The Itch in humanity

DR. PRASAD Kumarasinghe (Dermatologist, Colombo North Teaching Hospital) writing on Pruritus (itching) in the March issue of Sri Lanka Prescriber says, "Pruritus (itching) is the commonest symptom in Dermatology, which has a variety of diverse causes, and it would be correct to say that all humans itch often in their lives."

A copy of the Prescriber issue with this article has been sent to the HealthWatch for use by Prof. Colvin Goonaratne, one of the editors of the publication which is being put-out by the Department of Pharmacology of the Colombo Medical Faculty.

We wish to thank Prof. Goonaratne and the Pharmacology Department of the Colombo Medical Faculty for giving us the right to use the article and the other material in the publication on this page.

Pruritus could lead to depression

PRURITUS is the commonest symptom in dermatology. It has a variety of diverse causes. It would be correct to say that all humans itch often in their lives.

Often pruritus is a troublesome symptom of a common benign disease, but it may be the presenting symptom of a life threatening condition such as an internal malignancy.

Chronic intractable pruritus could even lead to depression. Careful evaluation of patients with pruritus, especially in cases of generalised pruritus, is essential.

Types of pruritus

Pruritoceptive - pruritus originating in the skin from inflammation, dryness or other skin injury eg. eczema, insect bites, scabies.

Neuropathic - pruritus due to pathology originating from any point along the afferent pathway eg. postherpetic neuralgic itch, brachioradial pruritus.

Neurogenic - pruritus originating centrally, but without evidence of neural pathology eg. itch of cholestasis from the action of opioid neuropeptides on opioid receptors.

Psychogenic - pruritus associated with psychologic abnormalities eg. delusional parasitosis.

Pruritus in dermatology can be subdivided into localised (eg. contact dermatitis) and generalised (eg. erythroderma) forms. Clinical presentation and other associated features vary depending on the cause of pruritus. Lichenification and hyperkeratosis are features of chronic scratching.

Causes of generalised pruritus
Extensive dermatitis
Xerosis
Urticaria
Miliaria (sweat rash)
Drug induced pruritus
Exfoliative dermatitis - eczema, psoriasis, pityriasis rubra pilaris, mycosis fungoides
Parasitic eg. scabies, filariasis
Insect bites
Irritating clothes eg. wool
Pityriasis rosea
Lichen planus
Psoriasis
Renal causes eg. chronic renal failure
Hepatic eg. cholestatic jaundice,
primary biliary cirrhosis, cholestasis of pregnancy
Haemopietic eg. polycythemia, iron deficiency anaemia, myeloma, mastocytosis, Hodgkin and non Hodgkin lymphoma
Endocrine eg. hyperthyroidism, carcinoid syndrome, anorexia nervosa
Delusional parasitosis
Nodular prurigo
Lichen amyloidosis
Connective tissue disorders
eg. dermatomyositis, Sjogren syndrome
Infections eg. varicella zoster, HIV
Malignancy

The itch-scratch-itch cycle

In general, management of pruritus depends on many aspects including cause of itch, intensity of itch, psychological and mental status, other associated abnormalities including liver pathology, known hypersensitivities to drugs, age of the patient, in women, whether pregnant or not, etc.

Whenever possible the cause of pruritus should be treated or eliminated. Several investigations may become necessary if the cause of pruritus is not obvious after a careful history and examination. Identifying aggravating and relieving factors are also important.

Itch threshold is lower in the elderly compared to younger patients. The itch-scratch-itch cycle seems to propagate pruritus and its sequelae. A flexible approach with appropriate patient education, and topical and systemic medication may be needed to alleviate itch.

Systemic treatment

Antihistamines - Oral antihistamines are the most commonly used systemic antipruritics. Sedating antihistamines (eg. promethazine, chlopheniramine) appear to be more effective than non-sedating antihistamines.

Hydroxyzine is particularly useful for nocturnal itch. Although newer antihistamines (eg. desloratadine, fexofenadine) are more effective in histamine induced pruritus (eg. urticaria, insect bites) they are not very effective in pruritus due to other causes.

If pruritus is severe, a sedating antihistamine for the night and a non-sedating newer antihistamine for daytime may be used. When antihistamines are prescribed patients should be warned of possible sedation and about driving and operating machines.

Certain antihistamines may cause cardiac arrhythmias eg. terfenadine. In pregnancy, as far as possible, it would be prudent to use only the time tested antihistamines such as chlorpheniramine maleate.

Treatment of neuropathic itch

There is no consistently effective treatment for this type of itch. Capsaicin and topical anaesthetics have been reported to be useful.

Treatment of neurogenic pruritus

Therapeutic options for neurogenic itch are based on the antagonistic action between itch and pain at the spinal level. Opioid antagonists eg. naloxone and nalmefene have been used effectively in cholestatic pruritus.

Treatment of psychogenic itch

Antidepressants such as selective serotonin reuptake inhibitors, and tricyclic compounds such as doxepin, appear to be beneficial in this type of itch. Newer drugs include sertraline and mirtazapine.

Treatment depends on the cause

In summary, treatment of pruritus depends on the cause and other patient related factors. Where the cause of itch cannot be eliminated or controlled, there is no consistently effective treatment for the symptom of itch.

Treatment should be according to the type and cause of itch. Combined measures eg. counselling, topimentary in treating itch.

Meningitis - How to be safe
 

BY PROF. NADARAJA Bathithunathan

MENINGITIS is inflammation of the meninges the membranes covering the brain. It is more common than other affections of the brain, encephalitis and brain abscesses. Damage to the brian is a serious condition. In fact the modern definition of death is 'irreversible brain damage!'

