Tuesday, July 10

Acute urticaria (hives)

Home > Chronic hives > Acute urticaria

What is acute urticaria?

Acute urticaria (AU) are distinct skin conditions characterized by itchy welt or wheals appearing as flat-topped, round, annular or geographic pale-pink-red papules or plaques typically evanescent, resolving and disappearing within 24 to 48 hours.
In rare cases the AU manifestations last longer. If the weal lasts longer than six weeks it is classified as chronic urticaria (CU). It is found that 20% to 30% of the cases of acute weals recur and some evolve into chronic cases. Au is one of the common medical condition known and its life time prevalence is 10% -25%.

The weals/papules can suddenly appear on any area of skin. Adjoining papules may join together to form larger swollen areas known as plaques. The weals may fade gradually and the skin may become normal in a short time. As some papules fade some fresh papules may also appear. The associated itching and the blotched appearance of the affected skin is very distressing.

In some cases AU is associated with angioedema. Angioedema often causes swelling of eyelids, lips and sometimes tongue. The puffiness may also occur in the face, ears, hands, feet and genitalia. Usually the swellings do not cause itching and are painful. The swelling occurs in the deeper layers of skin. Along with cutaneous manifestations of acute weals some people get extra cutaneous manifestations such as body ache, joint pains and gastrointestinal tract problems. This is probably due to systemic effect of inflammatory mediators released by mast cells present in the skin as well as by the local mast cells.

Causes of acute urticaria

The basic cause of all types of urticaria is activation of cutaneous mast cells and release of histamine and other mediating chemicals of inflammation. Histamine by activating the endothelium and dilating capillary venules causes blood plasma to leak into the interstitial spaces. This causes edema, reddening, warmth, itching and pain.

Possible triggers of Acute urticaria

In children dominating causative factors are viral infections, medication intolerance and food allergies. In adults also acute infections, food allergies and chemical allergies play a triggering part. Other triggers include insect stings, exposure to cold, exposure to sun, contact with chemicals, inhalation of allergens, fish, shellfish, nuts, egg, cow's milk etc.  In half of all the cases, acute urticaria are idiopathic, appearing spontaneously without any known provocation.

Treatment for acute urticaria

As acute urticaria is self-limiting it is treated symptomatically to completely suppress the clinical manifestations. Taking antihistamines eases itching and the condition resolves after some time. Treatment regimen include glucocorticoids or non-sedating antihistamines alone or in combination depending upon the requirement.

Risks involved in acute urticaria

Anaphylaxis causes difficulty in breathing and asphyxiation. When AU is associated with anaphylaxis, it is life-threatening and is a medical emergency. Anaphylaxis is rapid in onset and may cause death. The first-line therapy for anaphylaxis is immediate intramuscular administration of epinephrine and hospitalization for further treatments until recovery.
Related topics of interest:
Chronic urticaria treatment
Types of urticaria
References:
1.Marcus Maurer and Jürgen Grabbe, Urticaria: Its History-Based Diagnosis and Etiologically Oriented Treatment, Dtsch Arztebl Int. 2008 June; 105(25): 458–466. PMCID: PMC2696901
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Saturday, July 7

Albinism causes - Albinism disorder types and genetics

Home > White skin discoloration > Albinism facts > Albinism disorder causes, types and genetics
There are several types of albinism disorders and all types are caused by genetic defects rendering the body incapable of producing or distributing melanin pigment.
Most of these genetic defects are caused by recessive alleles. A person has to receive the defective genetic material from both the parents to get the albinism disorder. If the person receives the mutated gene from only one parent, he will be normal, but will be a genetic carrier. Normally carrier-parents have 25% chances for producing children with albinism disorder. There are currently 15 genetic locations in the chromosomes that have been associated with albinism.

Genetic defects affecting melanin pathway causes albinism disorders

The pigment melanin is formed in the melanocytes present in the skin, hair follicles and pigment cells of the eye. The production of melanin involves a series of enzymatic reactions converting the amino acid tyrosine into two types of melanin, namely black-brown eumelanin and red-blond pheomelanin. Genetic mutations affecting proteins and enzymes involved in melanin production pathway cause  non-production or reduced production of melanin. Tyrosinase enzyme has a major role in converting tyrosine to DOPA. DOPA is then converted to dopaquinone and then to eumelanin or pheomelanin. Tyrosinase-related protein 1 and tyrosinase-related protein 2 are also involved in formation of eumelanin. P protein (a melanosomal membrane protein) is involved in the transport of tyrosine for mealnin synthesis. Any genetic mutation affecting these enzymes and proteins can cause albinism disorder.

