For five years, a 12-year-old boy has had an expanding, asymptomatic lesion on his left thigh and knee. There was no known precipitating event—no trauma or insect bite. No other areas are involved. The boy’s health is otherwise good.

On examination, a 20 x 10–cm “lesion” is noted on the left medial thigh and knee. The entire area is surprisingly firm to the touch and is brownish blue, with a sclerotic look and feel. There is a central area of depression that, at its deepest, is at least 2 cm lower than the surrounding skin. The area is covered by a cicatricial fusiform plaque measuring 8 x 3 cm. The overlying skin is remarkably smooth. The courses of the subcutaneous venous plexus can be easily traced through the atrophic skin. The pathologic process covers the medial thigh, crosses the joint, and is (based on the history) extending inferiorly in a somewhat linear configuration. No other areas of involvement are appreciated, and the patient’s skin is otherwise normal.

In an effort to avoid the creation of a nonhealing wound, a 5-mm punch biopsy is performed on the wall of the depressed area, avoiding the central cicatricial portion. The results are as follows: thickening and homogenization of collagen bundles concentrated in the lower reticular dermis.

ANSWER
The one incorrect statement is choice “a,” since morphea does not progress into systemic sclerosis (SS), although the local histologic process is almost identical in each. Morphea—especially in children, and especially with linear types that course over crucial structures such as joints or faces—can interfere with normal function and growth, making choice “b” correct. Several theories have arisen to explain the genesis of this disease, including an autoimmune basis; to date, none has been proven, so both choice “c” and choice “d” are technically correct.

DISCUSSION
This case is a perfect example of an established maxim of dermatology: One seldom diagnoses what one has never heard of. The reported incidence of morphea is 25 cases per one million Americans, but it is a common enough complaint in dermatology practices.

Although the precise cause is unknown, there is general agreement that morphea represents localized dysregulation of collagen synthesis and deposition in the dermis. While that process is identical to that seen in SS, the two are otherwise not part of the same clinical continuum—good news for the morphea patient, since SS is a far more serious disease. Morphea patients do not, for example, experience the components of SS such as Raynaud’s phenomenon, sclerodactyly, or involvement of internal organs, nor do they share the potentially dire prognosis of SS patients.

Morphea takes several clinical forms; the most common is the plaque type, which typically presents as an annular lesion on the trunk or extremity, with the potential to grow to considerable size. Most will stop growing in time, but the discolored “burnt-out” lesion remains, leaving a purplish brown atrophic area.

Another form of morphea is a linear configuration. This is seen particularly in children, in whom it can interfere with normal growth and function. Examples include the morphea variants Parry-Romberg syndrome and en coup de sabre; both appear on the face, and deeper structures such as soft tissue and bone can be affected.

TREATMENT
This patient has advanced disease, for which calcipotriene cream (to be applied bid for two months) was prescribed, with follow-up to monitor his disease and its effect on the joint as well as the skin. Other medications have been tried for morphea, including minocycline and methotrexate, with decidedly mixed results.