(P30-013-25) Investigating the Cause of Tonic Seizures in a 6-Month Old Female: A Case of Vitamin D Dependent Rickets

Objectives: Rickets can be classified as calcipenic or phosphopenic. Calcipenic rickets may be due to reduced calcium intake or due to hypovitaminosis D. Phosphopenic rickets can be due to reduced phosphate intake or excessive renal loss of phosphate.

Genetic mutations in genes responsible for enzymes involved in Vitamin D activation can cause type 1 or 2 rickets. Clinical features include bone pain, increased tendency of fracture, delayed growth and development, leg bowing. 

Methods: A 5 month old female patient, presented with tonic movements of upper and lower limbs. The child was started on Phenobarbitone. The laboratory investigations showed a negative septic work up and the levels of electrolytes (sodium, potassium) were normal with reduced calcium 6.5mg/dl and ionised calcium 1.01mmol/l levels. The child was treated with calcium supplements 150mg/kg and discharged with a diagnosis of hypocalcemic seizures.

At the age of 6 months the child presented with multiple episodes of seizures lasting for about 3-5 minutes, associated with up rolling of the eyes, frothing of saliva and involuntary movements. Blood investigations showed low calcium( 4.7mg/dl) and ionised calcium (0.58 mol/l) level. The dose of oral calcium supplements was increased to 180 mg/kg because of persistent low calcium levels. The child was monitored with regular follow up in which calcium levels showed almost no improvement, hence intravenous calcium gluconate with oral calcium supplements were administered along with magnesium for 48 hours. A differential diagnosis of hypoparathyroidism was considered but normal PTH levels (385 pg/ml) ruled it out. Post this, oral laretol ( an active form of Vitamin D to treat low levels of calcium) and calcium supplement increased up to 200mg/kg were administered to the patient. Improvement in patients health was seen, this lead to the suspicion of a genetic disorder.

Results: A genetic work up was carried out to corroborate the diagnosis. Genetic analysis demonstrated the evidence of Vitamin D dependent rickets. Thus the patient was advised to stay on lifelong treatment with Vitamin D supplements.

Conclusions: The study highlights a case of Vitamin D dependent rickets, a genetic disorder which weakens the bones. Thus, these patients are given high doses of Vitamin D or laretol to prevent permanent bone deformities and ensure normal growth.

Funding Sources: None