Microbial infection

The inflammation is caused by microbial infection. We live in a sea of microbes, mainly bacteria, fungal spares and viruses all around us. Our body is covered with bacteria about 10 cm.

They are also found in the same concentration in the mouth, throat, intestines and genitals.

These are mainly protective friendly bacteria (commensals) which keep disease producing organisms at bay. These commensals are part of our innate immune system which protect us continuously so long as we are alive.

The innate immune system

The innate immune system had evolved over 600 million years. When animals first appeared on earth during the precambrian era the biggest threat they faced was infection by microbes which had inhabited the earth for 2 1/2 billion years before them.

Survival depended on the development of powerful defence mechanisms against these microbes which found the animal tissues an excellent medium in which to live comfortably and multiply as parasites.

When Microbat infect

When microbes infect an animal tissue the innate immune system comes into play immediately and sets up inflammation.

Doctors use the suffix -ibis to describe this condition e.g. tonsillitis (inflammation of the tonsil) sinusitis, conjunctivitis, gastritis, enteritis, cystitis, urethritis, vaginitis etc. The diagram shows briefly the innate immune mechanisms causing inflammation.

Our brain is well-protected

Our brain is very well protected, much better than for example the bladder or the throat. Meningitis is a rare condition. Encephalitis (inflammation of the brain) and brain abscesses are even more rare.

Meningitis occurs only when the immune system is immature as in very young children or the defence mechanisms have been weakened due to other diseases (e.g. cancer, AIDs etc., malnutrition, chronic stress, old age and in some inherited conditions of immune deficiency).

Protective mechanisms

However the protective mechanisms are matched by the virulence of the infecting organisms and the mode of transmission.

For example during epidemics of meningococcal meningitis, the meningococcus which has a special affinity, for the meninges (like the gonococcus for the urethra) increases in virulence and causes meningitis in healthy adults and adolescents.

Intrathecal injection

Doctors sometimes inject medicines directly into the Cerebrospinal Fluid (CSF) for therapeutic purposes. This is called an intrathecal injection. If they use contaminated syringes the organisms get directly into the CSF and cause meningitis.

This is what is acknowledged to have happened in the recent meningitis epidemic in the Colombo maternity hospitals. Drug addicts who use contaminated syringes to inject themselves may introduce the microbes directly into the body with a weakened immune system and get meningitis.

When microbes are directly introduced into CSF

There has been an explosion in our understanding of innate immunity during the past 10 years. I shall use one aspect of it to explain what happens when microbes are directly introduced into the CSF.

The phagocytic white blood cells, neutrophils, come out immediately to attack the invading organism. Normally these amoeba like cells crawl on solid surfaces, gabble up and kill the microbes by a variety of killing methods.

However when this happens in the CSF, the neutrophils cannot home in on the microbes in the liquid medium. But they are activated and the frustrated neutrophils degramulate and flutter around releasing their lysosomal contents, free radicals hypochlorous acid and other substances which damage the brain.

Any parenteral injection should be sterile. But extreme care should be taken (to prevent organisms getting into the CSF) when making intrathecal injections. In fact intrathecal injections should be avoided as far as possible.

Protecting from infections

How can we protect ourselves from infections? It is quite simple. Healthy living develops a powerful immune system: plenty of pure water, fruits and vegetables, fresh air, clean satisfying physical and mental activity, the warmth of human love, care, kindness and compassion.

It is also important to recognise symptoms of meningitis especially in young children and get prompt treatment. Any abnormal behaviour suddenly appearing with fever, severe headache, viridity of the neck, slurred speech clouding of consciousness, nausea and vomiting calls for immediate attention. Prompt treatment with modern antibiotics can be quite effective.

(The writer is a visiting Professor of Transfusion Medicine MGR University, India)

Air pollution tied to increased risk of strokes

NEW YORK - Increases in particles polluting the air are associated with an increase in the number of strokes caused by a blood clot in the brain - but not the type caused by an artery rupture in the brain - new research shows.

Previous reports have shown a link between air pollution and overall risk of heart attacks and other cardiovascular events, but the specific effect on stroke risk has not been well studied, lead author Dr. Gregory A. Wellenius, from Beth Israel Deaconess Medical Center in Boston, told Reuters Health. "Our study is the first large study in the US to address this topic," he said.

The researchers evaluated the link between air pollution and stroke among Medicare recipients in nine US cities.

Specifically, they analyzed data on 155,503 artery-blockage (ischemic) strokes and 19,314 bleeding (hemorrhagic) strokes recorded as hospital admissions between 1986 and 1999.

As reported in the American Heart Association's journal Stroke, the team found that an increase in particulate air pollution from the lowest to the highest levels raised ischemic stroke admissions by 1.03 percent on the same day.

Further analysis yielded similar results for levels of carbon monoxide, nitrogen dioxide, and sulfur dioxide. By contrast, the investigators found no association between air pollution and hospital admission for hemorrhagic stroke.

Wellenius cited three possible mechanisms, which alone or in combination might explain how air pollution promotes stroke.

"One possibility is through inflammatory effects. The other is through pulmonary reflexes that trigger changes in blood pressure or heart rate." A third possibility is changes in clotting factors that tend to promote more blood clots.

Although the increase in ischemic stroke risk is small, the number of excess strokes can be high because pollution affects the whole population.

"Taken together with previous reports, the results suggest that reducing exposure to air pollution is likely to reduce the risk of a number of health problems, including heart disease and stroke," Wellenius concluded.

SOURCE: Stroke, December 2005. REUTERS