The diagnosis of Werdnig-Hoffmann disease is confirmed by DNA study. The genetic abnormality is at the 5q 11.2-13.2 site. Neonates with the clinical findings of Werdnig-Hoffmann disease and a negative DNA study should undergo EMG, nerve conduction, tensilon trial, and muscle biopsy to exclude the possibility of other causes of hypotonia with decreased dynamic tone. The EMG of a neonate with Werdnig-Hoffmann disease shows fibrillation potentials. Fasciculations are rare. Occasionally a peculiar pattern of spontaneous bicouple discharges may be present. Muscle biopsy may show panfascicular atrophy and type I fiber hypertrophy. The loss of checkerboard appearance and the presence of type grouping that is characteristic of Werdnig-Hoffmann disease during childhood is not present in most neonates with Werdnig-Hoffmann disease. The only treatment for neonates with Werdnig-Hoffmann disease is supportive.

Spinal Muscular Atrophy with Respiratory Distress Type 1
Neonates with Spinal Muscular Atrophy with Respiratory Distress Type 1 look the same as neonates with Spinal Muscular Atrophy (Werdnig-Hoffmann disease). The features that distinguish spinal muscular atrophy respiratory distress type 1 are diaphragmatic weakness, distal limb wasting, distal arthrogryposis and bulky proximal fingers (Figure 32.1). Diaphragmatic weakness may lead to apnea and respiratory distress. Spinal Muscular Atrophy with Respiratory Distress Type 1 is due to a mutation in the gene encoding inmunoglobulin mu-binding protein 2. This gene is located on chromosome 11.

A	B

Figure 132.1.— [A] The bulky proximal digits (prominent fat pad) contrast with the wasted appearance of more distal regions of the fingers. [B] Right diaphragmatic paralysis.

Pompe Disease
Pompe disease or acid maltase deficiency occurs less frequently than Werdnig-Hoffmann disease. The gene locus is at the 17q 23-25 site. Pompe disease is an autosomal recessive disorder caused by alpha-glucosidase deficiency. Alpha-glucosidase deficiency leads to increased glycogen deposition in lysosomes of many different tissues, including the anterior horn motor neurons and muscle. The most common clinical manifestations are hypotonia with decreased dynamic tone (without the typical distribution of Werdnig-Hoffmann disease), congestive heart failure, a large tongue, bulky muscles, and a firm liver. The deposition of glycogen in the cardiac muscle lysosomes leads to a large heart with shortened PR intervals, elevated R-waves, and inverted T-waves. Muscle biopsy reveals large amounts of periodic acid Schiff (PAS)-positive material. The enzymatic defect can be demonstrated in leukocytes and fibroblasts. Prenatal diagnosis from amniotic fluid fibroblasts is possible. There is no specific treatment. Death due to cardiac failure often occurs at a young age.