Duchenne muscular dystrophy with Kocher-Debre-Semelaigne syndrome: a double jeopardy

Duchenne muscular dystrophy (DMD) is a progressive X-linked dystrophinopathy with onset in early childhood. Affected individuals present predominantly with proximal lower limb weakness and pseudohypertrophy of calf musculature being a prominent sign, heralding the onset of contractures in the large joints of lower limbs. Kocher-Debre-Semelaigne syndrome (KDSS) refers to the muscular pseudohypertrophy that develops in children with long-standing hypothyroidism.

We present an 11-year-old boy with progressive walking difficulty for two years and associated decrease in appetite and chronic constipation. Physical examination revealed mild soft goitre, proximal lower limb weakness, areflexia (except for preserved weak ankle reflex), soft hypertrophy of bilateral calf muscles and latissimus dorsi, with bilateral dynamic ankle joint contractures. Investigations showed moderately elevated total serum creatine phosphokinase (CPK) levels, elevated serum thyroid stimulating hormone (TSH), low free T4, normal free T3 and elevated serum anti-thyroid peroxidase and anti-thyroglobulin antibody titers. A diagnosis of hypothyroidism secondary to Hashimoto's thyroiditis with Kocher-Debre-Semelaigne syndrome (KDSS) (thyroid myopathy) was made while multiplex ligation-dependent probe amplification confirmed DMD. He was started on steroids and levothyroxine. On follow up, he had improvement in activity, appetite and motor movements (North Star Ambulatory Assessment score 3 to 7).

As a very rare coincidence, our patient suffered from two different diseases with similar presentation which are DMD and KDSS. Subtle clinical clues of joint contractures and goitre helped us identify these unrelated co-existing diseases. An alternate diagnosis must be thought of when all clinical findings cannot be explained by a single disease.