Dyschromatosis symmetrica hereditaria (also known as "reticulate acropigmentation of Dohi", and "symmetrical dyschromatosis of the extremities") is a rare autosomally inherited dermatosis. It is characterized by progressively pigmented and depigmented macules, often mixed in a reticulate pattern, concentrated on the dorsal extremities. It presents primarily in the Japanese, but has also been found to affect individuals from Europe, India and the Caribbean.

Age: The mucocutaneous features of DKC typically develop between ages 5 and 15 years. The median age of onset of the peripheral cytopenia is 10 years.

Sex: The male-to-female ratio is approximately 3:1.

Physical: The triad of reticulated hyperpigmentation of the skin, nail dystrophy, and leukoplakia characterizes DKC. The syndrome is clinically heterogeneous; in addition to the diagnostic mucocutaneous features and bone marrow failure, affected individuals can have a variety of other clinical features.

Cutaneous findings:

The primary finding is abnormal skin pigmentation, with tan-to-gray hyperpigmented or hypopigmented macules and patches in a mottled or reticulated pattern. Reticulated pigmentation occurs in approximately 90% of patients. Poikilodermatous changes with atrophy and telangiectasia are common.

The cutaneous presentation may clinically and histologically resemble graft versus host disease. The typical distribution involves the sun-exposed areas, including the upper trunk, neck, and face. Other cutaneous findings may include alopecia of the scalp, eyebrows, and eyelashes; premature graying of the hair; hyperhidrosis; hyperkeratosis of the palms and soles; and adermatoglyphia (loss of dermal ridges on fingers and toes).

Nail findings:

Nail dystrophy is seen in approximately 90% of patients, with fingernail involvement often preceding toenail involvement.

Progressive nail dystrophy begins with ridging and longitudinal splitting. Progressive atrophy, thinning, pterygium, and distortion eventuate in small, rudimentary, or absent nails.

Mucosal findings:

Mucosal leukoplakia occurs in approximately 80% of patients and typically involves the buccal mucosa, tongue, and oropharynx. The leukoplakia may become verrucous, and ulceration may occur. Patients also may have an increased prevalence and severity of periodontal disease.

Other mucosal sites may be involved (e.g., esophagus, urethral meatus, glans penis, lacrimal duct, conjunctiva, vagina, anus). Constriction and stenosis can occur at these sites, with subsequent development of dysphagia, dysuria, phimosis, and epiphora.

Bone marrow failure:

Approximately 90% have peripheral cytopenia of one or more lineages. In some cases, this is the initial presentation, with a median age of onset of 10 years.

Bone marrow failure is a major cause of death, with approximately 70% of deaths related to bleeding and opportunistic infections as a result of bone marrow failure.

Pulmonary complications:

Approximately 20% of individuals with DKC develop pulmonary complications, including pulmonary fibrosis and abnormalities of pulmonary vasculature.

The recommendation is that DKC patients avoid taking drugs with pulmonary toxicity (e.g., busulfan) and that they have their lungs shielded from radiation during BMT.

Increased risk of malignancy:

Patients have an increased prevalence of malignant mucosal neoplasms, particularly squamous cell carcinoma of the mouth, nasopharynx, esophagus, rectum, vagina, or cervix. These often occur within sites of leukoplakia.

The prevalence of squamous cell carcinoma of the skin is also increased. Other malignancies reported include Hodgkin lymphoma, adenocarcinoma of the gastrointestinal tract, and bronchial and laryngeal carcinoma.

Malignancy tends to develop in the third decade of life.

Neurologic system findings: Patients may have learning difficulties and mental retardation.

Ophthalmic system findings: DKC reportedly is associated with conjunctivitis, blepharitides, and pterygium. Lacrimal duct stenosis resulting in epiphora (i.e., excessive tearing) occurs in approximately 80% of patients.

Skeletal system findings: Patients may have mandibular hypoplasia, osteoporosis, avascular necrosis, and scoliosis.

Gastrointestinal system findings: These may include esophageal webs, hepatosplenomegaly, enteropathy, and cirrhosis.

Genitourinary system findings:: Hypospastic testes, hypospadias, and ureteral stenosis are reported.

Female carriers: Female carriers of DKC may have subtle clinical features. One study showed that 3 of 20 female carriers had clinical features that included a single dystrophic nail, a patch of hypopigmentation, or mild leukoplakia.

DKC can be characterized by cutaneous pigmentation, premature graying, of the nails, leukoplakia of the oral mucosa, continuous lacrimation due to atresia of the lacrimal ducts, often thrombocytopenia, anemia, testicular atrophy in the male carriers, and predisposition to cancer. Many of these symptoms are characteristic of geriatrics, and those carrying the more serious forms of the disease often have significantly shortened lifespans.

