Andersen's syndrome is characterized by periodic paralysis, cardiac arrhythmias, and dysmorphic features. We have mapped an Andersen's locus to chromosome 17q23 near the inward rectifying potassium channel gene KCNJ2. A missense mutation in KCNJ2 (encoding D71V) was identified in the linked family. Eight additional mutations were identified in unrelated patients. Expression of two of these mutations in Xenopus oocytes revealed loss of function and a dominant negative effect in Kir2.1 current as assayed by voltage-clamp. We conclude that mutations in Kir2.1 cause Andersen's syndrome. These findings suggest that Kir2.1 plays an important role in developmental signaling in addition to its previously recognized function in controlling cell excitability in skeletal muscle and heart.

Andersen syndrome is a rare entity and comprises potassium sensitive periodic paralysis, ventricular arrhythmia, and an unusual facial appearance; syncope and sudden death have also been reported. The recognition of the characteristic face permits an early diagnosis in order to detect the severe systemic manifestations that are associated with this syndrome. The genetic defect is not linked to any other form of potassium sensitive periodic paralysis nor is it related to that of the long QT syndrome; nevertheless, a prolonged QT interval can be detected in a significant proportion of the cases. Sixteen cases of this syndrome have been described. We report on a three-generation family with 10 affected members. To our knowledge, this is the largest number of cases reported in one family. We noted some additional minor anomalies such as broad forehead and malar hypoplasia. Our patients had variable expression in the classical triad and of the severity of the systemic manifestations. Five of 8 affected studied members did not have a long QTc, which has been suggested as a constant finding in this syndrome.

Congenital generalized hypertrichosis terminalis has been described in association with other features as gingival hyperplasia, osteochondrodysplasia, and a dysmorphic face. Bondeson and Miles [1993: Am J Med Genet 47:198-212] described a woman with universal congenital hypertrichosis terminalis associated with gingival hyperplasia; the face of this patient was coarse and different from other forms of hypertrichosis described before. We present an 11-year, 6-month-old girl with universal congenital hypertrichosis terminalis, gingival hyperplasia, and a characteristic coarse face resembling the patient described by Bondeson and Miles [1993: Am J Med Genet 47:198-212]. We propose that this type of congenital generalized hypertrichosis terminalis, associated with gingival hyperplasia and a coarse face, is a distinctive new entity.

The human Sonic Hedgehog gene (SHH) is one of the vertebrate homologs related to the Drosophila segment polarity gene hedgehog. The entire coding and promoter region of the SHH gene, including 2 kb 5' of the transcriptional start site has been screened for mutations in families with autosomal dominant sacral agenesis and autosomal dominant triphalangeal thumb, two conditions previously known to be linked to 7q36. We have also studied the SHH gene in five families with mirror polydactyly associated with tibial hemimelia and in 51 unrelated patients with neural tube defects. Except for two sequence variants in exon 3, no mutations were found in these disease categories. OFF

Idiopathic osteolysis denotes a group of rare bone disorders differentiated on the basis of clinical, radiological, and genetic criteria. Idiopathic multicentric osteolysis (IMO) is one form of osteolysis that can occur as an autosomal dominant condition. In childhood, affected individuals have arthritic-like episodes, followed by progressive deformities, radiological osteolytic changes, and variable degrees of disability. A peculiar face and variable renal involvement have been described as associated manifestations. We report on a family with three members affected by IMO in two generations showing variable bone changes and persistent proteinuria. A sporadic case with severe renal damage is also described in which a de novo dominant mutation is suggested. All patients had peculiar facial manifestations including triangular shape, protruding eyes, and micrognathia. These manifestations may be part of the syndrome of IMO.