Hypoparathyroidism mimicking ankylosing spondylitis and myopathy: a case report

Idiopathic hypoparathyroidism (HP) is an induced or inherited condition characterized by insufficient secretion of parathyroid hormone. The clinical manifestations of this condition are varied, and pain and stiffness affecting the back and hips resembling ankylosing spondylitis is an under-recognized symptom in these patients. Here, we report a case of delayed diagnosis of hypoparathyroidism referred to a rheumatologist due to progressive inflammatory back pain and myalgia. Idiopathic hypoparathyroidism is an induced or inherited condition of unknown etiology and is characterized by insufficient secretion of parathyroid hormone due to atrophy or absence of parathyroid glands, which leads to hypocalcaemia and hyperphosphatemia. Hypoparathyroidism has multiple clinical manifestations, which primarily involve tissues of ectodermic origin. Pain and stiffness affecting the back and hips, limited movement and posture resembling that seen in patients with ankylosing spondylitis is an under-recognized feature in patients with this condition. Muscular complaints by these patients are common because the concentration of calcium ions is important for the maintenance and control of several biochemical processes during muscle contraction. Hypocalcaemia causes hyperexcitability of nerves and muscles, and a sporadic increase in muscular enzymes. Here, we report a case of delayed diagnosis of hypoparathyroidism referred to a rheumatologist due to progressive inflammatory back pain and myalgia with concomitant elevation of inflammatory markers and muscle enzymes. The patient was initially erroneously diagnosed with ankylosing spondylitis (AS) and idiopathic myopathy. This case reinforces the relevance of investigating the underlying mineral metabolism disturbances in patients with inflammatory diseases.