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Give me the types and causes of PCM in biochemistry

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"protein-energy malnutrition"[MeSH Terms]

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WHO protein-energy malnutrition causes marasmus kwashiorkor

Protein-calorie malnutrition (PCM), also called protein-energy malnutrition (PEM), results from deficiency of dietary energy, protein, or both.

Types of PCM

  1. Marasmus
    • Caused mainly by severe deficiency of total calories/energy, with protein deficiency also present.
    • Features: marked wasting of skeletal muscle and subcutaneous fat, severe weight loss, stunted growth, “old-man” appearance.
    • Edema is absent.
  2. Kwashiorkor
    • Classically associated with severe protein deficiency, often when calorie intake is relatively better due to a carbohydrate-rich diet.
    • Features: edema, fatty liver, muscle wasting, growth failure, sparse/discolored hair, flaky-paint dermatosis, irritability, and low serum albumin.
    • Edema results largely from reduced visceral protein synthesis and hypoalbuminemia. Robbins describes severe visceral protein loss and hypoalbuminemia as a distinguishing feature. StatPearls review discusses the clinical distinction.
  3. Marasmic kwashiorkor
    • A mixed form with features of both conditions.
    • Severe wasting as in marasmus plus edema as in kwashiorkor.

Causes of PCM

Primary causes

Due directly to inadequate food intake:
  • Poverty and food insecurity
  • Inadequate breastfeeding or improper complementary feeding
  • Early weaning onto carbohydrate-rich, protein-poor foods
  • Famine, drought, war, displacement, and neglect
  • Poor nutrition education
  • Large family size and inadequate child care
  • Diet lacking essential amino acids and sufficient calories

Secondary causes

Food may be available, but intake, digestion, absorption, utilization, or requirements are impaired:
  • Malabsorption disorders: celiac disease, chronic diarrhea, inflammatory bowel disease, pancreatic insufficiency
  • Chronic infections: tuberculosis, HIV, recurrent diarrhea, parasitic infestations
  • Increased metabolic requirements: burns, trauma, surgery, cancer, chronic inflammation
  • Chronic organ disease: heart failure, chronic kidney disease, liver disease
  • Poor intake: anorexia, alcoholism, depression, swallowing difficulty, persistent vomiting
  • Excessive nutrient loss: intestinal fistulae, severe diarrhea, protein-losing enteropathy, nephrotic syndrome
Exam summary:
  • Marasmus: deficiency of calories and protein, predominant energy deficiency, no edema.
  • Kwashiorkor: predominant protein deficiency, edema and fatty liver.
  • Marasmic kwashiorkor: wasting with edema.
Although this classic distinction is useful for exams, kwashiorkor is now understood to be multifactorial, with infection, micronutrient deficiency, oxidative stress, gut dysfunction, and environmental exposures potentially contributing alongside dietary protein deficiency.

Are there five types?

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"protein-energy malnutrition"[MeSH Terms]

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protein energy malnutrition five types marasmus kwashiorkor underweight stunting wasting

Not in the usual clinical classification of PCM.
There are generally 3 types:
  1. Marasmus - severe calorie and protein deficiency; marked wasting; no edema.
  2. Kwashiorkor - predominant protein deficiency; edema, fatty liver, hair and skin changes.
  3. Marasmic kwashiorkor - mixed form; severe wasting with edema.
You may see five terms in some community medicine or nutrition notes:
  1. Underweight
  2. Stunting
  3. Wasting
  4. Marasmus
  5. Kwashiorkor
But underweight, stunting, and wasting are anthropometric indicators or manifestations of undernutrition, not separate clinical types of PCM. A standard pathology description recognizes kwashiorkor and marasmus as the key forms, with a mixed marasmic-kwashiorkor form.
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