Oral motor dysfunction and feeding difficulties in nephropathic cystinosis

Nephropathic cystinosis is a genetic disorder in which the amino acid cystine accumulates in lysosomes, resulting in multiorgan dysfunction. Progressive neuromuscular dysfunction, with bulbar and upper extremity weakness, has been described in adults with this disorder. The purpose of the present study was to determine whether there was evidence of early bulbar involvement, suggested by feeding difficulties or oral motor dysfunction in these patients, and whether the feeding and oral motor problems were associated with other evidence of neurologic dysfunction. Twenty-two children and adolescents with nephropathic cystinosis were studied. Parents completed questionnaires on feeding history and oral motor problems. Eighteen patients were given an oral motor examination, and 14 received a complete neurologic examination. The majority of children had a history of feeding difficulties. Seven children required a gastrostomy tube. Abnormalities on oral motor examination included hypotonia, abnormal gag reflex, and throaty or congested voice. Abnormalities on neurologic examination included hypotonia, muscle weakness, gross and fine motor dysfunction, and ataxia. The results indicate that feeding difficulties and oral motor dysfunction are common in children with cystinosis and appear to correlate with the general degree of neurologic dysfunction. Long-term follow-up is necessary to determine whether the early oral motor problems predict the later development of the progressive myopathy observed in adults with cystinosis.