Okay, let's tackle this question. The patient is a 1-year-old with normal intelligence, hypotonia, tongue fasciculations, a frog-like posture, and loss of reflexes. Hmm, hypotonia in a child can be due to various causes. The key features here are the tongue fasciculations and the frog-like position. Frog-like posture makes me think of spinal muscular atrophy (SMA), specifically type 1, which is also called Werdnig-Hoffmann disease. But wait, SMA is an autosomal recessive disorder affecting motor neurons. The tongue fasciculations are a classic sign because of the loss of motor neurons in the brainstem. The frog-like position refers to the legs being flexed and abducted, which is common in SMA type 1. Also, the loss of reflexes is due to the absence of motor neuron activity. Let me check the other options. Maybe it's a different type of muscular dystrophy or a metabolic disorder. But the normal intelligence rules out some of those. Duchenne's is X-linked and usually has more muscle weakness and pseudohypertrophy. Mitochondrial disorders can cause hypotonia but often have other systemic issues. The key points here are the age, hypotonia, tongue fasciculations, and specific posture. So the most probable diagnosis is spinal muscular atrophy type 1.

**Core Concept**
This question tests recognition of **spinal muscular atrophy (SMA)**, a genetic motor neuron disease caused by mutations in the **SMN1 gene**. Key features include hypotonia, areflexia, and muscle atrophy, with preserved mental status.

**Why the Correct Answer is Right**
The clinical presentation of **hypotonia**, **tongue fasciculations**, **frog-like posture** (flexed legs, abducted thighs), and **loss of reflexes** is classic for **SMA type 1 (Werdnig-Hoffmann disease)**. SMA type 1 manifests in infancy (<6 months) with progressive motor weakness, atrophy, and loss of motor neurons in the anterior horn cells. Tongue fasciculations result from denervation of intrinsic tongue muscles. The frog-like posture reflects axial hypotonia and weakness of lower limb extensors. **Why Each Wrong Option is Incorrect** **Option A:** *Duchenne muscular dystrophy* presents with delayed motor milestones, pseudohypertrophy, and elevated CPK; hypotonia is less prominent. **Option B:** *Congenital myotonic dystrophy* includes myotonia, cataracts, and facial weakness, not typical SMA features. **Option C:** *Mitochondrial myopathy* may cause hypotonia but is associated with systemic symptoms (e.g., lactic acidosis, stroke-like episodes). **Clinical Pearl** SMA type 1 is a **pediatric emergency**—diagnose via **SMN1 gene deletion**. Early treatment with **nusinersen** or **onasemnogene abeparvovec** improves outcomes. Distinguish from muscular dystrophy by absence of elevated CPK and pseudohypertrophy. **Correct Answer: D. Spinal muscular atrophy (Werdnig-Hoffmann disease)**

✓ Correct Answer: D. Spinal muscular atrophy