Hyperpigmented Macules: McCune-Albright Syndrome

McCune-Albright syndrome is classically described as a triad of polyostotic fibrous dysplasia, café au lait macules, and precocious puberty. The syndrome may also be accompanied by various other endocrinopathies including hyperthyroidism, acromegaly, hyperprolactinemia, Cushing syndrome, and hypophosphatemic rickets. Some patients may also exhibit hepatic, cardiac, and GI dysfunction.

The syndrome is more common in girls than boys, but both sexes are affected. It is caused by a mutation in the alpha subunit of a G protein. This mutation results in increased signal transduction along the cAMP pathway, which stimulates growth and function of the gonads, adrenal cortex, specific pituitary cell populations, osteoblasts, and melanocytes.

The hyperpigmented lesions in McCune-Albright syndrome are classically described as "coast of Maine" macules with broad, irregular borders. The 14-year-old patient pictured here demonstrates a characteristic macule. These lesions are typically larger than macules in other conditions and are often found over the sacrum, buttocks, and upper spine. As a rule, fewer than 6 lesions are present. About half of the time, they are unilateral and follow the lines of Blaschko (see case on page 7). If the lesions are unilateral, they are usually found on the same side on which the skeletal abnormalities are more prominent.