Porphyrias

Definition and Epidemiology

Definition

Porphyrias are rare metabolic disorders caused by impairments in heme synthesis Synthesis Polymerase Chain Reaction (PCR).

• Characterized by a buildup of substances called porphyrins
• Types of porphyria are differentiated by the type of porphyrin that accumulates in the blood, urine, or stool.
• May affect the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions, liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy, and nervous system Nervous system The nervous system is a small and complex system that consists of an intricate network of neural cells (or neurons) and even more glial cells (for support and insulation). It is divided according to its anatomical components as well as its functional characteristics. The brain and spinal cord are referred to as the central nervous system, and the branches of nerves from these structures are referred to as the peripheral nervous system. Nervous System: Anatomy, Structure, and Classification

Epidemiology

• Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: approximately 5 cases per 100,000 population
• Most common type is porphyria cutanea tarda ( PCT PCT The renal tubule portion that extends from the bowman capsule in the kidney cortex into the kidney medulla. The proximal tubule consists of a convoluted proximal segment in the cortex, and a distal straight segment descending into the medulla where it forms the u-shaped loop of henle. Osmotic Diuretics).
• 2nd most common type is acute intermittent porphyria.

Pathophysiology

Porphyrias are due to enzymatic defects in heme biosynthesis Biosynthesis The biosynthesis of peptides and proteins on ribosomes, directed by messenger RNA, via transfer RNA that is charged with standard proteinogenic amino acids. Virology:

• Heme is produced in the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy and bone marrow Bone marrow The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells. Bone Marrow: Composition and Hematopoiesis.
• Involves 8 enzymatic steps, starting with glycine Glycine A non-essential amino acid. It is found primarily in gelatin and silk fibroin and used therapeutically as a nutrient. It is also a fast inhibitory neurotransmitter. Synthesis of Nonessential Amino Acids
• Enzyme absence or dysfunction leads to buildup of heme precursors.
• Excess precursors accumulate in tissues, leading to clinical symptoms.

Most commonly, porphyrias are due to an inherited enzyme defect within the heme biosynthesis Biosynthesis The biosynthesis of peptides and proteins on ribosomes, directed by messenger RNA, via transfer RNA that is charged with standard proteinogenic amino acids. Virology pathway. They may rarely be acquired later in life:

• Alcohol use disorder Alcohol use disorder Alcohol is one of the most commonly used addictive substances in the world. Alcohol use disorder (AUD) is defined as pathologic consumption of alcohol leading to impaired daily functioning. Acute alcohol intoxication presents with impairment in speech and motor functions and can be managed in most cases with supportive care. Alcohol Use Disorder
• Infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease (e.g., hepatitis C Hepatitis C Hepatitis C is an infection of the liver caused by the hepatitis C virus (HCV). The infection can be transmitted through infectious blood or body fluids and may be transmitted during childbirth or through IV drug use or sexual intercourse. Hepatitis C virus can cause both acute and chronic hepatitis, ranging from a mild to a serious, lifelong illness including liver cirrhosis and hepatocellular carcinoma (HCC). Hepatitis C Virus and HIV HIV Anti-HIV Drugs/ AIDS AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS)
• Increased estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy levels

Clinical Presentation

Clinical presentation depends on the pattern of organ involvement.

• Chronic porphyria → increased skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions manifestations (e.g., blisters and erosions Erosions Corneal Abrasions, Erosion, and Ulcers)
• Acute porphyria → systemic findings (e.g., abdominal pain Abdominal Pain Acute Abdomen, liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy enzyme elevation)
• Most common forms:
  • Porphyria cutanea tarda
  • Acute intermittent porphyria 
  • Erythropoietic protoporphyria:
    • Congenital Congenital Chorioretinitis erythropoietic porphyria ( autosomal recessive Autosomal recessive Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal recessive diseases are only expressed when 2 copies of the recessive allele are inherited. Autosomal Recessive and Autosomal Dominant Inheritance)
    • Erythropoietic protoporphyria ( autosomal dominant Autosomal dominant Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal dominant diseases are expressed when only 1 copy of the dominant allele is inherited. Autosomal Recessive and Autosomal Dominant Inheritance)

