psychiatric symptoms, thus making it necessary to differentiate between substance induced and pre-existing mental illness.

Those with co-occurring disorders face complex challenges. They have increased rates of relapse, hospitalization, homelessness, and HIV and hepatitis C infection compared to those with either mental or substance use disorders alone. The cause of co-occurring disorders is unknown, although there are several theories.

The identification of substance-induced versus independent psychiatric symptoms or disorders has important treatment implications and often constitutes a challenge in daily clinical practice. Similar patterns of comorbidity and risk factors in individuals with substance induced disorder and those with independent non-substance induced psychiatric symptoms suggest that the two conditions may share underlying etiologic factors.

Drug abuse, including alcohol and prescription drugs, can induce symptomatology which resembles mental illness, which can make it difficult to differentiate between substance induced psychiatric syndromes and pre-existing mental health problems. More often than not psychiatric disorders among drug or alcohol abusers disappear with prolonged abstinence. Substance induced psychiatric symptoms can occur both in the intoxicated state and also during the withdrawal state. In some cases these substance induced psychiatric disorders can persist long after detoxification, such as prolonged psychosis or depression after amphetamine or cocaine abuse. Abuse of hallucinogens can trigger delusional and other psychotic phenomena long after cessation of use and cannabis may trigger panic attacks during intoxication and with use it may cause a state similar to dysthymia. Severe anxiety and depression are commonly induced by sustained alcohol abuse which in most cases abates with prolonged abstinence. Even moderate sustained use of alcohol may increase anxiety and depression levels in some individuals. In most cases these drug induced psychiatric disorders fade away with prolonged abstinence. A protracted withdrawal syndrome can also occur with psychiatric and other symptoms persisting for months after cessation of use. Benzodiazepines are the most notable drug for inducing prolonged withdrawal effects with symptoms sometimes persisting for years after cessation of use.

Prospective epidemiological studies do not support the hypotheses that comorbidity of substance use disorders with other psychiatric illnesses is primarily a consequence of substance abuse or dependence or that increasing comorbidity is largely attributable to increasing use of substances. Yet emphasis is often on the effects of substances on the brain creating the impression that dual disorders are a natural consequence of these substances. However addictive drugs or exposure to gambling will not lead to addictive behaviors or drug dependence in most individuals but only in vulnerable ones, although, according to some researchers, neuroadaptation or regulation of neuronal plasticity, and molecular changes, may alter gene expression in some cases and subsequently lead to substance use disorders.

Research instruments are also often insufficiently sensitive to discriminate between independent, true dual pathology, and substance-induced symptoms. Structured instruments, as Global Appraisal of Individual Needs - Short Screener-GAIN-SS and Psychiatric Research Interview for Substance and Mental Disorders for DSM-IV-PRISM, have been developed to increase the diagnostic validity. While structured instruments can help organize diagnostic information, clinicians must still make judgments on the origin of symptoms.

The clinical manifestations present at birth are generalized hypotonia, muscle weakness, developmental delay with mental retardation and occasional seizures. The congenital muscular dystrophy is characterized by hypoglycosylation of α-dystroglycan.

Those born with the disease also experience severe ocular and brain defects. Half of all children with WWS are born with encephalocele, which is a gap in the skull that will not seal. The meninges of the brain protrude through this gap due to the neural tube failing to close during development. A malformation of the a baby's cerebellum is often a sign of this disease.Common ocular issues associated with WWS are abnormally small eyes and retinal abnormalities cause by an underdeveloped light-sensitive area in the back of the eye.

Walker–Warburg syndrome (WWS), also called Warburg syndrome, Chemke syndrome, HARD syndrome (Hydrocephalus, Agyria and Retinal Dysplasia), Pagon syndrome, cerebroocular dysgenesis (COD) or cerebroocular dysplasia-muscular dystrophy syndrome (COD-MD), is a rare form of autosomal recessive congenital muscular dystrophy. It is associated with brain (lissencephaly, hydrocephalus, cerebellar malformations) and eye abnormalities. This condition has a worldwide distribution. The overall incidence is unknown but a survey in North-eastern Italy has reported an incidence rate of 1.2 per 100,000 live births. It is the most severe form of congenital muscular dystrophy with most children dying before the age of three years.

