What is polyarteritis nodosa? morphology and clinical features?

 Polyarteritis Nodosa

Polyarteritis nodosa (PAN) is a systemic vasculitis of small- or medium-sized muscular arteries; it typically involves the renal and visceral vessels and spares the pulmonary circulation. There is no association with ANCAS, but one-third of patients have chronic hepatitis B infection, which leads to the formation of immune complexes containing hepatitis B antigens that deposit in affected vessels. The cause is unknown in the remaining cases.

Pathogenesis of PAN

  • Immune complex–mediated vasculitis, often linked to Hepatitis B.

  • Immune complexes deposit in medium-sized arteries.

  • Activate the complement system → recruit neutrophils.

  • Causes fibrinoid necrosis and inflammation of the vessel wall.

  • Leads to thrombosis, aneurysms, and organ ischemia.

  • Not associated with ANCA.

Morphology of PAN

Classic PAN is a segmental transmural necrotizing inflammation of small- to medium-sized arteries, often with superimposed thrombosis. Kidney, heart, liver, and gastrointestinal tract vessels are affected in descending order of frequency. Lesions usually involve only part of the vessel circumference and have a predilection for branch points. Impaired perfusion may lead to ulcerations, infarcts, ischemic atrophy, or hemorrhages in the distribution of affected vessels. The inflammatory process also weakens the arterial wall, leading to aneurysms and rupture.

What is polyarteritis nodosa?


In the acute phase, there is transmural mixed inflammatory infiltrate composed of neutrophils and mononuclear cells, frequently accompanied by fibrinoid necrosis and luminal thrombosis. Older lesions show fibrous thickening of the vessel wall extending into the adventitia. Characteristically, all stages of activity (from early to late) coexist in different vessels or even within the same vessel, suggesting ongoing and recurrent pathogenic insults.

Clinical Features

PAN is primarily a disease of young adults but can occur in all age groups. The clinical course typically is episodic, with long symptom-free intervals:

  • Systemic symptoms: Fever, weight loss, and fatigue.

  • Renal: Hypertension, hematuria (no glomerulonephritis).

  • Gastrointestinal: Abdominal pain, bleeding, infarction.

  • Musculoskeletal: Myalgia, arthralgia.

  • Neurological: Mononeuritis multiplex (asymmetric neuropathy).

  • Skin: Livedo reticularis, nodules, ulcers, purpura.

  • Cardiac: Myocardial ischemia (due to coronary vasculitis).

Untreated, PAN typically is fatal; however, with immunosuppression, 5-year survival is close to 80%. Relapse occurs in up to 25% of the cases, more often in non-HBV-associated cases than those that follow HBV infection. The latter have a better long-term prognosis.

Comments

Post a Comment

Popular posts from this blog

What is a dpt program?

 🩺 What is the DPT Program?  If you've ever been fascinated by how the human body moves and heals — and want a career that blends science, care, and impact — then a  Doctor of Physical Therapy (DPT)  program might be your perfect match. Whether you're a high school student exploring health careers, a college graduate looking to specialize, or just curious about physical therapy education, this article will break down  what the DPT program is , what it includes, and how it prepares you to become a licensed physical therapist. 🧠 What is a DPT Program? The  Doctor of Physical Therapy (DPT)  program is a  postgraduate professional doctorate  designed to train students to become licensed  physical therapists (PTs) . It’s the  entry-level requirement  for anyone who wants to practice as a PT in many countries, including the United States. This degree focuses on: Movement science Patient rehabilitation Injury prevention Manual thera...
Read more

What is osteogenesis imperfecta?

Image
What is Osteogenesis Imperfecta? | Causes, Types, Symptoms & Treatment Osteogenesis Imperfecta (OI) , also known as “brittle bone disease,” is a rare genetic disorder characterized by fragile bones that break easily , often with little or no trauma. It affects the production of collagen , a key protein that provides strength and structure to bones and connective tissues.  What is Osteogenesis Imperfecta? Osteogenesis Imperfecta is a hereditary connective tissue disorder . It primarily affects the bones but may also involve the teeth, skin, ligaments, and eyes . The condition is caused by mutations in genes—mostly COL1A1 or COL1A2 —that control the production of type I collagen . As a result, bones become brittle, leading to frequent fractures and skeletal deformities.  Types of Osteogenesis Imperfecta  There are at least eight recognized types of OI, varying from mild to severe. Here's a simplified breakdown: Type Description Severity Type I Most...
Read more

what is brain encephalitis?

Image
Brain Encephalitis: Causes, Symptoms, Diagnosis & Treatment Encephalitis is a serious and potentially life-threatening medical condition characterized by inflammation of the brain . It is often caused by a viral infection  but may also occur due to autoimmune reactions, bacteria, or other pathogens. If not treated promptly, encephalitis can lead to severe neurological complications.  What is Brain Encephalitis? Encephalitis is the inflammation of brain tissue. The inflammation causes the brain to swell, which can interfere with normal brain function and lead to a wide range of neurological symptoms. It can be classified as: Primary encephalitis : Direct viral infection of the brain. Secondary encephalitis : An immune response following an infection elsewhere in the body. Causes of Encephalitis 1. Viral Infections (Most Common Cause) Herpes Simplex Virus (most common and severe) Enteroviruses Varicella-zoster virus (chickenpox) Measles, mumps, r...
Read more