Porphyria cutanea tarda

• Most common porphyria
• Caused by defect in uroporphyrinogen III decarboxylase
• Can be inherited in an autosomal dominant Autosomal dominant Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal dominant diseases are expressed when only 1 copy of the dominant allele is inherited. Autosomal Recessive and Autosomal Dominant Inheritance manner or acquired later in life
• Acquired PCT PCT The renal tubule portion that extends from the bowman capsule in the kidney cortex into the kidney medulla. The proximal tubule consists of a convoluted proximal segment in the cortex, and a distal straight segment descending into the medulla where it forms the u-shaped loop of henle. Osmotic Diuretics can be triggered by:
  • Alcohol use disorder Alcohol use disorder Alcohol is one of the most commonly used addictive substances in the world. Alcohol use disorder (AUD) is defined as pathologic consumption of alcohol leading to impaired daily functioning. Acute alcohol intoxication presents with impairment in speech and motor functions and can be managed in most cases with supportive care. Alcohol Use Disorder
  • Exogenous estrogens
  • Infection (often hepatitis C Hepatitis C Hepatitis C is an infection of the liver caused by the hepatitis C virus (HCV). The infection can be transmitted through infectious blood or body fluids and may be transmitted during childbirth or through IV drug use or sexual intercourse. Hepatitis C virus can cause both acute and chronic hepatitis, ranging from a mild to a serious, lifelong illness including liver cirrhosis and hepatocellular carcinoma (HCC). Hepatitis C Virus)
• Leads to buildup of uroporphyrinogen III
• Symptoms include:
  • Photosensitivity Photosensitivity Tetracyclines of skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions
  • Blistering skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions lesions
  • Scars on face and back of hands
  • Hypertrichosis
  • Hyperpigmentation Hyperpigmentation Excessive pigmentation of the skin, usually as a result of increased epidermal or dermal melanin pigmentation, hypermelanosis. Hyperpigmentation can be localized or generalized. The condition may arise from exposure to light, chemicals or other substances, or from a primary metabolic imbalance. Malassezia Fungi
• Porphyrin deposits cause progressive liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy damage:
  • Elevated liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy function enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes
  • Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy nodules can be detected on ultrasound.
• Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship will have dark-colored urine due to elevated uroporphyrins.

Acute intermittent porphyria

• 2nd most common porphyria
• Peak incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: 3rd decade of life
• Porphobilinogen Porphobilinogen Heme Metabolism deaminase is the affected enzyme. Increase in preceding intermediates in metabolic pathway:
  • Porphobilinogen Porphobilinogen Heme Metabolism ( PBG PBG Heme Metabolism)
  • δ-Aminolevulinic acid (ALA)
• Symptoms include:
  • Colicky abdominal pain Abdominal Pain Acute Abdomen
  • Neurologic abnormalities
  • Disorientation Disorientation St. Louis Encephalitis Virus

Congenital Congenital Chorioretinitis erythropoietic porphyria

• Caused by defect in uroporphyrinogen III synthase Uroporphyrinogen III synthase An enzyme that catalyzes the cyclization of hydroxymethylbilane to yield uroporphyrinogen III and water. It is the fourth enzyme in the 8-enzyme biosynthetic pathway of heme, and is encoded by uros gene. Heme Metabolism
• Symptoms include:
  • Skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions photosensitivity Photosensitivity Tetracyclines: blister Blister Bullous Pemphigoid and Pemphigus Vulgaris formation
  • Erythrodontia (red teeth Teeth Normally, an adult has 32 teeth: 16 maxillary and 16 mandibular. These teeth are divided into 4 quadrants with 8 teeth each. Each quadrant consists of 2 incisors (dentes incisivi), 1 canine (dens caninus), 2 premolars (dentes premolares), and 3 molars (dentes molares). Teeth are composed of enamel, dentin, and dental cement. Teeth: Anatomy)
  • Colicky abdominal pain Abdominal Pain Acute Abdomen

Diagnosis

The diagnosis of porphyrias is typically made using specialized blood tests.

• If suspected, can screen with urine and blood tests:
  • Urine would have elevated PBG PBG Heme Metabolism levels.
    • PBG PBG Heme Metabolism is 1 of the 1st substances in the porphyrin synthesis Synthesis Polymerase Chain Reaction (PCR) pathway.
    • Other urinary porphyrins may also be elevated.
  • Serum porphyrins will be elevated.
• Discolored urine when left standing (yellow to dark red)
• PBG PBG Heme Metabolism also detected in stool
• To confirm diagnosis, test for function of suspected enzyme defect.

Management

There is no known cure for porphyria.