Individuals with Refsum disease present with neurologic damage, cerebellar degeneration, and peripheral neuropathy. Onset is most commonly in childhood/adolescence with a progressive course, although periods of stagnation or remission occur. Symptoms also include ataxia, scaly skin (ichthyosis), difficulty hearing, and eye problems including retinitis pigmentosa, cataracts, and night blindness. In 80% of patients diagnosed with Refsum disease, sensorineural hearing loss has been reported. This is hearing loss as the result of damage to the inner ear or the nerve connected to ear to the brain.

Cemento-osseous dysplasia (COD) is a benign condition of the jaws that may arise from the fibroblasts of the periodontal ligaments. It is most common in African-American females. The three types are periapical cemental dysplasia (common in those of African descent), focal cemento-osseous dysplasia (Caucasians), and florid cemento-osseous dysplasia (African descent). Periapical occurs most commonly in the mandibular anterior teeth while focal appears predominantly in the mandibular posterior teeth and florid in both maxilla and mandible in multiple quadrants.

There is no treatment necessary for any type of COD. Diagnosis is important so that the treating doctor does not confuse it for another periapical disease such as rarefying osteitis or condensing osteitis. Incorrect diagnosis could lead to unnecessary root canal treatments. It can be diagnosed by radiographic appearance. Confirming the tooth is vital, as is noting the demographic (African American females).

After several months, untreated or inadequately treated patients may go on to develop severe and chronic symptoms that affect many parts of the body, including the brain, nerves, eyes, joints, and heart. Many disabling symptoms can occur, including permanent impairment of motor or sensory function of the lower extremities in extreme cases. The associated nerve pain radiating out from the spine is termed Bannwarth syndrome, named after Alfred Bannwarth.

The late disseminated stage is where the infection has fully spread throughout the body. Chronic neurologic symptoms occur in up to 5% of untreated patients. A polyneuropathy that involves shooting pains, numbness, and tingling in the hands or feet may develop. A neurologic syndrome called Lyme encephalopathy is associated with subtle cognitive difficulties, insomnia, a general sense of feeling unwell, and changes in personality. Other problems, however, such as depression and fibromyalgia, are no more common in people with Lyme disease than in the general population.

Chronic encephalomyelitis, which may be progressive, can involve cognitive impairment, brain fog, migraines, balance issues, weakness in the legs, awkward gait, facial palsy, bladder problems, vertigo, and back pain. In rare cases, untreated Lyme disease may cause frank psychosis, which has been misdiagnosed as schizophrenia or bipolar disorder. Panic attacks and anxiety can occur; also, delusional behavior may be seen, including somatoform delusions, sometimes accompanied by a depersonalization or derealization syndrome, where the patients begin to feel detached from themselves or from reality.

Lyme arthritis usually affects the knees. In a minority of patients, arthritis can occur in other joints, including the ankles, elbows, wrists, hips, and shoulders. Pain is often mild or moderate, usually with swelling at the involved joint. Baker's cysts may form and rupture. In some cases, joint erosion occurs.

"Acrodermatitis chronica atrophicans" (ACA) is a chronic skin disorder observed primarily in Europe among the elderly. ACA begins as a reddish-blue patch of discolored skin, often on the backs of the hands or feet. The lesion slowly atrophies over several weeks or months, with the skin becoming first thin and wrinkled and then, if untreated, completely dry and hairless.

Within days to weeks after the onset of local infection, the "Borrelia" bacteria may begin to spread through the bloodstream. EM may develop at sites across the body that bear no relation to the original tick bite. Another skin condition, apparently absent in North American patients, but found in Europe, is borrelial lymphocytoma, a purplish lump that develops on the ear lobe, nipple, or scrotum.

