Step 1: Understanding the Concept
Low BMR, thick tongue, prolonged neonatal jaundice, lethargy and constipation indicate deficiency of thyroid hormone from birth.
Step 2: Compare
Myxoedema is hypothyroidism in adults. Cushing's disease and Addison's disease involve adrenal hormones.
Hypothyroidism in children is called cretinism.
Step 3: Match
The disease is cretinism, option (D).
Final Answer:
The child has cretinism.
\[ \boxed{\text{(D) }\text{Cretinism}} \]