• Prevent flares with strict avoidance of triggers (e.g., alcohol, sunlight).
• Symptomatic treatment when flares occur:
  • Phlebotomy Phlebotomy The techniques used to draw blood from a vein for diagnostic purposes or for treatment of certain blood disorders such as erythrocytosis, hemochromatosis, polycythemia vera, and porphyria cutanea tarda. Hereditary Hemochromatosis to remove porphyrins
  • Pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways management → NSAIDs NSAIDS Primary vs Secondary Headaches, opioids Opioids Opiates are drugs that are derived from the sap of the opium poppy. Opiates have been used since antiquity for the relief of acute severe pain. Opioids are synthetic opiates with properties that are substantially similar to those of opiates. Opioid Analgesics
  • Vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia → antiemetics Antiemetics Antiemetics are medications used to treat and/or prevent nausea and vomiting. These drugs act on different target receptors. The main classes include benzodiazepines, corticosteroids, atypical antipsychotics, cannabinoids, and antagonists of the following receptors: serotonin, dopamine, and muscarinic and neurokinin receptors. Antiemetics
  • Tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children → beta-blockers Beta-blockers Drugs that bind to but do not activate beta-adrenergic receptors thereby blocking the actions of beta-adrenergic agonists. Adrenergic beta-antagonists are used for treatment of hypertension, cardiac arrhythmias, angina pectoris, glaucoma, migraine headaches, and anxiety. Class 2 Antiarrhythmic Drugs (Beta Blockers)
  • Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures → antiepileptics
• Acute attack: IV hemin → decreases heme biosynthesis Biosynthesis The biosynthesis of peptides and proteins on ribosomes, directed by messenger RNA, via transfer RNA that is charged with standard proteinogenic amino acids. Virology

Differential Diagnosis

• Lead poisoning Lead poisoning Poisoning that results from chronic or acute ingestion, injection, inhalation, or skin absorption of lead or lead compounds. Metal Poisoning (Lead, Arsenic, Iron): leads to decreased hemoglobin synthesis Synthesis Polymerase Chain Reaction (PCR). Symptoms of lead poisoning Lead poisoning Poisoning that results from chronic or acute ingestion, injection, inhalation, or skin absorption of lead or lead compounds. Metal Poisoning (Lead, Arsenic, Iron) include nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics, vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia, headaches, encephalopathy Encephalopathy Hyper-IgM Syndrome, and peripheral neuropathy Neuropathy Leprosy. Treatment is aimed at decreasing lead levels with chelation.
• Acute anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types: condition in which individuals have low hemoglobin levels. Symptoms include fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia, shortness of breath Shortness of breath Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea, pallor, and weakness. Anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types may occur because of blood loss, decreased RBC production such as in iron Iron A metallic element with atomic symbol fe, atomic number 26, and atomic weight 55. 85. It is an essential constituent of hemoglobins; cytochromes; and iron-binding proteins. It plays a role in cellular redox reactions and in the transport of oxygen. Trace Elements deficiency, or increased RBC destruction such as in hemolysis. Management is aimed at improving hemoglobin levels and treating the underlying conditions.
• Hepatitis B Hepatitis B Hepatitis B virus (HBV) is a partially double-stranded DNA virus, which belongs to the Orthohepadnavirus genus and the Hepadnaviridae family. Most individuals with acute HBV infection are asymptomatic or have mild, self-limiting symptoms. Chronic infection can be asymptomatic or create hepatic inflammation, leading to liver cirrhosis and hepatocellular carcinoma (HCC). Hepatitis B Virus and C: viral infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease of the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy that cause inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and damage of hepatocytes Hepatocytes The main structural component of the liver. They are specialized epithelial cells that are organized into interconnected plates called lobules. Liver: Anatomy. The presentation of these 2 infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease depends on whether the infection is acute or chronic, and it is specific to the type of hepatitis present. Diagnosis is established by detecting antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions or viral antigens in the serum. 
• Hodgkin lymphoma Lymphoma A general term for various neoplastic diseases of the lymphoid tissue. Imaging of the Mediastinum: malignancy Malignancy Hemothorax of B lymphocytes B lymphocytes Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation. B cells: Types and Functions originating in lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy. The disease presents most commonly with lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy ( neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess most commonly involved), night sweats Night sweats Tuberculosis, weight loss Weight loss Decrease in existing body weight. Bariatric Surgery, fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, and at times, splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly and hepatomegaly. Hodgkin lymphoma Lymphoma A general term for various neoplastic diseases of the lymphoid tissue. Imaging of the Mediastinum is managed with chemotherapy Chemotherapy Osteosarcoma and radiotherapy.
• Acute lymphoblastic leukemia Acute Lymphoblastic Leukemia Acute lymphoblastic leukemia/lymphoma (ALL/LBL) are hematologic malignancies characterized by the uncontrolled proliferation of lymphoid precursor cells. Acute lymphoblastic leukemia/lymphoma, the most common forms of cancer affecting children, show the presence of increased lymphoblasts. Acute Lymphoblastic Leukemia (ALL): hematologic malignancy Malignancy Hemothorax that starts in the bone marrow Bone marrow The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells. Bone Marrow: Composition and Hematopoiesis. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship present with fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia, pallor, bleeding, fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, and infection related to the anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types, thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia, and lack of functional WBCs seen in acute leukemia. Diagnosis is made with peripheral blood smear Peripheral Blood Smear Anemia: Overview and Types and bone marrow Bone marrow The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells. Bone Marrow: Composition and Hematopoiesis biopsy Biopsy Removal and pathologic examination of specimens from the living body. Ewing Sarcoma findings.