[Adult-onset Hartnup disease presenting with neuropsychiatric symptoms but without skin lesions].

Hartnup disease is an inborn abnormality of renal and intestinal transport involving the neutral amino acids. Intermittent pellagra-like rash, attacks of cerebellar ataxia and psychiatric disturbance are characteristic symptoms of this disease. We described here a patient with adult-onset Hartnup disease who presented unique neuropsychiatric symptoms but no dermatologic symptoms, and reported features of amino acids transport in this patient and his family. The patient, a man aged 37 years, was referred to us because of lasting daytime bruxism. He is the second child of healthy parents who are first cousin; his elder brother who has been mentally retarded became bed-ridden and died at 32 years of age. His younger brother is completely healthy. Although the patient's development in infancy has been slightly retarded, he completed compulsory 9-year education. At 29 years of age, he experienced episodes of diplopia, ataxic gait and insomnia, and at 33 years of age, of transient stupor. There had been no history of photosensitivity or dermatitis. On neurological examination, there were trunkal ataxia, increased muscular tone and decreased mental activity besides bruxism. These symptoms remained unchanged despite of several medications including trihexyphenidyl, diazepam, halloperidol, tiapride and sulpiride. Two months later, the patient became stuporous; bruxism and hypertonicity became exaggerated. Myerson's sign, sucking reflex and grasp reflex in both hand appeared. There was no dermal lesion. A cranial computed tomography revealed a small calcification in the right frontal subcortical region and a single photon emission tomography indicated possible bifrontal hypoperfusion. Electroencephalograms demonstrated non-specific slowing. Somatosensory evoked potentials and nerve conduction velocities were normal. There were constant indicanuria and amino-aciduria.(ABSTRACT TRUNCATED AT 250 WORDS)

The Hartnup phenotype: Mendelian transport disorder, multifactorial disease.

The Hartnup mutation affects an amino acid transport system of intestine and kidney used by a large group of neutral charge alpha-amino acids (six essential and several nonessential). We compared developmental outcomes and medical histories of 21 Hartnup subjects, identified through newborn screening, with those of 19 control sibs. We found no significant differences in means of growth percentiles and IQ scores between Hartnup and control groups (but all low academic performance scores were found in the Hartnup group, and various skin lesions occurred in five Hartnup subjects), no significant difference between means of the summed plasma values for amino acids affected by the Hartnup gene in Hartnup and control groups, two Hartnup subjects with clinical manifestations--impaired somatic growth and IQ in one, impaired growth and a "pellagrin" episode in the other--who had the lowest summed plasma amino acid values in the Hartnup group; the corresponding values for their sibs were the low outliers in the control group, and two tissue-specific forms of the Hartnup (transport) phenotype: renal and intestinal involvement (15 families) and renal involvement alone (one family), both forms having been inherited as autosomal recessives (the symptomatic probands had the usual form). Whereas deficient activity of the "Hartnup" transport system is monogenic, the associated plasma amino acid value (measured genotype) is polygenic. The latter describes the parameter of homeostasis and liability to disease. Cause of Hartnup disease is multifactorial.