Pseudohypoparathyroidism as a rare cause of bilateral slipped capital femoral epiphysis
An 8-year-old female presented to the emergency department with a 4 day history of right hip pain and limping. The pain was of spontaneous onset without any history of trauma. She achieved normal milestones till the age of 6 years. Her past medical history was significant for psoriasis, controlled by topical medications. Dietary history revealed a normal intake of a balanced nonvegetarian diet.\nOn examination, she was noted to have skin lesions due to mild psoriasis. There were no phenotypic features of Albright's hereditary osteodystrophy (AHO) which is PHP type 1a. Her weight was 25.8 kg (50th percentile for age and sex), height 131 cm (75th percentile for age and sex), with a height velocity of 4.25 cm/year. Examination of her lower limbs showed a painful right hip with minimal shortening and restricted external rotation. Biochemical investigations revealed low serum calcium and high alkaline phosphatase []. The liver enzymes, coagulation screen, renal function tests, serum phosphorus, serum albumin, and serum magnesium were all within normal limits. Radiological investigations showed grade 2 SCFE on the right side and grade 1 on the left side according to Southwick's classification [Figures and ]. Clinically, she had stable slips according to Loder's classification.\nThe operative treatment planned was in situ pinning of both hips using cannulated screws. The right hip was operated on within 24 h of presentation and the asymptomatic left hip was operated 2 weeks later. Due to her small bony anatomy, 5 mm cannulated screws were used for fixation on both sides. The procedure was otherwise similar to the technique described by Loder. The early postoperative recovery was uneventful and postoperative radiographs were satisfactory. The patient was discharged with advice to eat a calcium rich diet and to take calcium supplements and vitamin D3 (cholecalciferol). As the patient was feeling better, she did not come for the followup appointments. At the 4th postoperative month, she presented with the complaint of pain in her left knee. Clinically her left knee had 5° more valgus than her asymptomatic right knee. Radiographs of both knees showed widening of the lateral distal femoral physis with abnormal ossification within the metaphysis []. Radiographs of the hips revealed a similar appearance to the postoperative radiographs.\nAt this stage, the bone profile showed persistent low calcium levels with elevated alkaline phosphatase, in spite of treatment with calcium and vitamin D3[]. This persistent hypocalcemia prompted us to carry out further endocrinologic evaluation. Her parathyroid hormone (PTH) level was 172 pg/mL (normal range is 10–60 pg/mL). Further investigations revealed normal thyroid function.\nThe combination of high PTH and low calcium with no possible explanation led us to suspect end organ resistance to PTH, which is known as PHP. The absence of AHO phenotype favoured the diagnosis of PHP type 1b. The patient was referred to a geneticist and an endocrinologist for further evaluation. Genetic testing revealed GNAS1 methylation defects, confirming the diagnosis of PHP type 1b. She was started on calcium carbonate supplements and alfacalcidol (1-alpha-hydroxyvitamin D3) 0.5 μg once daily. In a week, her sense of general well being improved and there was a marked reduction in the left lower limb pain. Her serum calcium and vitamin D level increased, and at the same time, serum alkaline phosphatase and PTH levels decreased []. The alfacalcidol dose was slowly increased at weekly increments of 0.5 μg to a final dose of 1.5 μg once daily. She was allowed to bear weight in 1 month.\nAt her last follow up, 2 years after the in situ fixation, the patient remained without symptoms. Radiographs of the hips showed good remodeling of the proximal femur with no evidence of avascular necrosis [Figure , and ,]. Radiographs of her distal femur showed improved ossification and narrowing of the distal femoral physis []. The valgus deformity in her left knee had also improved, but correction with hemiepiphysiodesis may be required in the future. The patient was advised to continue calcium carbonate and alfacalcidol lifelong. Followup till skeletal maturity was planned, but unfortunately the family was lost to followup.