Summary

SICKLE CELL

Sickle-cell disease occurs more commonly in people (or their descendants) from parts of the world such as sub-Saharan Africa, where malaria is or was common, but it also occurs in people of other ethnicities.

Most sickle cell disease patients have no painful crises.

This is because those with one or two alleles of the sickle cell disease are resistant to malaria since the red blood cells are not conducive to the parasites – in areas where malaria is common there is a survival value in carrying the sickle cell genes.

One long-held theory as to why it was so common in the tropics was its association with malaria. In the 1940s, E.A.Beet, a British medical officer stationed in Northern Rhodesia (now Zimbabwe), observed that blood from malaria patients who had sickle cell trait had fewer malarial parasites than blood from patients without the trait.

Following this observation, a physician in Zaire reported that there were fewer cases of severe malaria among people with sickle cell trait than among those without it.

In 1954, Anthony Allison, continued to build on these observations and hypothesized that sickle cell trait offered protection against malaria. He suggested that those with the trait did not succumb to malaria as often as those without it; but, when they did, their disease was less severe. It is now known that, when invaded by the malarial parasite, normally stable red cells of someone with the sickle cell trait can sickle in a low oxygen environment (like the veins).

The sickling process destroys the invading organism and prevents it from spreading through the body. This apparent ability of a genetic condition to protect carriers is particularly important in infants. Thus, in regions repeatedly devastated by malaria, people who carry the sickle cell trait will have a greater chance for survival than other individuals.

There are several theories as to why people with sickle cell trait have milder cases of malaria. This has to do with their being a host to fewer and weaker parasites:

MELANOMA

Melanoma is the most dangerous type of skin cancer. It often starts out as a coloured mole or spot, but can spread fast to surrounding skin and other organs. Melanomas make up only one or two per cent of all skin cancers, but is the type most likely to be fatal.

What causes melanomas?

The biggest contributing factor is the skin’s sensitivity to ultraviolet (UV) rays. Melanoma cancer typically starts in areas exposed only occasionally to the sun, such as the back, and the backs of the legs. Who’s at risk?

People who have:

• * Lots of moles, particularly atypical moles (irregular shaped, but benign).
• * Family history of melanoma in more than one relative.
• * Blond or red hair.
• * Fair or freckled complexion.
• * Had a severe sunburn during childhood.As well, incidence rates and mortality rates appear to be higher for men.
  

  Are rates rising?

  Yes, says Dr. Gang Li, associate professor of dermatology and skin science at the University of British Columbia.

  “It’s increased quite dramatically in the past few decades,” says Li. He says it’s unclear why, but he has a couple of theories.

  “One thing could be the thinning of the ozone layer, which provides a filter for the UV light,” he says. “If the ozone becomes thin, there is more UV light. Another thing is a lot of people like going to the beach and getting a suntan.”

  Melanoma incidence rates are increasing for both men and women.

• Dysplastic nevi, which are more likely than ordinary moles to become cancerous. Dysplastic nevi are common, and many people have a few of these abnormal moles. The risk of melanoma is greatest for people who have a large number of dysplastic nevi. The risk is especially high for people with a family history of both dysplastic nevi and melanoma.
• Many (more than 50) normal moles: Having many moles increases the risk of developing melanoma.
• Fair skin: Melanoma occurs more frequently in people who have fair skin that burns or freckles easily than in people with dark skin. Those at risk usually have red or blond hair and blue eyes.
• Personal history of melanoma or skin cancer: People who have been treated for melanoma, basal cell carcinoma or squamous cell carcinoma are at increased risk of getting melanoma.
• Family history of melanoma: Melanoma can be hereditary. Having two or more close relatives who have had this disease is a risk factor. About 10 percent of all patients with melanoma have a family member with this disease.
• Weakened immune system: People whose immune system is weakened by certain cancers, HIV or drugs given following organ transplantation are at increased risk of developing melanoma.
• Severe, blistering sunburns: People who have had at least one severe, blistering sunburn as a child or teenager are at increased risk of melanoma. Sunburns in adulthood are also a risk factor for melanoma.
• Ultraviolet (UV) radiation: Experts believe that much of the worldwide increase in melanoma is related to an increase in the amount of time people spend in the sun. UV radiation from the sun causes premature aging of the skin and skin damage that can lead to melanoma. Artificial sources of UV radiation, such as sunlamps and tanning beds, also can cause skin damage and increase the risk of melanoma. While research has shown these are risk factors, many people who do get melanoma have no known risk factors.

Melanoma Signs and Symptoms

Be alert to any kind of change in a mole. The four most common and most significant signs of change are a mole or skin area that:

• Changes in size
• Changes in color—typically gets lighter and/or darker
• Itches
• Bleeds

Most melanomas have a black or blue-black area. Melanoma also may appear as a new mole. It may be black, abnormal or “ugly.”

Melanomas can arise in a mole that has been present for your entire life, or can start in as a new mole or dark pigmented area on the skin.

In more advanced melanoma, the texture of the mole may change. For example, it may become hard or swollen.

Melanomas may feel different from regular moles. More advanced tumors may itch, ooze or bleed. However, melanomas usually do not cause pain.

Remembering your “ABCDEs” can help you remember what to watch for:

• Aysmmetry — The shape of one half does not match the other.
• Border-The edges are often jagged, uneven, distorted or atypical in outline; the pigment may spread into the surrounding skin.
• Color-The color is uneven. Shades of black, brown, and tan may be present. Areas of white, gray, red, pink or blue also may be seen.
• Diameter-There is a change in size, usually an increase. Melanomas are usually larger than the eraser of a pencil (1/4 inch or 5 millimeters).
• Evolution-anything that changes over time.

Melanomas can vary greatly in how they look. Be aware of any mole or abnormality of the skin that does not heal over time.

We see more and more patients with melanomas that present in atypical ways.

Often, patients report a red, raised area that looked like a “pimple” or “cyst” that just does not heal over time and gets worse. Although this is not the typical presentation of melanoma, this certainly can happen.