This disease is caused by mutation in the double stranded RNA specific adenosine deaminase (ADAR1) gene. This gene is located on the long arm of chromosome 1 (1q21).

In virology, defective interfering particles (DIPs), also known as defective interfering viruses, are spontaneously generated virus mutants in which a critical portion of the particle's genome has been lost due to defective replication. DIPs are derived from and associated with their parent virus, and particles are classed as DIPs if they are rendered non-infectious due to at least one essential gene of the virus being lost or severely damaged as a result of the defection. A DIP can usually still penetrate host cells, but requires another fully functional virus particle (the 'helper' virus) to co-infect a cell with it, in order to provide the lost factors. The existence of DIPs has been known about for decades, and they can occur within nearly every class of both DNA and RNA viruses.

Epidermolytic hyperkeratosis is a skin disorder that is present at birth. Affected babies may have very red skin (erythroderma) and severe blisters. Because newborns with this disorder are missing the protection provided by normal skin, they are at risk of becoming dehydrated and developing infections in the skin or throughout the body (sepsis).

As affected individuals get older, blistering is less frequent, erythroderma becomes less evident, and the skin becomes thick (hyperkeratotic), especially over joints, on areas of skin that come into contact with each other, or on the scalp or neck. This thickened skin is usually darker than normal. Bacteria can grow in the thick skin, often causing a distinct odor.

Epidermolytic hyperkeratosis can be categorized into two types. People with PS-type epidermolytic hyperkeratosis have thick skin on the palms of their hands and soles of their feet (palmoplantar or palm/sole hyperkeratosis) in addition to other areas of the body. People with the other type, NPS-type, do not have extensive palmoplantar hyperkeratosis but do have hyperkeratosis on other areas of the body.

Epidermolytic hyperkeratosis is part of a group of conditions called ichthyoses, which refers to the scaly skin seen in individuals with related disorders. However, in epidermolytic hyperkeratosis, the skin is thick but not scaly as in some of the other conditions in the group.

"http://ghr.nlm.nih.gov/condition/epidermolytic-hyperkeratosis"

The clinical hallmark is haemorrhagic bullae on the mucosa of the oronasopharynx. Haemorrhage from ruptured bullae, epistaxis or gastrointestinal bleeding is severe and may cause shock and death.

Onyalai is an acute disease that results in the development of hemorrhagic lesions on oral, nasal, and subconjunctival mucous membranes and skin, including on the soles of the feet. The patient initially is not in distress, which may result in a delay of diagnosis. As the disease progresses, hematuria, melena and menorrhagia may develop. Bleeding usually persists for approximately eight days, and may recur. Approximately 80 percent of cases will develop chronic thrombocytopenia. Periodic episodes of acute hemorrhage are possible and may be severe, leading to shock and death.

Epidermolytic ichthyosis (EI), (also known as "epidermolytic hyperkeratosis (EHK)", "bullous congenital ichthyosiform erythroderma (BCIE), bullous ichthyosiform erythroderma, or bullous congenital ichthyosiform erythroderma Brocq) is a rare and severe form of ichthyosis this skin disease affects around 1 in 300,000 people.

It involves the clumping of keratin filaments.

Symptoms typically are onset in the adult years, although, childhood cases have also been observed. Common symptoms include a loss of coordination which is often seen in walking, and slurred speech. ADCA primarily affects the cerebellum, as well as, the spinal cord. Some signs and symptoms are:

Exploding head syndrome (EHS), alternately termed episodic cranial sensory shock, is a benign condition in which a person hears loud "imagined" noises (such as a bomb exploding, a gunshot, or a cymbal crash) or experiences an explosive feeling when falling asleep or waking up. These noises have a sudden onset, are typically brief in duration, and are often jarring for the person. Neither the cause nor the mechanism is known. Though harmless in and of themselves, episodes have been known to create distress or impairment in the lives of individuals.

Signs and symptoms of AIED are:

- Progressive hearing loss in both ears

- Typically will begin in one ear and gradually affect the other

- Hearing loss may begin suddenly

- Tinnitus (ringing or buzzing in ears)

- Decrease in word recognition capability

- Loss of balance (vestibular symptoms)

- Degree of balance loss can change throughout the course of the disease

Exploding head syndrome is classified as a parasomnia and a sleep-related dissociative disorder by the 2005 International Classification of Sleep Disorders and is an unusual type of auditory hallucination in that it occurs in people who are not fully awake.

