DISCUSSION
This is a typical case of guttate psoriasis, which is genetic in predisposition but triggered by strep in the susceptible patient. It’s tempting to partially attribute this case to the child’s high stress level, but this is purely speculative.
Psoriasis affects about 7 million people in the US—more than 150 million worldwide—in a variety of forms. The guttate morphology is seen primarily in children, with plaques that favor extensor surfaces of the arms, trunk, and legs. Biopsy was not needed in this case; if performed, it would have shown characteristic changes (eg, parakeratosis, fusing of rete ridges).
These changes occur because psoriasis, an autoimmune disease, targets keratinocytes—cells that regenerate over a 28-day period to replace the outer layer of skin as it flakes off. With psoriasis, this process is accelerated; keratinocytes move and slough off within a week, creating scaly, inflamed lesions.
Long-term follow-up is needed to monitor the patient’s overall health, because psoriasis increases comorbidity of conditions such as coronary vessel disease, diabetes, stroke, and cancer. In patients with any form of psoriasis, there is the potential for psoriatic arthropathy, a destructive, crippling form of arthropathy that affects up to 25% of all patients. And in a third of guttate psoriasis cases, the condition evolves into permanent plaque psoriasis. For this reason, the guttate variety must be treated aggressively with a combination of phototherapy and topical steroids, adequate treatment of any residual strep, and, in adults, the occasional addition of methotrexate.
Regarding the family’s concern, measles does not involve scaly papules and plaques and would likely cause other constitutional symptoms (eg, fever, malaise, myalgia). The other item in the differential, tinea corporis, involves lesions that are not as uniformly scaly, numerous, or evenly spaced. And with tinea, scaling typically occurs on the peripheral leading edge of the lesion.
TAKE-HOME LEARNING POINTS
- Guttate psoriasis is more common in children than in adults and is often triggered by strep infection, though stress has also been implicated as a trigger.
- In about a third of all cases, this type evolves into permanent plaque psoriasis. All patients with psoriasis are at risk for psoriatic arthropathy (25% of patients).
- Measles does not involve scaly papules and plaques and would likely cause constitutional symptoms (eg, fever, malaise, myalgia).
- Tinea corporis lesions are not uniformly scaly, nor would they be as numerous or evenly spaced; most of the scale in tinea is seen on the peripheral leading edge of the lesion.