A medical doctor who specialises in diagnosing and treating diseases and disorders of the skin is called by which professional title?

Introduction / Context:
Modern medicine has many specialist doctors, each focusing on a particular organ system or type of disease. Knowing the correct titles of these specialists is useful in everyday life and is often tested in general knowledge and basic science exams. Skin problems are very common, and there is a specific type of doctor who deals with skin, hair, and nail disorders. This question asks for the name of that specialist.

Given Data / Assumptions:
- The question refers to a doctor specialising in skin diseases.
- Options include nephrologist, dermatologist, pediatrician, and rheumatologist.
- We assume standard medical specialisation names.
- The focus is on identifying the correct match between organ system and doctor title.

Concept / Approach:
A dermatologist is a medical doctor who specialises in dermatology, the branch of medicine dealing with the skin, hair, nails, and related diseases. Nephrologists specialise in kidney diseases, pediatricians focus on the health of children, and rheumatologists deal with joint, autoimmune, and connective tissue disorders. Since the question specifically mentions skin diseases, dermatologist is the correct professional title.

Step-by-Step Solution:
Step 1: Link the word derma with skin, as in the outer covering of the body. Step 2: Recall that dermatology is the medical field that studies skin and its diseases. Step 3: Recognise that a dermatologist is the doctor who practises dermatology. Step 4: Compare this with nephrologist for kidneys, pediatrician for children, and rheumatologist for joints and autoimmune conditions. Step 5: Select dermatologist as the correct answer.

Verification / Alternative check:
Hospitals and clinics typically have dermatology departments or skin clinics run by dermatologists. Medical directories list dermatologists as specialists for acne, eczema, psoriasis, infections, and other skin conditions. In contrast, nephrologists appear in kidney clinics, pediatricians in child health clinics, and rheumatologists in rheumatology services. This clear division of specialties confirms that dermatologist is the correct term for a skin specialist.

Why Other Options Are Wrong:
- Nephrologist specialises in diseases of the kidneys and related disorders of fluid and electrolyte balance.
- Pediatrician focuses on the medical care of infants, children, and adolescents, not specifically on skin diseases.
- Rheumatologist deals with arthritis, autoimmune diseases, and connective tissue disorders, which may involve joints and other organs rather than focusing only on the skin.

Common Pitfalls:
Learners sometimes confuse similar sounding medical terms or forget the root meanings of words. Remembering that derma refers to skin, nephro to kidney, ped to child, and rheuma to flow or joint related pain can help match each speciality with its area of focus. When a question directly mentions skin diseases, dermatologist should immediately come to mind as the correct specialist.

Final Answer:
A doctor who specialises in skin diseases is called a Dermatologist.