Systemic Illness
Generalized hypotonia due to systemic illness occurs acutely and usually improves as the systemic illness improves. Nevertheless, occasionally the improvement in postural tone lags behind the general improvement and in these cases the possibility of a neuromuscular disorder is often raised. Usually a few days of observation is all it takes to differentiate generalized hypotonia due to systemic illness from generalized hypotonia due to a neuromuscular disorder. The dynamic tone of a neonate with hypotonia due to systemic illness is normal or decreased. Frequent causes of hypotonia due to systemic illness are sepsis, hypoglycemia and rickets.
Rickets usually occurs in premature neonates but may also occur in full term neonates. The clinical manifestations of neonatal rickets are: hypotonia, enlarged fontanel, widened cranial sutures, frontal bossing and rachitic rosary (Figure 102.1 [A]). Radiological findings include prominent chostocondral junctions and epiphyseal flaring and widening (Figure 102.1 [B]). The triad of rachitic rosary, low 25-hydroxyvitamin D and high alkaline phosphatase is diagnostic of neonatal rickets.

A	B

Figure 102.1.— [A] Rachitic rosary noted few days after birth; [B] epiphyseal flaring and widening