The pheochromocytomas are an important cause of secondary hypertension. Although pheochromocytoma susceptibility may be associated with germline mutations in the tumor-suppressor genes VHL and NF1 and in the proto-oncogene RET, the genetic basis for most cases of nonsyndromic familial pheochromocytoma is unknown. Recently, pheochromocytoma susceptibility has been associated with germline SDHD mutations. Germline SDHD mutations were originally described in hereditary paraganglioma, a dominantly inherited disorder characterized by vascular tumors in the head and the neck, most frequently at the carotid bifurcation. The gene products of two components of succinate dehydrogenase, SDHC and SDHD, anchor the gene products of two other components, SDHA and SDHB, which form the catalytic core, to the inner-mitochondrial membrane. Although mutations in SDHC and in SDHD may cause hereditary paraganglioma, germline SDHA mutations are associated with juvenile encephalopathy, and the phenotypic consequences of SDHB mutations have not been defined. To investigate the genetic causes of pheochromocytoma, we analyzed SDHB and SDHC, in familial and in sporadic cases. Inactivating SDHB mutations were detected in two of the five kindreds with familial pheochromocytoma, two of the three kindreds with pheochromocytoma and paraganglioma susceptibility, and 1 of the 24 cases of sporadic pheochromocytoma. These findings extend the link between mitochondrial dysfunction and tumorigenesis and suggest that germline SDHB mutations are an important cause of pheochromocytoma susceptibility.

Recent data from murine models have confirmed that Langerhans cells are not the only population of APCs in the skin involved in initiating immune responses. In healthy human skin, we identify CD1a+ dermal APCs located close to the lymphatic vessels in the upper layers of the dermis that are unequivocally distinct from migrating Langerhans cells but exhibit both potent allostimulatory capacity and a chemotactic response to CCR7 ligands. In contrast, CD14+ dermal APCs are distributed throughout the dermis and lack a chemotactic response to CCR7 ligands. CD1a+ dermal APCs therefore represent an APC population distinct from Langerhans cells that are capable of migrating to lymph nodes and stimulating naive T cells. In humans, CD1a+ dermal APCs may fulfill some of the roles previously ascribed to Langerhans cells.

Loss of circadian variation in blood pressure is associated with an increased mortality rate, regardless of diabetes type. The combination of non-dipping and subsequent renal impairment leads to the highest mortality rate. The study suggests a role for ambulatory blood pressure monitoring in day-to-day clinical practice to select patients with nephropathy who are at greatest risk, in an effort to alter outcome.

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SDH-B mutation carriers develop disease early and predominantly in extra-adrenal locations. Disease penetrance is incomplete. Metastatic disease is prominent but levels are less than previously reported. Clinical manifestations may include papillary renal cell carcinoma and macrovascular disease.