Introduction: Kocher-Debri-Semelaigne Syndrome(KDSS) is a rare disease associated with the association of muscular hypertrophy and prolonged, untreated moderate to severe hypothyroidism in the pediatric age group. It was first discovered by Theodor Kocher in 1892, but its association with pseudohypertrophy of muscle was emphasized by Robert Debri & George Semelaigne in 1935. The overall reported incidence of KDSS is less than 10% among hypothyroid cases. Identification is very important because hormone replacement therapy can fully reverse the clinical pictures, which can be potentially serious.

Case Report: We are reporting a 5-yr 9-month old female child of low socioeconomic background from a remote village of Bangladesh having H/O not achieved walking and speech, not growing well, and constipation since birth. She was diagnosed with Congenital Hypothyroidism at 2 years of ag,e which was grossly delayed with poor drug compliance. She was severely short-statured with infantile proportion body with coarse facies, depressed nasal bridge, dry texture of hair and skin, umbilical hernia with prominent muscular build at biceps and calf muscles. Her systemic examination revealed low intelligence quotient with psychomotor retardation, generalized hypotonia, and slow relaxation of the knee jerk. On investigations, there was primary hypothyroidism, delayed bone age <6 months & thyroid aplasia on USG ofthe gland. Creatinine Phosphokinase (CPK) was elevated, and the electromyogram revealed non-inflammatory myopathy. Treatment was started with Tab. Levothyroxine at low dose & gradually increased upto full dose to avoid side effects of sudden increase in metabolic rate due to thyroxin supplementation. Patient improved dramatically with drug adherence & regular follow-up. KDSS may be confused with primary muscular disorders. The striking clinical features, availability of simple treatment & good prognosis of the condition make it worthwhile to report the case so that all practitioners can be aware of the condition and its management.

Sultana Nadira Rahman is a pediatrician and pediatric endocrinologist currently serving as an Assistant Professor in the Department of Pediatric Endocrinology and Metabolic Disorders at Bangladesh Shishu Hospital & Institute, Dhaka. She completed her MBBS from Chittagong Medical College in 2005, obtained her Diploma in Child Health (DCH) in 2010 from the Bangladesh Institute of Child Health, and achieved FCPS in Pediatrics from the Bangladesh College of Physicians and Surgeons in January 2022. She has been working at Bangladesh Shishu Hospital & Institute since 2009, gaining extensive experience in pediatric clinical care, teaching, and hospital administration. She has received specialized training in dissertation guidance, IMCI, and management of severely malnourished children. Her research interests include pediatric endocrinology, metabolic disorders, pediatric meningitis, and rare endocrine syndromes, with multiple publications in national and international journals. She was awarded Best Presenter at the 4th International Conference of the Pediatric Endocrine Society of Bangladesh in December 2025.