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Paget's Disease of Bone

Paraganglioma

Paraneoplastic Neurologic Syndromes (PNS)

Paraneoplastic neurological syndromes (PNS) represent a group of rare, diverse conditions that affect the nervous system and are associated with cancer. These syndromes are not caused directly by the tumor itself but are thought to result from the body's immune response to the cancer. When the immune system attacks the cancer cells, it can mistakenly target healthy cells in the nervous system, leading to a variety of neurological symptoms. PNS can affect any part of the nervous system, including the brain, spinal cord, nerves, and muscles. The symptoms and severity of PNS vary widely among patients, depending on which part of the nervous system is affected. Common symptoms include difficulty with coordination, loss of muscle control, sensory changes, and cognitive dysfunction. Paraneoplastic opsoclonus/myoclonus syndrome and paraneoplastic cerebellar degeneration (PCD) are two specific types of PNS. Paraneoplastic opsoclonus/myoclonus syndrome is characterized by rapid, uncontrollable eye movements (opsoclonus) and brief, involuntary muscle jerks (myoclonus).

Parasitic Infections

Parasitic infections are caused by organisms that live on or within a host, deriving nutrients at the host’s expense. These organisms—classified broadly as protozoa, helminths (worms), and ectoparasites—can infect various parts of the body, including the gastrointestinal tract, blood, skin, and organs. Parasitic infections are more common in regions with limited sanitation and clean water access, but they can occur globally due to travel, food exposure, and environmental contact. Common parasitic infections include giardiasis, amoebiasis, malaria, toxoplasmosis, and intestinal worm infections such as roundworms, hookworms, and tapeworms. Transmission occurs through contaminated food or water, insect vectors (such as mosquitoes), soil exposure, or person-to-person contact, depending on the parasite. Symptoms vary widely based on the type of parasite, infection site, and host immune response. Gastrointestinal parasites may cause diarrhea, abdominal pain, bloating, nausea, and nutrient malabsorption.

PBC/Autoimmune Hepatitis Overlap Syndrome

Pericarditis

What Is Pericarditis? Pericarditis is inflammation of the pericardium, the thin, two-layered, fluid-filled sac that surrounds and protects the heart. Normally, a small amount of lubricating fluid sits between these layers, allowing the heart to move smoothly as it beats. When the pericardium becomes inflamed, the layers can rub against each other, causing chest pain and irritation around the heart. Types of Pericarditis Pericarditis is classified based on how long symptoms last: Acute pericarditis: sudden onset, lasting less than 3 weeks Subacute pericarditis: develops gradually, lasting 3 weeks to 3 months Chronic pericarditis: persists longer than 3 months Recurrent pericarditis: symptoms return after initial recovery It can affect people of any age but is most common in adults aged 20–50, with men affected more frequently than women.

Perimenopause

Perimenopause is the transitional phase leading up to menopause — the period during which the ovaries gradually reduce their production of estrogen and progesterone, ovulation becomes irregular, and the hormonal architecture of the reproductive years begins to shift. It is one of the most clinically significant and underrecognized hormonal transitions in women's health. The term means literally "around menopause." Unlike menopause itself — which is a specific event defined as 12 consecutive months without a period — perimenopause is a dynamic, multi-year process. It typically begins in a woman's mid-to-late 40s, though for some women it starts as early as the late 30s. Average duration is 4–8 years, though it can last as few as 1 year or as long as 10. Perimenopause ends and menopause begins with the final menstrual period — confirmed only in retrospect, once 12 months have passed without a period. A critical point that is frequently missed: perimenopause is not pre-menopause in the sense of being symptom-free.

Peripheral Neuropathy

Pernicious Anemia

Pharyngitis

Pheochromocytoma

Pneumonia

Polyclonal / Reactive Conditions

What Is Polyclonal Hypergammaglobulinemia? Polyclonal hypergammaglobulinemia refers to an increase in multiple different types of immunoglobulins (antibodies) in the blood. Unlike monoclonal conditions (such as MGUS or multiple myeloma), where a single abnormal protein is produced, polyclonal patterns reflect normal immune system activity responding to infection, inflammation, or other triggers. Key characteristics: Benign finding in most cases Multiple protein types elevated (not just one) Reflects active immune response Not associated with blood cancers Often improves when the underlying condition is treated Important: Polyclonal patterns are fundamentally different from monoclonal patterns and do not indicate plasma cell disorders like myeloma. Polyclonal vs.

Polycystic Kidney Disease

Polycystic ovary syndrome (PCOS)

Polycystic Ovary Syndrome (PCOS) Polycystic Ovary Syndrome (PCOS) is a common hormonal disorder affecting approximately 1 in 10 women of reproductive age. It is a complex condition with a wide range of symptoms that vary from person to person, primarily impacting reproductive health but also influencing metabolism and overall well-being. PCOS is characterized by hormonal imbalances that disrupt ovulation, often leading to irregular menstrual cycles, infertility, and the development of multiple small cysts on the ovaries, which may be detected via ultrasound. These hormonal disruptions are frequently associated with elevated androgen (male hormone) levels, contributing to symptoms such as acne, excessive hair growth (hirsutism), and scalp hair thinning. Additionally, PCOS is linked to metabolic concerns, including insulin resistance, an increased risk of type 2 diabetes, high cholesterol, hypertension, and heart disease. Diagnosis of PCOS Diagnosing PCOS can be challenging due to its diverse presentation and the absence of a single definitive test.