Genetics and causes of oculocutaneous albinism (OCA)

In oculocutaneous type of albinism disorder eyes (ocular), skin (cutaneous) and hair are involved. One of the four mutated genes causes this albinism disorder. Oculocutaneous albinism has four sub types OCA1, OCA2, OCA3 and OCA4 caused by mutated genes TYR, OCA2, TYRP1, and SLC45A2 respectively.
 
Oculocutaneous albinism type 1 (OCA1) is Tyrosinase-Related OCA and is caused by mutated TYR gene on the chromosome 11. There is a genetic defect in the tyrosinase enzyme which is responsible for the metabolism of amino acid tyrosine into Melanin pigment. Oculocutaneous albinism type 1 is transmitted by autosomal recessive inheritance. The characteristics of OCA1 type are deficient melanin synthesis in the skin, hair and eyes, nystagmus, reduced visual acuity and iris translucency.  At birth the affected children with this type of albinism disorder usually have white skin, white hair and blue eyes. Later on some of them may produce some pigment to have a slight tan and blond hair.

Oculocutaneous albinism 1A (OCA1A) is Tyrosinase-Negative OCA. The genetic defect in the tyrosinase enzyme makes it inactive and melanin is not produced. Individuals having oculocutaneous albinism type 1A have white hair and skin. The skin does not tan and the iris remain translucent and does not darken with age. It causes reduced visual acuity.

Oculocutaneous albinism 1B (OCA1B) is Yellow OCA. The genetic defect in the tyrosinase enzyme makes it minimally active and a small amount of melanin pigment is produced. Individuals with oculocutaneous albinism type 1B have white or light yellow hair and white skin at birth. The hair may darken with age. The skin may develop light pigment and tan. The blue iris at birth may turn hazel/green/brown with age. Individuals having OCA1B type disorder have better visual acuity when compared to OCA1A type individuals.

Temperature-sensitive albinism is a sub-type of oculocutaneous albinism type 1B. In this genetic disorder there is mutation in tyrosinase gene and causes temperature-sensitive tyrosinase enzyme to be produced. Temperature-sensitive tyrosinase enzyme has reduced activity than normal tyrosinase enzyme at normal temperatures (37*C). Its activity improves with lower temperatures. Parts of the body with normal temperature like scalp hair and axillary hair have minimal pigment while cooler areas of the body like arms and legs are greatly pigmented.

Oculocutaneous albinism type 2 (OCA2) is caused by OCA2 gene mutation on the chromosome 15. In OCA TYpe 2 disorder there is a genetic defect in P protein which helps in the function of tyrosinase enzyme. Oculocutaneous albinism type 2 disorder is transmitted by autosomal recessive inheritance. OCA2 is characterized by reduced pigmentation of the skin, hair and iris. This type of disorder causes ocular defects, including nystagmus, iris translucency and reduced visual acuity. Skin pigmentation may vary from minimal to near-normal. Newborns have pigmented hair ranging from very light yellow to brown. There is a variant of OCA2 disorder identified in Africans and African Americans which causes light brown skin and hair.

Oculocutaneous albinism type 3 (OCA3) is caused by mutation of TyRP1 gene on the chromosome 9. OCA type 3 disorder is transmitted by autosomal recessive inheritance. This is a very rare type of disorder caused by genetic defect in TYRP1, a protein related to tyrosinase enzyme. There is substantial pigmentation in people with OCA3.

Oculocutaneous albinism type 4 (OCA4) is caused by mutated SLC45A2 gene on the chromosome 5. This disorder is caused by defect in the SLC45A2 protein that helps the function of tyrosinase enzyme. OCA4 is transmitted by autosomal recessive inheritance. OCA4 is characterized by reduced pigmentation of the skin, hair and iris. Ocular defects include nystagmus, iris translucency and reduced visual acuity. Skin pigmentation may vary from minimal to near-normal. Newborns have some pigmentation in hair ranging from silvery white to light yellow. OCA4 is rarer except in people of Japanese origin.

Genetic causes of ocular albinism

Ocular albinism (OA1) is caused by mutation of GPR143 gene on X chromosome. It is passed on to sons by carrier-mother (50% chances). For the daughters to inherit OA1, father must have OA1 and mother should be either a OA1 (100% chances) or carrier (50% chances). Ocular albinism disorder affects only eyes and causes minimal pigment in them. Reduced visual acuity, nystagmus, and difficulty controlling eye movements are caused in persons with ocular albinism.