Various acute neurological problems, termed neuroborreliosis, appear in 10–15% of untreated people. These include facial palsy, which is the loss of muscle tone on one or both sides of the face, as well as meningitis, which involves severe headaches, neck stiffness, and sensitivity to light. Inflammation of the spinal cord's nerve roots can cause shooting pains that may interfere with sleep, as well as abnormal skin sensations. Mild encephalitis may lead to memory loss, sleep disturbances, or mood changes. In addition, some case reports have described altered mental status as the only symptom seen in a few cases of early neuroborreliosis. The disease may adversely impact the heart's electrical conduction system and can cause abnormal heart rhythms such as atrioventricular block.

The signs and symptoms of allergies in a child are:

- Chronic symptoms resembling the cold that last more than a week or two.

- Cold-like symptoms that appear during the same time each year

- Repeated difficulty breathing, wheezing and breathing

- Cold-like symptoms that happen at night

- Cold-like symptoms that happen during exercise

- Chronic rashes or patches of skin that are dry, itchy, look like scales

- Cold-like symptoms that appear after eating a certain food

- Hives

- Swelling of face, arms or legs

- Gagging, coughing or wheezing, vomiting or significant abdominal pain

- Itching or tingling sensations in the mouth, throat or ears

Refsum disease, also known as classic or adult Refsum disease, heredopathia atactica polyneuritiformis, phytanic acid oxidase deficiency and phytanic acid storage disease, is an autosomal recessive neurological disease that results from the over-accumulation of phytanic acid in cells and tissues. It is one of several disorders named after Norwegian neurologist Sigvald Bernhard Refsum (1907–1991). Refsum disease typically is adolescent onset and is diagnosed by above average levels of phytanic acid. Humans obtain the necessary phytanic acid primarily through diet. It is still unclear what function phytanic acid plays physiologically in humans, but has been found to regulate fatty acid metabolism in the liver of mice.

Cat skin disorders are among the most common health problems in cats.

Skin disorders in cats have many causes, and many of the common skin disorders that afflict people have a counterpart in cats. The condition of a cat's skin and coat can also be an important indicator of its general health. Skin disorders of cats vary from acute, self-limiting problems to chronic or long-lasting problems requiring life-time treatment. Cat skin disorders may be grouped into categories according to the causes.

Rheumatism or rheumatic disorder is an umbrella term for conditions causing

chronic, often intermittent pain affecting the joints and/or connective tissue.

The study of, and therapeutic interventions in, such disorders is called rheumatology.

The term "rheumatism", however, does not designate any specific disorder, but covers at least 200 different conditions.

Sources dealing with rheumatism tend to focus on arthritis, but "rheumatism" may also refer to other conditions causing chronic pain, grouped as "non-articular rheumatism", also known as "regional pain syndrome" or "soft tissue rheumatism". The term "Rheumatic Diseases" is used in MeSH to refer to connective tissue disorders.

Keshan disease is a congestive cardiomyopathy caused by a combination of dietary deficiency of selenium and the presence of a mutated strain of Coxsackievirus, named after Keshan County of Heilongjiang province, Northeast China, where symptoms were first noted. These symptoms were later found prevalent in a wide belt extending from northeast to southwest China, all due to selenium-deficient soil. The disease peaked in 1960–1970, claiming thousands of lives.

Often fatal, the disease afflicts children and women of child bearing age, characterized by heart failure and pulmonary edema. Over decades, supplementation with selenium reduced this affliction.

It had been linked to the coxsackie B virus. Current research suggests that the lack of selenium results in a more virulent strain of the coxsackievirus becoming the dominant viral species present in the population of virus, but the mechanism of this selection event is unclear.

The disease got its name from the province in which it was discovered: Keshan, China. Since its discovery, it can also be found in New Zealand and Finland. Keshan disease results from a selenium deficiency which is a nutrient we receive in our diet from eating foods that were grown in selenium enriched soils. Because of that factor, Keshan deficiency can be found anywhere that the level of selenium present in the soil is low. An individual with Keshan disease will have an abnormally large heart. Keshan disease can also lead to higher rates of cancer, cardiovascular disease, hypertension, and strokes. In addition, an individual can experience eczema, psoriasis, arthritis, cataracts, alcoholism, and infections.

