Rare syndromes.

Dermatologists may also encounter patients presenting with skin lesions that reflect an underlying endocrine disorder not commonly seen in daily practice. Some of these endocrine disorders include glucagonoma, neurofibromatosis type 1, McCune-Albright syndrome, multiple endocrine neoplasia, the Carney complex, carcinoid tumors, and mastocytosis. The clinical syndrome classically associated with glucagonoma includes necrolytic migratory erythema, weight loss, diabetes mellitus, anemia, cheilitis, venous thrombosis, and neuropsychiatric symptoms. The hallmarks of neurofibromatosis type 1 are the multiple café-au-lait spots and associated cutaneous neurofibromas. Other presenting features include freckling, peripheral neurofibromas, Lisch nodules, bone abnormalities, tumors, neurologic abnormalities and hypertension. McCune-Albright syndrome is characterized by café-au-lait spots, polyostotic fibrous dysplasia, sexual precocity, and hyperfunction of multiple endocrine glands. Multiple endocrine neoplasia type 2A is characterized by medullary thyroid cancer, pheochromocytoma, and primary parathyroid hyperplasia. In some patients with multiple endocrine neoplasia type 2A, cutaneous lichen amyloidosis may also be present. Multiple endocrine neoplasia type 2B is characterized by medullary thyroid cancer and pheochromocytoma but not hyperparathyroidism. The syndrome also includes mucosal neuromas, typically involving the lips and tongue, intestinal ganglioneuromas and a marfanoid habitus. Multiple endocrine neoplasia type 1 is an autosomal dominant predisposition to tumors of the parathyroid glands (four-gland hyperplasia), anterior pituitary, and pancreatic islet cells; hence, the mnemonic device of the "3 Ps"; multiple cutaneous lesions (angiofibromas and collagenomas) are frequent in patients with multiple endocrine neoplasia type 1. Carney complex may be viewed as a form of multiple endocrine neoplasia because affected patients often have tumors of two or more endocrine glands, including primary pigmented nodular adrenocortical disease (some with Cushing's syndrome), pituitary adenoma, testicular neoplasms, thyroid adenoma or carcinoma, and ovarian cysts. Additional unusual manifestations include psammomatous melanotic schwannoma, breast ductal adenoma, and a rare bone tumor, osteochondromyxoma. Carcinoid syndrome is the term applied to a constellation of symptoms mediated by various humoral factors elaborated by some carcinoid tumors; the major manifestations are diarrhea, flushing, bronchospasm, and cardiac valvular lesions. Mast cell diseases include all disorders of mast cell proliferation. These diseases can be limited to the skin, referred to as "cutaneous mastocytosis," or involve extracutaneous tissues, called "systemic mastocytosis." Patients present with urticaria pigmentosa, mastocytoma, or diffuse cutaneous mastocytosis. Systemic involvement may be gastronintestinal, hematologic, neurologic, and skeletal.