Hermansky-Pudlak Syndrome (HPS)
HPS is a rare type of albinism and is autosomal recessive. This disorder is more common in Puerto Rico.
HPS can be caused by mutations in several genes: HPS1, HPS3, HPS4, HPS5, HPS6 and HPS7. HPS shows all the characteristics of oculocutaneous albinism. HPS also has bleeding problems due to a platelet abnormality in lacking dense bodies and storage of an abnormal fat-protein compound. This disorder may also involve lung and bowl malfunctions.

Chediak-Higashi Syndrome (CHS)
CHS is a rare autosomal recessive disorder caused by the mutation of LYST gene. Individuals with CHS show characteristics of oculocutaneous albinism, having light skin and silvery hair. They are also afflicted by solar sensitivity, photophobia, frequent infections and neuropathy. A defect in the granules present in skin pigment cells and white blood cells causes this type of albinism associated with immunodeficiency. Albinism disorder is typically partial, and some individuals may also have peripheral neuropathy.

Griscelli Syndrome
Griscelli syndrome is a rare autosomal recessive disorder, characterized by albinism with immunodeficiency and neurological problems. It usually causes death in early childhood.

To sum up there are various genetic causes giving rise to various types of albinism disorders requiring further research and social efforts to alleviate the problems of the affected people.
Topic of interest:
Causes of chronic hives
References:
Richard A King, MD, PhD, FACMG and William S Oetting, PhD., Oculocutaneous Albinism Type 2, University of Minnesota Health Center, Minneapolis, PMID: 20301410.
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Thursday, July 5

Facts and information about albinism disorder

Home > White skin discoloration > Facts and information about albinism disorder
Albinism disorder in fact is not a disease and albinos have an inherited condition in which little or no pigment is produced by the body, affecting the color of their skin, eyes and hair.
In albinism, the genetic information and gene expression are altered and the required amount of melanin pigment is not produced, sometimes with debilitating health and vision issues. In fact, the prevalence of this genetic disorder is approximately one individual for every seventeen thousand individuals.

Albinism affects individuals of all racial and ethnic backgrounds. Except for ocular type all other types affect both men and women equally. In fact most of the children with albinism have normal parents. Albinism is caused by inheriting recessive genes from both the parents in oculocutaneous type and from mother in ocular type.
Image - Horizontal nystagmus
Albinism vision problems

Facts about types of albinism

As albinism may involve different genes, there are different types.
In oculocutaneous albinism (OCA) pigmentation of the skin, hair and eyes is affected. There are subtypes like OCA1, OCA2, OCA3, and OCA4. The pigmentation ranges from near lack of it to slight amount of pigmentation.
Ocular albinism (OA) is a rare type wherein only the pigment in the eyes is affected. In fact the affected person has skin and hair coloration similar or slightly lighter than that of his ethinicity. This type is linked to X-chromosome affecting only boys and is passed on from mother to son.
Hermansky–Pudlak syndrome (HPS) is a rare autosomal recessive disorder which results in oculocutaneous albinism and bleeding problems due to a platelet abnormality.
Griscelli syndrome is a rare autosomal recessive disorder characterized by hypopigmentation with immunodeficiency.
Chédiak–Higashi syndrome is a rare autosomal recessive disorder which results in recurrent infections, partial albinism and peripheral neuropathy.

Facts about vision issues

Depending upon the form, albinos have various degrees of vision impairment. Some affected persons may be nearly blind whereas some may be able to even drive a vehicle.
There are varying degrees of impairment in the development of retina of the affected persons. Further there is impairment in the nerve connection between eye and brain.
Some of the vision problems of affected people are astigmatism (blurred vision), photophobia (eye sensitivity to light and glare), near-sightedness, far-sightedness, nystagmus and crossed eyes.

Facts about health issues

But for vision problems, affected persons lead a normal life and have an average life span. Persons with oculocutaneous type have very little pigment on the skin and can suffer sunburns easily. Proper sun protection in the form sunscreen creams, hats and clothing is necessary. They are also easily affected by UV sunlight and are prone to skin cancer as they lack protective melanin pigment. Persons affected by Hermansky-Pudlak, Griscelli Syndrome or Chediak-Higashi syndrome have other health issues like bleeding, neuropathy and immunodeficiency and their life stye and life span may be severely affected.

Facts about social issues

In many regions of the world, people mistake the skin coloration of albinos for a contagious infection and stigmatize the affected people. Even their paternity and ethinicity are questioned. It is very necessary to educate their neighbors and school-mates about the facts of albinism to overcome stimatization. In fact in some parts of Africa violence is perpetuated on albinos based on witchcraft tales, beliefs and cures.
Topic of interest:
Albinism types and their genetic causes

Image credit: http://en.wikipedia.org/wiki/User:Student_BSMU/ (CC BY-SA 3.0)
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