Chapter 118 Hand defects and the eye
The combination of hand and eye defects is frequent and may be observed in a variety of disorders: Duane’s syndrome,1–3 Möbius’ syndrome,2 CHARGE association,4 and many others. There may be genetic causes, including specific genes and/or new mutations,1,5,6 but, due to incomplete penetrance, sporadic events, and association with environmental factors,2 it is not always possible to determine the underlying mechanism.
It is important to consider the embryology of eye and hand development to understand why such defects may occur simultaneously. During the third week of gestation, at about 22 days, the optic primordium becomes identifiable in the human embryo. It is the first morphological evidence of the eyes. At 25 days as the optic cup and embryonic fissure emerge, upper limb buds appear. By 36 days, closure of retinal fissure is almost complete and the retina is incompletely pigmented. At the same time, the hand plate has formed with condensation of mesenchyme. In the hand plate, a central carpal region is surrounded by a crescentic flange, the digital plate, from which originates the five-finger rays. At 45 days, the fingers are partially separated.
The etiology of most limb defects (Table 118.1) is unknown. Familial associations indicate a genetic basis for some cases; however, environmental agents such as drugs2 may be related to the development of limb defects. Developmental abnormalities such as amniotic bands, oligohydramnios, and local vascular disruption are also associated with limb abnormalities.7 Eye defects and hand/finger anomalies originate usually between the third and the fifth week of gestation. Many loci and gene mutations have been associated with hand and eye anomalies.1,4–6
The various hand and eye defects can be grouped according to their similarity in overall features, or according to one major feature among the patterns of malformation, in the same manner as Smith’s recognizable patterns of malformation.8 Many conditions present with occasional hand and eye defects, but only the most important and consistent associations are described in Table 118.2
|Eye/ocular region anomalies
|Down’s syndrome (trisomy 21)
|Upslanting palpebral fissures, epicanthal folds, iris Brushfield’s spots, keratoconus, strabismus, nystagmus, myopia, cataracts
|Short metacarpals and phalanges, fifth finger mid-phalanx hypoplasia, single transverse palmar (Simian) crease
|Short/slanted palpebral fissure, ptosis, hypertelorism, iris coloboma, cataract, microphthalmos
|Clenched hand, overlapping of fingers, absence of distal crease, hypoplasia of nails, hypoplastic or absent thumb, syndactyly, polydactyly, ectrodactyly, short fifth metacarpals
|Trisomy 13 (Patau’s syndrome)