Three cases of juvenile onset HTLV-I-associated myelopathy with pseudohypoparathyroidism

Among 201 patients diagnosed with HAM/TSP at Kagoshima University, 21 juvenile onset patients had manifested clinical signs and symptoms at less than 15 years of age. They appeared to have common characteristics such as short stature and slight mental retardation. These signs prompted us to investigate five of them endocrinologically; and three patients with pseudohypoparathyroidism (PHP) were confirmed. Serum calcium levels were low, and human parathyroid hormone (PTH) infusion (Ellsworth-Howard test) caused low response in urinary cyclic AMP and phosphorus excretion. The first case had IgA nephropathy, which is generally associated with infectious diseases, while the second case had muscular lymphocytic infiltration. The mothers of cases 1 and 2, who were both seropositive for HTLV-I, were suspected to have abnormal calcium metabolism based on Ellsworth-Howard test. A brother of case 1 and two sisters of case 3 had also HAM/TSP and short stature. The early clinical onset of HAM/TSP may be due to PTH receptor anomaly and a low level of 1,25-dihydroxyvitamin D, which is deficient in PHP and is involved in the regulation of the immune response. The association with IgA nephropathy or myositis may result from progressive HTLV-I infection.