Several X-linked syndromes include intellectual disability as part of the presentation. These include:

- Coffin–Lowry syndrome

- MASA syndrome

- MECP2 duplication syndrome

- X-linked alpha thalassemia mental retardation syndrome

- mental retardation and microcephaly with pontine and cerebellar hypoplasia

Cadang-cadang is a disease caused by Coconut cadang-cadang viroid (CCCVd), a lethal viroid of coconut ("Cocos nucifera"), anahaw ("Saribus rotundifolius") buri ("Corypha utan"), and African oil palm ("Elaeis guineensis"). The name cadang-cadang comes from the word that means dying in Bicol. It was originally reported on San Miguel Island in the Philippines in 1927/1928. "By 1962, all but 100 of 250,000 palms on this island had died from the disease," indicating an epidemic. Every year one million coconut palms are killed by CCCVd and over 30 million coconut palms have been killed since Cadang-cadang has been discovered. CCCVd directly affects the production of copra, a raw material for coconut oil and animal feed. Total losses of about 30 million palms and annual yield losses of about 22,000 tons of copra have been attributed to Cadang-cadang disease in the Philippines.

Mesoamerican nephropathy (MeN) is a currently unexplained epidemic of chronic kidney disease of unknown origin (CKDu), prevalent in the Pacific Ocean coastal low lands of the Mesoamerican region, including southern Mexico, Guatemala, El Salvador, Nicaragua, Honduras and Costa Rica. In rural areas of Nicaragua the disease is colloquially called creatinina.

This CKD epidemic in Central America spans along a nearly 1000 kilometer stretch of the Pacific coast. In El Salvador and Nicaragua alone, the reported number of men dying from this painful disease has risen five-fold in the last 20 years, although some researchers believe hidden cases have always been there and this increment in official data could be partially due to the recent increase in reports and improved case search, pushed by the growing social and political interest in the disease. In El Salvador, the disease has become the second leading cause of death among adult men, and according to a recent editorial, it has been estimated that this largely unknown epidemic has caused the premature death of at least 20,000 men in the region. Science Magazine reports: "In El Salvador alone, PAHO's latest figures say CKD of all causes kills at least 2,500 people in the country each year".

The people affected by the epidemic are mainly young and middle-aged male laborers in the agricultural sector, particularly sugarcane workers. The disease has also been found to be prevalent in other occupations with a high risk of heat stress, implying strenuous work (miners, construction, port and transportation workers) in the high temperatures of the coastlands. The epidemic appears to affect particular Pacific coastal regions of Nicaragua, El Salvador, Costa Rica, and Guatemala.

X-linked intellectual disability (previously known as X-linked mental retardation) refers to forms of intellectual disability which are specifically associated with X-linked recessive inheritance.

As with most X-linked disorders, males are more heavily affected than females. Females with one affected X chromosome and one normal X chromosome tend to have milder symptoms.

Unlike many other types of intellectual disability, the genetics of these conditions are relatively well understood. It has been estimated there are ~200 genes involved in this syndrome; of these ~100 have been identified.

X-linked intellectual disability accounts for ~16% of all cases of intellectual disability in males.

Darier disease affects both men and women and is not contagious. The disease often starts during or later than the teenage years, typically by the third decade. Short stature is common. The symptoms of the disease are thought to be caused by an abnormality in the desmosome-keratin filament complex leading to a breakdown in cell adhesion.

Worldwide prevalence is estimated as between 1: 30,000 and 1: 100,000. Case studies have shown estimated prevalence by country to be 3.8: 100,000 in Slovenia, 1: 36,000 in north-east England, 1: 30,000 in Scotland, and 1: 100,000 in Denmark

It most commonly affects the chest, neck, back, ears, forehead, and groin, but may involve other body areas. The rash associated with Darier's disease often has a distinct odor. Palms & soles may become thickened, intra oral papules can be found. Finger nails become fragile and this helps in diagnosis of the disease. The rash can be aggravated by heat, humidity, and exposure to sunlight. In some cases, sunlight makes it better, especially in the forehead.

Minor forms of the disease are the most common, and may remain undiagnosed throughout life. These consist mainly of minor rashes without odor that are aggravated by heat, humidity, stress and sunlight. Poorly formed fingernails containing vertical striations are diagnostic.

A recent study examined neuropsychiatric conditions in a non-random sample of 100 British individuals assessed as having DAR. There were high lifetime rates for mood disorders (50%), including depression (30%), bipolar disorder (4%), suicidal thoughts (31%) and suicide attempts (13%), suggesting a possible common genetic link. Scattered case studies also suggest a possible link to learning disorders (not yet confirmed).

Onyalai is an acquired form of immune thrombocytopenia which differs clinically, epidemiologically and immunologically from idiopathic thrombocytopenic purpura.

Autosomal dominant cerebellar ataxia (ADCA) is a form of spinocerebellar ataxia inherited in an autosomal dominant manner. ADCA is a genetically inherited condition that causes deterioration of the nervous system leading to disorder and a decrease or loss of function to regions of the body.

