**Question:** In which of the following pervasive developmental disorder only one modality is impaired, others are normal -

A. Autism Spectrum Disorder (ASD)
B. Attention Deficit Hyperactivity Disorder (ADHD)
C. Dyslexia
D. Dyspraxia

**Correct Answer:** .

**Core Concept:**
Pervasive developmental disorders (PDDs) are a group of neurodevelopmental disorders characterized by impairments in social interaction, communication, and imaginative play or social skills. They are typically diagnosed in early childhood and are part of the broader category of Autism Spectrum Disorders (ASDs). These disorders encompass a range of conditions, including autism, Asperger's syndrome, and pervasive developmental disorder not otherwise specified (PDD-NOS).

**Why the Correct Answer is Right:**
The correct answer, Dyspraxia, is a motor planning disorder characterized by difficulty with motor coordination, balance, and muscle tone control. While it shares some clinical features with ASD, it primarily affects motor functions and does not encompass impairments in social interaction, communication, and imagination. In contrast, other options like ASD, ADHD, and Dyslexia involve impairments in multiple domains (social interaction, communication, and other cognitive functions) and are not limited to a single modality.

**Why Each Wrong Option is Incorrect:**

A. Autism Spectrum Disorder (ASD) - ASD is a neurodevelopmental disorder affecting social interaction, communication, and imagination. Impairments in multiple modalities (e.g., social, communication, and imagination) make it distinct from the correct answer Dyspraxia.

B. Attention Deficit Hyperactivity Disorder (ADHD) - ADHD is a neurodevelopmental disorder characterized by inattention, hyperactivity, and impulsivity. It affects multiple modalities (e.g., attention, hyperactivity, and impulsivity) and is distinct from Dyspraxia.

C. Dyslexia - Dyslexia is a reading disorder affecting language-based skills such as reading, writing, and spelling. It involves multiple modalities (e.g., language processing and literacy) and is different from Dyspraxia.

**Clinical Pearls:**
Dyspraxia, also known as Developmental Coordination Disorder (DCD), is a neurodevelopmental disorder characterized by difficulties in motor planning and coordination. It primarily affects motor functions, including balance, muscle tone control, and coordination. The disorder is usually diagnosed in childhood and can impact daily activities, academic performance, and social interactions.

Dyspraxia is a distinct condition from ASD, ADHD, and dyslexia, which involve impairments in multiple modalities (e.g., social interaction, attention, and language processing). Dyspraxia specifically targets motor skills and coordination, making it a unique clinical entity when compared to the other options.

**Core Concepts:**
1. Dyspraxia is a motor planning disorder affecting motor functions, while ASD, ADHD, and dyslexia involve impairments in multiple domains like social interaction, attention,