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Myopathy associated with hypothyroidism classically presents with proximal weakness, fatigue, exertional pain, slowed movement, diminished deep reflexes, stiffness, myalgia, myoedema, and less commonly, cramps. Rarely, muscle enlargement is also seen, and the term Kocher Debre Semelaigne syndrome (KDS syndrome) is used.1–3
We report the case of an 11 year old boy presenting with poor growth, mental retardation, diffuse exertional pain in both lower limbs, and progressive difficulty in squatting for six months. There was no family history. On examination he showed coarse facies, large tongue, athletic build, with height 110 cm and weight 22 kg. His IQ was assessed as 60, power in proximal group of muscle was Grade III, and calf muscles showed firm enlargement with delayed deep tendon reflexes.
Investigation showed normal haemotology and renal function, electrocardiogram, and skull and chest x rays. Serum thyroxine was 72 nmol/L (n = 64–154 nmol/L), serum triiodothyronine was 1.8 nmol/L (n = 1.1–2.9), serum thyroid stimulating hormone = 10.0 mU/l (n = 0.4–5.0 mU/l) and serum creatine phosphokinase was 2246 U/ml (n = 35–145 U/ml). Muscle biopsy showed patchy atrophy, necrosis, and increased interstitial connective tissue without any fibre enlargement.
He was started on thyroid hormone (Eltroxin) 0.1 mg per day and was followed up at monthly intervals. After six months of hormone replacement therapy his signs of hypothyroidism, associated myopathy, and hypertrophied calf muscles regressed. Repeat muscle biopsy revealed a decrease in interstitial connective tissue, atrophy, and necrosis with areas of muscle regeneration. Serum T3, T4, and TSH values also returned to normal.
Previous case reports of this variant of hypothyroid myopathy have described improvement of clinical features.3, 4 However, we found that maintenance of euthyroid state not only improved clinical features including the neurological manifestations of hypothyroidism, but also a marked regression of muscle enlargement. In our case we also demonstrated histological regression of changes in histopathology of hypertrophied muscle.