Lentiginosis

Lentiginosis refers to a condition characterized by an abnormal proliferation of lentigines, which are small, benign, pigmented spots on the skin. These spots are similar in appearance to freckles, but unlike freckles, lentigines do not fade in the absence of sun exposure. Lentiginosis can occur as an isolated phenomenon or as part of a syndrome, and its manifestations can range from a few scattered lentigines to hundreds of spots covering the body.

Causes and Pathogenesis

The development of lentigines is primarily related to a combination of genetic factors and sun exposure. Lentigines arise from melanocytes, the cells responsible for producing melanin, the pigment that gives skin its color. In lentiginosis, there is an increased proliferation of melanocytes at the dermo-epidermal junction. This condition can be idiopathic, meaning it occurs without a known cause, or it can be associated with various genetic syndromes, such as Peutz-Jeghers syndrome, LEOPARD syndrome, and Carney complex.

Clinical Features

Lentigines are typically small, darkly pigmented spots that may appear anywhere on the body but are most commonly found on sun-exposed areas. They are usually round or oval, sharply demarcated, and range in color from light brown to black. Unlike melanoma, lentigines have a uniform color and regular borders. In syndromic lentiginosis, additional features may be present depending on the specific syndrome, such as gastrointestinal polyps in Peutz-Jeghers syndrome or cardiac abnormalities in LEOPARD syndrome.

Diagnosis

The diagnosis of lentiginosis is primarily clinical, based on the appearance and distribution of the lentigines. Dermoscopy, a non-invasive imaging technique, can be helpful in distinguishing lentigines from other pigmented lesions. In cases where a genetic syndrome is suspected, genetic testing may be performed to identify specific mutations. Histopathological examination of a biopsy specimen can confirm the diagnosis, showing an increased number of melanocytes at the dermo-epidermal junction.

Treatment

Treatment of lentiginosis is usually not necessary unless the lesions are cosmetically concerning to the patient. Options for cosmetic treatment include laser therapy, cryotherapy, and topical bleaching agents. It is important for patients with lentiginosis, especially those with extensive sun-exposed lentigines, to practice strict sun protection to minimize the risk of skin cancer. In cases of syndromic lentiginosis, management also involves surveillance and treatment of associated systemic manifestations.

Prognosis

The prognosis for individuals with lentiginosis is generally good, as the condition itself is benign. However, there is an increased risk of skin cancer, particularly melanoma, in individuals with a large number of lentigines. Regular skin examinations are recommended to monitor for any changes in the lentigines that may suggest malignant transformation.