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The syndrome is rare: about 100 cases have been described in the literature. About 30% are stillborn, and the majority of those live-born die of the complications of pulmonary hypoplasia.

Failure of normal deglutition results in polyhydramnios, and a lack of movement of the diaphragm and intercostal muscles leads to pulmonary hypoplasia. The lack of normal fetal movement also results in a short umbilical cord and multiple joint contractures. Ulnar deviation of the hands, rocker-bottom feet, camptodactyly, sparse dermal ridges and absence of palmar flexion creases are the other components of the fetal akinesia sequence. The face is expressionless, with hypertelorism, telecanthus and poorly folded, small, and posteriorly angulated ears, and the mouth is small with micrognathia and high-arched palate. Cleft palate and cardiac defects may occur occasionally. Many of these babies are born prematurely, and even when born at term their growth is delayed, they have a short neck and cryptorchidism. If they survive, they are likely to develop short-gut syndrome with malabsorption.

The Pena-Shokeir syndrome is not a unitary entity but is etiologically heterogeneous. Maternal myasthenia gravis has been diagnosed in some cases, and experiments in animal models show that curarization of the mother induces fetal akinesia. All plausible causes of fetal immobility should be searched for (myogenic, neurogenic, ischemic/anoxic), with biopsies when possible.

There are similarities between Pena-Shokeir syndrome type I and the trisomy 18 syndrome: both may include multiple ankyloses, camptodactyly, and rocker-bottom feet. Karyotyping permits differential diagnosis.

Prenatal diagnosis after the birth of an index case relies on ultrasound, which may reveal polyhydramnios, ankyloses, scalp oedema, and decreased chest movements in a fetus with pulmonary hypoplasia.

Autosomal recessive inheritance (with parental consanguinity and/or recurrence in sibs) has been implied in about 50% of the published cases. The heterogeneity makes accurate recurrence risk counselling difficult. A 0.01 to 25% risk for recurrence seems most appropriate in apparently sporadic cases.