Skin disease may result from deficiencies in immune system function. In cats, the most common cause of immune deficiency is infection with retroviruses, FIV or FeLV, and cats with these chronic infections are subject to repeated bouts of skin infection and abscesses. This category also includes hypersensitivity disorders and eosinophilic skin diseases such as atopic dermatitis, miliary dermatitis and feline eosinophilic granuloma and skin diseases caused by autoimmunity, such as pemphigus and discoid lupus.

Angular cheilitis is a fairly non specific term which describes the presence of an inflammatory lesion in a particular anatomic site (i.e. the corner of the mouth). As there are different possible causes and contributing factors from one person to the next, the appearance of the lesion is somewhat variable. The lesions are more commonly symmetrically present on both sides of the mouth, but sometimes only one side may be affected. In some cases, the lesion may be confined to the mucosa of the lips, and in other cases the lesion may extend past the vermilion border (the edge where the lining on the lips becomes the skin on the face) onto the facial skin. Initially, the corners of the mouth develop a gray-white thickening and adjacent erythema (redness). Later, the usual appearance is a roughly triangular area of erythema, edema (swelling) and breakdown of skin at either corner of the mouth. The mucosa of the lip may become fissured (cracked), crusted, ulcerated or atrophied. There is not usually any bleeding. Where the skin is involved, there may be radiating rhagades (linear fissures) from the corner of the mouth. Infrequently, the dermatitis (which may resemble eczema) can extend from the corner of the mouth to the skin of the cheek or chin. If "Staphylococcus aureus" is involved, the lesion may show golden yellow crusts. In chronic angular cheilitis, there may be suppuration (pus formation), exfoliation (scaling) and formation of granulation tissue.

Sometimes contributing factors can be readily seen, such as loss of lower face height from poorly made or worn dentures, which results in mandibular overclosure ("collapse of jaws"). If there is a nutritional deficiency underlying the condition, various other signs and symptoms such as glossitis (swollen tongue) may be present. In people with angular cheilitis who wear dentures, often there may be erythematous mucosa underneath the denture (normally the upper denture), an appearance consistent with denture-related stomatitis. Typically the lesions give symptoms of soreness, pain, pruritus (itching) or burning or a raw feeling.

Allergies in children are those causes, pathophsiology, treatments, management, practices and control of allergies that develop in children. Up to 40 percent of children suffer from allergic rhinitis. And children are more likely to develop allergies if one or both parents have allergies. Allergies differ between adults and children. Part of the reason for this that the respiratory system in children is smaller. The bronchi and bronchioles are narrower so even a slight decrease in diameter of these airways can have serious consequences. In addition, children often 'outgrow' their allergies.

The incidence of childhood allergies has increased in the past 50 years.

Several different nutritional deficiency states of vitamins or minerals have been linked to AC. It is thought that in about 25% of people with AC, iron deficiency or deficiency of B vitamins are involved. Nutritional deficiencies may be a more common cause of AC in Third World countries. Chronic iron deficiency may also cause koilonychia (spoon shaped deformity of the fingernails) and glossitis (inflammation of the tongue). It is not completely understood how iron deficiency causes AC, but it is known that it causes a degree of immunocompromise (decreased efficiency of the immune system) which may in turn allow an opportunistic infection of candida. Vitamin B2 deficiency (ariboflavinosis) may also cause AC, and other conditions such as redness of mucous membranes, magenta colored glossitis (pink inflammation of the tongue). Vitamin B5 deficiency may also cause AC, along with glossitis, and skin changes similar to seborrhoeic dermatitis around the eyes, nose and mouth. Vitamin B12 deficiency is sometimes responsible for AC, and commonly occurs together with folate deficiency (a lack of folic acid), which also causes glossitis and megaloblastic anemia. Vitamin B3 deficiency (pellagra) is another possible cause, and in which other association conditions such as dermatitis, diarrhea, dementia and glossitis can occur. Biotin (vitamin B7) deficiency has also been reported to cause AC, along with hair loss (alopecia) and dry eyes. Zinc deficiency is known to cause AC. Other symptoms may include diarrhea, alopecia and dermatitis. Acrodermatitis enteropathica is an autosomal recessive genetic disorder causing impaired absorption of zinc, and is associated with AC.