Degeneration occurs at the cellular level and in certain subtypes results in cellular death. Cellular death or dysfunction causes a break or faulty signal in the line of communication from the central nervous system to target muscles in the body. When there is impaired communication or a lack of communication entirely, the muscles in the body do not function correctly. Muscle control complications can be observed in multiple balance, speech, and motor or movement impairment symptoms. ADCA is divided into three types and further subdivided into subtypes known as SCAs (spinocerebellar ataxias).

Recently published evidence suggest heat stress and strenuous activity-induced cyclic uricosuria and crystalluria as a possible mechanism for the tubular lesion.

Darier's disease (DAR), also known as Darier disease, Darier–White disease, Dyskeratosis follicularis and Keratosis follicularis, is an autosomal dominant disorder discovered by French dermatologist Ferdinand-Jean Darier. Darier's is characterized by dark crusty patches on the skin, sometimes containing pus. The crusty patches are also known as keratotic papules, keratosis follicularis or dyskeratosis follicularis.

Mild forms of the disease are the most common, consisting solely of skin rashes that flare up under certain conditions such as high humidity, high stress or tight-fitting clothes. Even in mild forms, short stature combined with poorly formed fingernails containing vertical striations are diagnostic.

Suudu (Tamil, pronounced ) is a culture-specific syndrome of painful urination and pelvic "heat" familiar in South India, especially in the Tamil culture. It occurs in males and females. It is popularly attributed to an increase in the "inner heat" of the body often due to dehydration. It is usually treated by the following.

1. applying a few drops of sesame oil or castor oil in the navel and the pelvic region

2. having an oil massage followed by a warm water bath

3. intake of fenugreek seeds soaked overnight in water

The problem has also been known to exist in other parts of South India and the methods of treatment are also similar.

Flacherie (literally: "flaccidness") is a disease of silkworms, caused by silkworms eating infected or contaminated mulberry leaves. Flacherie infected silkworms look weak and can die from this disease. Silkworm larvae that are about to die from Flacherie are a dark brown.

There are two kinds of flacherie: essentially, infectious (viral) flacherie and noninfectious ("bouffee") flacherie. Both are technically a lethal diarrhea.

Bouffée flacherie is caused by heat waves ("bouffée" means "sudden heat spell" in French).

Viral flacherie is ultimately caused by infection with "Bombyx mori" infectious flacherie virus (BmIFV, Iflaviridae), "Bombyx mori" densovirus (BmDNV, Parvoviridae) or "Bombyx mori" cypovirus 1 (BmCPV-1, Reoviridae). This either alone or in combination with bacterial infection destroys the gut tissue. Bacterial pathogens contributing to infectious flaccherie are "Serratia marcescens", and species of "Streptococcus" and "Staphylococcus" in the form known as thatte roga.

Louis Pasteur, who began his studies on silkworm diseases in 1865, was the first one able to recognize that mortality due to viral flacherie was caused by infection. (Priority, however, was claimed by Antoine Béchamp.) Richard Gordon described the discovery: "The French silk industry was meanwhile plummeting from a 130 million to an 8 million francs annual income, because the silkworms had all caught "pébrine," black pepper disease…He [Pasteur] went south from Paris to Alais, and rewarded them by discovering the silkworm epidemic to be inflicted by some sort of living microbe…Pasteur threw in another disease, "flâcherie," silkworm diarrhoea. The cures for both were culling the insects which showed the peppery spots — the peasants bottled the silkworm moths in brandy, for display to the experts — and rigorous hygiene of the mulberry leaf."

Symptoms of cadang-cadang develop slowly over 8 to 15 years making it difficult to diagnose at an early time. There are three main “stages” of defined series of characteristics: early, medium, and late stages. The first symptoms in the early stage develop within two to four years of infection. These symptoms include scarification of the coconuts which also become rounded. The leaves (fronds) display bright yellow spots. About two years later, during the medium stage, the inflorescences become stunted and eventually killed, so no more coconuts are produced. Yellow spots are larger and in greater abundance to give the appearance of chlorosis. During the final stage, roughly 6 years after the first symptoms are recorded, the yellow/bronze fronds start to decrease in size and number. Finally, all the leaves coalesce, leaving just the trunk of the palm “standing like a telephone pole”.

Palms under 10 years of age are rarely affected by cadang-cadang; the incidence of disease increases until about 40 years of age and then plateaus. "No recovery has ever been observed, and the disease is always fatal". African oil palm has similar symptoms as coconut but also have orange spotting on palms.

Heat illness or heat-related illness is a spectrum of disorders due to environmental exposure to heat. It includes minor conditions such as heat cramps, heat syncope, and heat exhaustion as well as the more severe condition known as heat stroke.