Atrophy refers to the shrinkage or wasting away of a tissue or organ due to a reduction in the size or number of its cells. It can affect muscles, organs, or other tissues and may result in functional impairment depending on severity and location.

Pathophysiology

Atrophy occurs when cellular protein synthesis decreases or degradation increases, leading to reduced cell size or cell loss. Mechanisms include:

• Disuse: Reduced workload or immobilization leads to skeletal muscle atrophy.

• Denervation: Loss of neural input reduces trophic support to muscles.

• Ischemia: Reduced blood supply impairs nutrient delivery, causing tissue loss.

• Endocrine changes: Hormonal deficiencies (e.g., estrogen in ovaries, thyroid in thyroid atrophy) lead to cell shrinkage.

• Nutritional deficiencies: Inadequate proteins or calories impair tissue maintenance.

• Aging (physiologic atrophy): Normal reduction in organ size or function over time, such as brain and skin atrophy.

• Pathologic causes: Chronic disease, inflammatory conditions, or metabolic disorders can lead to tissue-specific atrophy (e.g., liver, spleen, or neurologic tissue).

Examination Technique

• Inspection: Observe for decreased muscle mass, reduced organ size, or skin thinning. Look for asymmetry or changes compared to the contralateral side.

• Palpation: Assess texture, firmness, and bulk of muscles or superficial organs. Soft, flaccid tissues may indicate atrophy.

• Functional assessment: Evaluate strength, range of motion, and performance in daily activities.

• Imaging: Ultrasound, CT, or MRI can quantify organ or muscle atrophy when clinical evaluation is insufficient.

Clinical Utility

• Early detection: Identifying atrophy can reveal underlying neurologic, metabolic, or endocrine disorders.

• Monitoring disease progression: Repeated assessments track progression in chronic diseases such as muscular dystrophy or liver cirrhosis.

• Therapeutic guidance: Determines need for physiotherapy, nutritional supplementation, or surgical intervention.

Differential Diagnosis

History and Physical Examination

• History: Ask about duration, progression, recent illness, immobilization, neurologic deficits, or systemic disorders.

• Physical Examination: Compare bilateral symmetry, palpate for tissue bulk, assess muscle strength and reflexes. Document organ size changes if palpable (e.g., thyroid, liver, spleen).

Diagnostic approach

• Laboratory tests: Evaluate endocrine, nutritional, or metabolic causes (thyroid function, cortisol, protein levels).

• Imaging: MRI, CT, or ultrasound to assess internal organ atrophy or muscle wasting.

• Electromyography (EMG): Assesses denervation-induced atrophy in muscles.

• Biopsy (rarely): Confirms cellular loss and distinguishes atrophy from other degenerative processes.

Management

• Address underlying cause: Correct endocrine deficiencies, nutritional deficits, or neurologic disorders.

• Physical therapy: Strengthening exercises to prevent further muscle loss and improve function.

• Occupational therapy: Adaptation for daily activities when functional impairment occurs.

• Pharmacologic interventions: Hormone replacement, anti-inflammatory agents, or disease-specific treatments as indicated.

• Lifestyle modification: Adequate nutrition, exercise, and avoidance of immobilization.

Patient counseling

• Explain that atrophy may be physiologic or pathologic, depending on the underlying cause.

• Emphasize adherence to therapy, nutrition, and exercise to slow progression.

• Discuss regular follow-up for monitoring and early detection of complications.

Pediatric considerations

• Growth delays or muscle wasting may indicate congenital disorders, malnutrition, or chronic illness.

• Early intervention with nutrition and physical therapy is critical for normal development.

Geriatric considerations

• Age-related atrophy is common and may affect muscle mass, brain volume, and skin elasticity.

• Focus on maintaining mobility, strength, and independence through exercise and nutrition.

Key points

• Atrophy is characterized by reduction in tissue or organ size due to cellular shrinkage or loss.

• It can be physiologic (aging) or pathologic (neurologic, endocrine, chronic disease).

• Early recognition allows targeted therapy and helps maintain function.

References

1. Buttaro TM, Tybulski J, Bailey PP, Sandberg-Cook J. Primary Care: A Collaborative Practice. St. Louis, MO: Mosby Elsevier; 2008. p. 444–447.

2. McCance KL, Huether SE, Brashers VL, Rote NS. Pathophysiology: The Biologic Basis for Disease in Adults and Children. 8th ed. Maryland Heights, MO: Mosby Elsevier; 2019.

3. Hall JE. Guyton and Hall Textbook of Medical Physiology. 14th ed. Philadelphia, PA: Elsevier; 2021.

4. Narici MV, Maffulli N. Sarcopenia: Characteristics, Mechanisms and Functional Significance. Br Med Bull. 2010;95:139–159.

5. Campbell WW. Evaluation and Management of Muscle Wasting. N Engl J Med. 2016;374:1458–1467.