In general, these nutritional disorders may be caused by malnutrition, such as may occur in alcoholism or in poorly considered diets, or by malabsorption secondary to gastrointestinal disorders (e.g. Coeliac disease or chronic pancreatitis) or gastrointestinal surgeries (e.g. pernicious anemia caused by ileal resection in Crohn's disease).

There are two ways in which the virus can progress, systematic and encephalitic, depending on the person's age. Encephalitic involves swelling of the brain and can be asymptomatic while the systemic illness occurs very abruptly. Those with the systemic illness usually recover within one to two weeks. While the encephalitis is more common among infants in adults and children it usually manifests after experiencing the systemic illness. Symptoms include high fever, muscle pain, altered mental status, headache, meningeal irritation, photophobia, and seizures, which occur three to 10 days after the bite of an infected mosquito. Due to the virus's effect on the brain, patients who survive can be left with mental and physical impairments such as personality disorders, paralysis, seizures, and intellectual impairment

The common cause of blindness in developing countries is VAD. The WHO estimates 13.8 million children to have some degree of visual loss related to VAD. Night blindness and its worsened condition, xerophthalmia, are markers of VAD, as it can also lead to impaired immune function, cancer, and birth defects. Collections of keratin in the conjunctiva, known as Bitot's spots, are also seen. Imtiaz's sign is the earliest ocular sign of VAD. Conjunctival epithelial defects occur around lateral aspect of the limbus in the subclinical stage of VAD. These conjunctival epithelial defects are not visible on a biomicroscope, but they take up black stain and become readily visible after instillation of kajal (surma); this is called "Imtiaz's sign". Vitamin A deficiency is one of several hypovitaminoses implicated in follicular hyperkeratosis.

Many rheumatic disorders of chronic, intermittent joint pain have historically been caused by infectious diseases. Their etiology was unknown until the 20th century and not treatable, like Lyme disease (in the Northern and Northeastern US), coccidiomycosis or Valley fever (in the Western US), and Chikungunya in India and a myriad of causes for postinfectious arthritis also known as reactive arthritis like, for example, the once very common rheumatic fever after Group A Streptococcus infection up to the rare Whipple's disease.

Major rheumatic disorders currently recognized include

- Back pain

- Bursitis/Tendinitis of the shoulder, wrist, biceps, leg, knee cap (patella), ankle, hip, and Achilles tendon

- Capsulitis

- Neck pain

- Osteoarthritis

- Palindromic rheumatism has been theorized to be a form of rheumatoid arthritis.

Although these disorders probably have little in common in terms of their epidemiology, they do share three characteristics: they cause chronic, often intermittent pain, they are difficult to treat and are collectively very common.

Rheumatic diseases caused by autoimmunity include:

- Ankylosing spondylitis

- relapsing polychondritis

- systemic lupus erythematosus

- rheumatoid arthritis

- gout, inflammatory arthritis, pseudogout

- juvenile arthritis

- Sjögren syndrome

- scleroderma

- Polymyositis

- Dermatomyositis

- Behçet's disease

- Psoriatic arthritis

Eastern equine encephalitis (EEE), commonly called Triple E or, sleeping sickness (not to be confused with "Trypanosomiasis") is a zoonotic alphavirus and arbovirus present in North, Central and South America and the Caribbean. EEE was first recognized in Massachusetts, United States in 1831 when 75 horses died mysteriously of viral encephalitis.

Epizootics in horses have continued to occur regularly in the United States. It can also be identified in asses and zebras. Due to the rarity of the disease its occurrence can cause economic impact in relation to the loss of horses and poultry. EEE is found today in the eastern part of the country and is often associated with coastal plains. It can most commonly be found in east and gulf coast states. In Florida about one to two human cases are reported a year although over sixty cases of equine encephalitis are reported. Some years in which there are favorable conditions for the disease there number of equine cases are over two-hundred. Diagnosing equine encephalitis is challenging because many of the symptoms are shared with other illnesses and patients can be asymptomatic. Confirmations may require a sample of cerebral spinal fluid or brain tissue although CT scans and MRI scans are used to detect encephalitis. This could be an indication that the need to test for Eastern Equine Encephalitis is necessary. If a biopsy of the cerebral spinal fluid is taken it is sent to a specialized laboratory for testing.

