Akarsu A N, Akhan O, Sayli B S, Sayli U, Baskaya G, Sarfarazi M
Department of Medical Biology and Genetics, University of Ankara, Faculty of Medicine, Sihhiye, Turkey.
J Med Genet. 1995 Jun;32(6):435-41. doi: 10.1136/jmg.32.6.435.
Syndactyly type II (synpolydactyly (SPD)) is an autosomal dominant condition with typical abnormalities of the distal parts of both upper and lower limbs. We report here a previously undescribed phenotypic feature of people with severe hand and foot deformities who were born to two affected parents. This is the first example of SPD subjects manifesting a very distinctive phenotype, suggesting that they must be homozygous for this condition. The typical characteristic clinical features in these subjects are as follows: (1) short hands with wrinkled fatty skin and short feet; (2) complete soft tissue syndactyly involving all four limbs; (3) polydactyly of the preaxial, mesoaxial, and postaxial digits of the hands; (4) loss of the normal tubular shape of the carpal, metacarpal, and phalangeal bones, so as to give polygonal structures; (5) loss of the typical structure of the cuboid and all three cuneiform bones while the talus calcaneus and navicular bones remain intact; (6) large bony islands instead of metatarsals, most probably because of cuboid-metatarsal and cuneiform-metatarsal fusions; and (7) severe middle phalangeal hypoplasia/aplasia as well as fusion of some phalangeal structures that are associated with the loss of normal phalangeal pattern. We report seven subjects with this phenotype from three different branches of a very large SPD pedigree exhibiting the same phenotype with minimal variation. In mice, the Polysyndactyly (Ps) mutation shows a pattern of synpolydactyly very similar to that of human SPD, suggesting that they may well be homologous mutations. A molecular genetic study is currently under way to determine the chromosomal location of the SPD locus in humans and to identify the corresponding homologous region in mice.
II型并指（综合征性多指（SPD））是一种常染色体显性疾病，上肢和下肢远端均有典型异常。我们在此报告两个患病父母所生的严重手足畸形患者的一种此前未被描述的表型特征。这是SPD患者表现出非常独特表型的首个例子，表明他们在这种疾病上必定是纯合子。这些患者典型的特征性临床表型如下：（1）手部短小，皮肤有皱纹且脂肪较多，足部短小；（2）所有四肢均有完全性软组织并指；（3）手部拇指、中间指和小指多指；（4）腕骨、掌骨和指骨失去正常的管状形态，形成多边形结构；（5）骰骨和三块楔骨的典型结构消失，而距骨、跟骨和舟骨保持完整；（6）没有跖骨，取而代之的是大的骨岛，很可能是由于骰骨 - 跖骨和楔骨 - 跖骨融合；（7）严重的中节指骨发育不全/发育不良以及一些指骨结构融合，这与正常指骨模式的丧失有关。我们从一个非常大的SPD家系的三个不同分支中报告了七名具有这种表型的患者，他们表现出相同的表型，差异极小。在小鼠中，多指（Ps）突变显示出与人类SPD非常相似的综合征性多指模式，表明它们很可能是同源突变。目前正在进行一项分子遗传学研究，以确定人类SPD基因座的染色体定位，并在小鼠中鉴定相应的同源区域。
