Psoriasis is an inflammatory skin condition that shows up in several forms. The two that appear most in children are:

• Plaque psoriasis. This is the most common type. If your baby has a raised, red lesion covered with a flaky, silvery-white scale, he may have it. Plaque can show up anywhere, although it most often appears on the elbows, knees, scalp, and lower back.

• Guttate psoriasis. This type of psoriasis is more common in children than in adults. It isn't as scaly or thick as plaque. Instead it appears as small, dot-like lesions, usually on the trunk and limbs.

There are mild cases of psoriasis, with only a few lesions; moderate cases, in which 3 to 10 percent of the body is covered; and severe cases, in which more than 10 percent — and sometimes the whole body — is covered.

Psoriasis isn't very common in babies. More likely possibilities at this age include a bad case of seborrheic dermatitisor cradle cap (if it's on your baby's scalp) or a bad diaper rash, if it's in his genital area.

Ringworm can also produce red skin with a flaky scale. Eczema, which can be difficult to distinguish from psoriasis, is another possibility. Check with your baby's doctor for a diagnosis.