ESPE Abstracts

Introduction: Nephropathic cystinosis is a rare inherited lysosomal storage disorder due to mutation in CTNS gene. Cystinosis metabolic bone disease (CMBD) represents an evident multifactorial problem in those patients necessitating multidisciplinary team approach.

Methods: Prospectively eighteen patients with infantile nephropathic cystinosis had been recruited from Cystinosis Clinic, Children's Hospital, Cairo University. Plain X ray on both upper and lower limbs, skull, spine, left hand was performed to all patients. Laboratory assessment of bone profile included calcium, phosphorus, alkaline phosphatase, parathormone (PTH) hormone and 25-hydroxyvitamin D were measured.

Results: The age of recruited patients ranged from 0.8 to 10.6 years. X- ray of both upper and lower limbs revealed osteopenia and osteosclerosis in all 18 patients (100%), while rachitic manifestations were found in 6 patients (33.3%),14 patients (77.7%) had delayed bone age and 2 patients (11.4%) had pathological fractures. Regarding skull and spine radiological findings, four patients (22.2%) had spine osteopenia, while 2 patients (11.1%) had spine osteosclerosis and spine bone deformities and 1 of them (5.6%) had vertebral fracture. Median level of 25- hydroxyvitamin D was 24.35 ng/dl which was below the sufficient level. 25 OH vitamin D3 was deficient in 4 patients (22.2%), insufficient in 7 patients (38.9%) and sufficient in 7 patients (38.9%). PTH level was high with median level (30.91ng/dl) above the normal range. Hypocalcemia was reported in 8 patients (44.4%) and 6 patients (33.3%) had hypophosphatemia. The study showed that the age of starting cysteamine therapy had a positive correlation with PTH (P-value 0.039, r =0.48).

Conclusion: Patients with nephropathic cystinosis have significant bone manifestations with wide spectrum could be detected by plain X-ray. Regular assessment of skeletal status, growth and bone deformities is mandatory. The early diagnosis and prompt treatment with cyteamine also adequate replacement of urinary losses can reduce the severity of CMBD.

Key words: Nephropathic cystinosis, Skeletal manifestations, Parathormone hormone, Phosphorus, Plain X ray.