A 37-year-old man presents with a complaint of a scalp rash that first appeared several months ago. On his friends’ advice, he tried changing shampoos and applying tea tree oil, with no discernible improvement. He has never had problems with his scalp before, but there is a family history of “unknown skin disease” (mentioned by his father in past conversations). The patient denies any other skin problems.

Recently, he’s experienced a lot of stress: job loss, marital strife, and a subsequent increase in alcohol intake. He has also gained weight, adding that he isn’t getting any exercise. He denies joint pain or swelling.

EXAMINATION
Faint scaling is seen in the patient’s scalp, most of it over and behind the ears. These areas are modestly excoriated as well. There is similar faint scale in both external auditory meati. Examination of the fingernails reveals modest, scattered pits in four nail plates, which the patient says have been there “on and off for years.”

Looking elsewhere, focal heavy white scaling is noted on one knee and both elbows. These findings prompt examination of the patient’s upper intergluteal area, where definite pinkish erythema is observed. It covers an area of 7 x 4 cm, with no significant scaling.

DISCUSSION
You might expect a skin disease that “runs in the family” to be well known to all of them, but in truth, it’s quite common for family members to suffer for years without seeking evaluation by dermatology. Even worse, they might be misdiagnosed by someone else and spend a lifetime thinking they have “eczema” or “ringworm,” and passing this misinformation on to their kin.

Psoriasis is like that; it can present in so many ways, and it can also vary extensively in severity and morphology from one generation to another. As such, while most cases of psoriasis are obvious and therefore easy to diagnose, some are more obscure.

It helps to know how common psoriasis is: It affects 3% of the population, which equates to about 9 million people in the United States. Many, like this patient, have relatively mild cases that flare with stress. Known stressors include infection (especially strep) or introduction of certain medications (eg, β-blockers and lithium). A history of genetic predisposition can be obtained in about 30% of such cases.

This case illustrates a major point about the diagnosis of psoriasis: Often, it must be cobbled together from a collection of findings that appear disconnected on first glance. The scalp findings, by themselves, could have simply represented dry skin or seborrhea. However, taken in context with the nail changes, the family history, the extensor involvement, and intergluteal “pinking,” an almost certain diagnosis emerges.

The intergluteal pinking, by the way, can also be seen with seborrhea—so it’s not pathognomic for psoriasis but is highly suggestive of that diagnosis. The salmon-pink color and lack of scaling (because of the friction and moisture in the affected area) are especially typical.

Those tempted to dismiss all of this as mere sophistry have likely never experienced the effects of this disease, which is notorious for its association with serious negative psychologic repercussions, such as depression, isolation, and suicide. Imagine, for example, having to vacuum out your bed and surrounding carpet every morning just to remove the skin that was shed overnight, then having to be seen and judged by the public.

And that’s not even the worst of it. Up to 30% of psoriatic patients go on to develop psoriatic arthropathy, a destructive form of inflammatory arthritis that is relentless in its course without correct diagnosis and treatment. We know a great deal more about this autoimmune disease now than when I started out in dermatology, and we have marvelous treatment for it, more of which are in the research pipeline.

But these are of little use without the one essential ingredient the clinician must supply: a correct diagnosis.

TAKE-HOME LEARNING POINTS
• Weight gain, smoking, and stress are all documented triggers for psoriasis.

• A positive family history of psoriasis can be obtained in about 30% of suspected cases, but a negative history does not rule out the diagnosis.

• Certain medications, such as β-blockers and lithium, can trigger exacerbations of psoriasis.

• Psoriasis often presents with what appear to be unrelated findings, such as scalp rash, nail pits, genital involvement, and intergluteal pinking.

• Psoriasis is associated with significant psychologic pathology, including poor body image, depression, isolation, increased incidence of drug and alcohol abuse, and suicide.

• Almost 30% of psoriasis patients will develop a related form of arthritis called psoriatic arthropathy.

• Effective treatment is available for psoriasis and psoriatic arthropathy, but these conditions must first be suspected and diagnosed.

A Little Pink in the Cheeks Signals Serious Problem