Vitamin D deficiency with secondary hyperparathyroidism is common in South-east Asia. In contrast, primary hyperparathyroidism is relatively rare. We present a case of severe proximal myopathy with significant diagnostic delay.
A 23-year-old lady presented with a 2 years history of lower back pain, radiating to both groins and upper thighs associated with recurrent falls. Her pain and weakness progressed insidiously leading to difficulty standing or walking independently. She had been admitted under orthopedics and neurology at different hospitals where MRI spine/thigh and nerve conduction studies were normal, but serum calcium was low. She was diagnosed with lumbago and sciatica. Management was four glasses of milk/day, ultrasonic massage and physiotherapy. Examination revealed proximal muscle weakness of the limbs, waddling gait, generalized bony tenderness, and bilateral genu valgus. Investigations showed 25OH-vitamin D <4 ng/ml, PTH 898 (1565) pg/ml, phosphorus 1.5 (2.54.9) mg/dl, magnesium 1.9 (1.82.4) mg/dl, calcium 10.0 (8.510.1) mg/dl, CK 20 (2115) IU/l, ALP 1959 (50136) IU/l, 24 h urinary calcium 264 mg/dl, and 24 h urinary phosphorus 0.4 (0.41.3) g/24 h. She was commenced on vitamin D and phosphate. At follow-up, there was significant improvement in symptoms, particularly bony pain, ALP improved (1251 IU/l) but serum calcium and PTH increased to 10.9 mg/dl and 1161 pg/ml respectively. She was diagnosed with myopathy secondary to osteomalacia, primary hyperparathyroidism and hypophosphatemia. Neck USS and Sestamibi scan elucidated a 2.0×1.3×1.1 c right inferior parathyroid adenoma. BMD revealed severe osteoporosis (Z-score L24: −4.7, femoral neck −3.9, forearm −5.7). She underwent Rt inferior parathyroidectomy. Recent biochemistry shows PTH 38.4 pg/ml and calcium 8.8 mg/dl on ergocalciferol 2000 IU/day and Calcium 1000 mg/day. Her symptoms subsided, except genu valgus, and she is independent and working.
Discussion: Myopathy has a wide spectrum of aetiological factors. Our patient had severe osteomalacia, hypophosphatemia and primary hyperparathyroidism. All of these conditions cause myopathy of variable severity. In our patient, its difficult to determine the predominant aetiological factor. Myopathy due to metabolic causes is treatable and requires prompt diagnosis.