Question

There are three overlapping clinical syndroms associated with deficiencies in HGRT activity. Individuals with at least 8% activity of normal individuals present with overproduction of uric acid and associated gout, a condition called Kelley-Speegmiller syndrome. Patients with 1.5%-8% have neurological disability that ranges from clumsiness to debilitating motor dsyfunction in addition to uric acid overproduction problems. Patients with less than 1.5% HGPRT activity have Lesch-Nyhan syndrom. Provide possible explanations for the differences in HGPRT activity in the different syndromes.

Answer 1

HPRT deficiency is associated with both qualitative and quantative spectrum of abnormalities. Patients may exhibit (1) hyperuricemia due to overproduction of Uric acid; (2) Motar disfunction, including dystonia (3) Selective cognitive impairment, (4) Aberrant behaviour, (5) growth retardation and anemia.

These all cases depend on activity of HPRT enzyme in body which determines the pattern of abnormalities in patient and severity of case. For example, No residual enzyme exhibit Lesch-Nyhan syndrome while, partial activity leads to hyperuricemia disease.

HPRT deficiency is also associated with dysfunction of dopamine system in gangliaon which may another possible cause for other neurobehaviourial fetures in patient.

HPRT expression on the mRNA and protein level is induced by hypoxia inducible factor 1 which is directly associated with array of cellular responses that are used for adaptation during oxygen deprivation. Therefore, HPRT is a critical pathway that helps preserve the cell's purine nucleotide resources under hypoxic conditions as found in pathology such myocardial ischemia.