An increase in height of the medial longitudinal arch of the foot that does not flatten on weight bearing (i.e., a distinctly hollow form of the sole of the foot when it is bearing weight).

Weakness of the muscles of the arms.

Weakness of the muscles responsible for dorsiflexion of the foot, that is, of the movement of the toes towards the shin. The foot dorsiflexors include the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus, and the peroneus tertius muscles.

Weakness or partial paralysis in the lower limbs.

Absence of neurologic reflexes such as the knee-jerk reaction.

An abnormal gait pattern that arises from weakness of the pretibial and peroneal muscles due to a lower motor neuron lesion. Affected patients have footdrop and are unable to dorsiflex and evert the foot. The leg is lifted high on walking so that the toes clear the ground, and there may be a slapping noise when the foot strikes the ground again.

An abnormal reduction in sensation in the distal portions of the extremities.

A reduction in the speed at which electrical signals propagate along the axon of a neuron.

The presence of an abnormal lateral curvature of the spine.

Reduced strength of the musculature of the distal extremities.

Muscular atrophy affecting muscles in the distal portions of the extremities.

Electromyographic (EMG) findings characteristic of axonal neuropathy, with normal or slightly decreased nerve conduction velocities, normal or slightly prolonged distal latencies, but significantly reduced motor potentials and sensory amplitudes. There may be spontaneous activity upon needle EMG studies, such as increased insertional activity, positive sharp waves, and fibrillation potentials.

Congenital dysplasia of the hip (CDH) is an abnormality of the seating of the femoral head in the acetabulum. Its severity ranges from mild instability of the femoral head with slight capsular laxity, through moderate lateral displacement of the femoral head, without loss of contact of the head with the acetabulum, up to complete dislocation of the femoral head from the acetabulum. It is one of the most common skeletal congenital anomalies (summary by Sollazzo et al., 2000). Acetabular dysplasia is an idiopathic, localized developmental dysplasia of the hip that is characterized by a shallow hip socket and decreased coverage of the femoral head. Its radiologic criteria include the center-edge angle of Wiberg, the Sharp angle, and the acetabular roof obliquity. Most patients with acetabular dysplasia develop osteoarthritis (165720) after midlife, and even mild acetabular dysplasia can cause hip osteoarthritis (summary by Mabuchi et al., 2006). CDH occurs as an isolated anomaly or with more general disorders represented by several syndromes and with chromosomal abnormalities such as trisomy 18 (Wynne-Davies, 1970). Genetic Heterogeneity of Developmental Dysplasia of the Hip Developmental dysplasia of the hip-1 (DDH1) maps to chromosome 13q22; DDH2 (615612) maps to chromosome 3p21. DDH3 (620690) is caused by mutation in the LRP1 gene (107770) on chromosome 12q13.