EEEV is closely related to Venezuelan equine encephalitis virus and Western equine encephalitis virus.

Vitamin A deficiency (VAD) or hypovitaminosis A is a lack of vitamin A in blood and tissues. It is common in poorer countries, but rarely is seen in more developed countries. Nyctalopia (night blindness) is one of the first signs of VAD. Xerophthalmia, keratomalacia, and complete blindness can also occur since vitamin A has a major role in phototransduction. The three forms of vitamin A include retinols, beta-carotenes, and carotenoids.

Vitamin A deficiency is the leading cause of preventable childhood blindness, and is critical to achieving Millennium Development Goal 4 to reduce child mortality. About 250,000 to 500,000 malnourished children in the developing world go blind each year from a deficiency of vitamin A, around half of whom die within a year of becoming blind. The United Nations Special Session on Children in 2002 set a goal of the elimination of VAD by 2010.

The prevalence of night blindness due to VAD is also high among pregnant women in many developing countries. VAD also contributes to maternal mortality and other poor outcomes in pregnancy and lactation.

VAD also diminishes the ability to fight infections. In countries where children are not immunized, infectious diseases such as measles have higher fatality rates. As elucidated by Alfred Sommer, even mild, subclinical deficiency can also be a problem, as it may increase children's risk of developing respiratory and diarrheal infections, decrease growth rate, slow bone development, and decrease likelihood of survival from serious illness.

VAD is estimated to affect about one-third of children under the age of five around the world. It is estimated to claim the lives of 670,000 children under five annually. Around 250,000–500,000 children in developing countries become blind each year owing to VAD, with the highest prevalence in Southeast Asia and Africa. According to the World Health Organization (WHO), VAD is under control in the United States, but in developing countries, VAD is a significant concern. Globally, 65% of all children aged 6 to 59 months received two doses of vitamin A in 2013, fully protecting them against VAD (80% in the least developed countries).

Signs and symptoms of rickets can include bone tenderness, and a susceptibility for bone fractures particularly greenstick fractures. Early skeletal deformities can arise in infants such as soft, thinned skull bones – a condition known as craniotabes which is the first sign of rickets; skull bossing may be present and a delayed closure of the fontanelles.

Young children may have bowed legs and thickened ankles and wrists; older children may have knock knees. Spinal curvatures of kyphoscoliosis or lumbar lordosis may be present. The pelvic bones may be deformed. A condition known as rachitic rosary can result as the thickening caused by nodules forming on the costochondral joints. This appears as a visible bump in the middle of each rib in a line on each side of the body. This somewhat resembles a rosary, giving rise to its name. The deformity of a pigeon chest may result in the presence of Harrison's groove.

Hypocalcemia, a low level of calcium in the blood can result in tetany – uncontrolled muscle spasms. Dental problems can also arise.

An X-ray or radiograph of an advanced sufferer from rickets tends to present in a classic way: the bowed legs (outward curve of long bone of the legs) and a deformed chest. Changes in the skull also occur causing a distinctive "square headed" appearance known as "caput quadratum". These deformities persist into adult life if not treated. Long-term consequences include permanent curvatures or disfiguration of the long bones, and a curved back.

It is hard to consider Keshan disease extremely preventable because the only way to ensure that the individual is getting enough selenium would be to test the soil in the area. However, one way that selenium intake can be improved is to increase intake of foods that are rich with selenium. Examples include onions, canned tuna, beef, cod, turkey, chicken breast, enriched pasta, egg, cottage cheese, oatmeal, white or brown rice, and garlic. If the individual lives in an area that does not have selenium enriched soil, dietary supplementation should be considered. To determine whether or not an individual is selenium deficient, blood testing is performed.