Adducted thumbs: a clinical clue to genetic diagnosis.

Adducted thumbs are an uncommon congenital malformation. It can be an important clinical clue in genetic syndromes, e.g. the L1 syndrome. A retrospective survey was performed including patients with adducted thumbs referred to the Department of Clinical Genetics between 1985 and 2011 by perinatologists, (child) neurologists or paediatricians, in order to evaluate current knowledge on the genetic etiology of adducted thumbs. Twenty-five patients were included in this survey. Additional features were observed in 88% (22/25). In 25% (4/16) of the patients with adducted thumbs and congenital hydrocephalus L1CAM gene mutations were identified. One patient had a mosaic 5p13 duplication. Recommendations are made concerning the evaluation and genetic workup of patients with adducted thumbs.

Ehlers-Danlos arthrochalasia type (VIIA-B)--expanding the phenotype: from prenatal life through adulthood.

The Ehlers-Danlos syndromes (EDS) form a clinically and genetically heterogeneous group of inherited connective-tissue disorders characterized by joint hypermobility, tissue fragility and skin abnormalities. Six subtypes have been well characterized based on clinical features and molecular genetic abnormalities. The arthrochalasia type EDS (formerly types VIIA and B) is characterized by severe generalized joint hypermobility with multiple dislocations including congenital bilateral dislocation of the hips, muscular hypotonia and distinct dysmorphic features. The diagnosis of the arthrochalasia type EDS is of importance in the neonatal period because of consequences of physical disability in later life. However, the differential diagnosis may be difficult because of overlap with other hypermobility syndromes. In addition, the significant hypotonia may direct the physician toward various neuromuscular diagnoses. As patients become older, the hypotonia decreases and facial features become less distinct. In this report, we describe seven patients at different ages. Timing of diagnosis varied from prenatal life to adult age. The diagnosis of EDS type VII was confirmed by biochemical studies or mutation analysis showing characteristic mutations in COL1A1 and COL1A2. These mutations result in skipping of exon 6, which leads to defective collagen synthesis. For physicians treating patients with EDS type VII, achieving mobility for the patient is the greatest challenge and it may be impossible because of recurrent dislocations of nearly all joints in severe cases.

Unique skin changes in a case of Albright hereditary osteodystrophy caused by a rare GNAS1 mutation.

Albright hereditary osteodystrophy (AHO) is a syndrome of short stature, obesity, brachydactyly and subcutaneous calcifications with pseudohypoparathyroidism (PHP; leading to hypocalcaemia, hyperphosphataemia and elevated levels of parathyroid hormone, PTH). It was first described over 60 years ago. Since then, much has been learned about the aetiology of AHO which has been shown to be caused by heterozygous loss-of-function mutations within the GNAS1 gene. GNAS1 is subject to imprinting leading to phenotypic heterogeneity within kindreds with one mutation. Patients with AHO often present with symptoms of hypocalcaemia and/or with subcutaneous calcifications. The latter is thought to be the typical skin abnormality in AHO. We describe a family with AHO and hormone resistance (PHP type Ia) resulting from a rare mutation in GNAS1. The proband presented with small subcutaneous calcifications in the helix of the right ear and concentrated in a sharply demarcated zone of subcutaneous and dermal hypoplasia. This abnormality has so far not been described in patients with AHO. We speculate on the mechanism of dermal hypoplasia and resistance to PTH and suggest that subcutanous or dermal hypoplasia might be another feature which can be present in patients with AHO.