Polycythemia Vera

Polycythemia vera (PV) is a chronic myeloproliferative neoplasm in which the bone marrow produces too many red blood cells, and often excess white blood cells and platelets as well. It is caused by an acquired genetic mutation — most commonly JAK2 V617F, present in approximately 95% of cases — that drives uncontrolled blood cell production. PV is not inherited and is not a cancer in the conventional sense, though it carries a risk of progression to more serious conditions if untreated. The excess red blood cells thicken the blood, slowing circulation and increasing the risk of blood clots, which is the primary source of serious complications including stroke, deep vein thrombosis, and pulmonary embolism.

Polymyalgia rheumatica

Polymyositis

Post-Splenectomy State

Post-Surgical/Trauma Stress

Post-surgical and post-trauma stress refers to the body's physiological response to major physical injury or invasive surgical procedures, characterized by a coordinated cascade of metabolic, hormonal, and immune system changes aimed at promoting healing and survival. This stress response, also known as the surgical stress response or trauma response, is a normal and expected reaction that begins immediately after injury or surgery and typically lasts for several days to weeks depending on the severity of the insult. The body responds to surgical or traumatic injury through multiple interconnected pathways including activation of the hypothalamic-pituitary-adrenal axis leading to increased cortisol release, stimulation of the sympathetic nervous system causing elevated heart rate and blood pressure, release of inflammatory cytokines and acute-phase proteins, mobilization of energy stores through increased glucose production and protein breakdown, activation of the coagulation system to prevent excessive bleeding, and stimulation of bone marrow to produce increased numbers of white

Post-Transplant Immune Reconstitution

Post-Treatment Lyme Disease Syndrome

Postpartum Thyroiditis

Prader–Willi syndrome (PWS)

Precocious Puberty

Prediabetes

Preeclampsia

Pregnancy Complications

Pregnancy complications are medical conditions that arise during pregnancy and can affect the health of the mother, the developing baby, or both, ranging from mild issues that resolve with minimal intervention to serious conditions requiring immediate medical care. These complications can occur at any stage of pregnancy—during the first trimester, second trimester, third trimester, or during labor and delivery—and may develop suddenly or progress gradually over time. Common pregnancy complications include gestational diabetes (elevated blood sugar that develops during pregnancy), preeclampsia (high blood pressure with protein in the urine, typically occurring after 20 weeks of gestation), placenta previa (placenta covering the cervix), placental abruption (premature separation of the placenta from the uterine wall), preterm labor (labor beginning before 37 weeks), hyperemesis gravidarum (severe nausea and vomiting), infections such as urinary tract infections or chorioamnionitis (infection of the amniotic fluid and membranes), HELLP syndrome (a severe variant of preeclampsia

Premature Ovarian Insufficiency (POI)

Premature ovarian insufficiency (POI) is a condition in which the ovaries stop functioning normally before the age of 40. It is characterized by the loss of regular follicular activity, resulting in low estrogen production, elevated gonadotropins, and the cessation or irregularity of menstrual periods — often accompanied by infertility and symptoms similar to menopause. POI is distinct from natural menopause in several critical ways: it occurs decades earlier than expected, it carries significant long-term health consequences that are amplified by the extended duration of estrogen deficiency, it is frequently intermittent rather than permanent in its early stages, and in approximately 5–10% of affected women, spontaneous ovulation and even pregnancy can still occur after diagnosis. POI affects approximately 1 in 100 women by age 40, 1 in 1,000 by age 30, and 1 in 10,000 by age 20.

Prerenal Azotemia

Primary Biliary Cholangitis (PBC)

Primary Biliary Cholangitis (PBC): Overview and Management Primary Biliary Cholangitis (PBC) is a chronic, progressive autoimmune liver disease that leads to the gradual destruction of small bile ducts within the liver. It primarily affects women, with a female-to-male ratio of at least 9:1. Key Features of PBC Bile Duct Damage: PBC causes inflammation and scarring of the intrahepatic bile ducts, leading to bile buildup in the liver (cholestasis). Progression: Without treatment, PBC can lead to liver fibrosis, cirrhosis, and eventually liver failure. Prevalence: PBC is a relatively rare condition, affecting approximately 1 in 3,000 to 4,000 people. Symptoms of PBC Early Stages: Many individuals are asymptomatic at the time of diagnosis, with about 60% identified before symptoms appear.

Primary Myelofibrosis

Primary myelofibrosis (PMF) is a chronic myeloproliferative neoplasm in which the bone marrow becomes progressively replaced by fibrous scar tissue, disrupting its ability to produce blood cells normally. As the marrow fails, the spleen and liver take over blood cell production — a process called extramedullary hematopoiesis — leading to significant organ enlargement and a range of debilitating symptoms. PMF is driven by acquired genetic mutations, most commonly JAK2 V617F (present in approximately 50–60% of cases), CALR mutations (approximately 25%), or MPL mutations (approximately 5–10%). Around 10% of cases carry none of these three driver mutations (triple-negative PMF).

Prolactinoma

Propionic acidemia (PA)

Propionic aciduria

Prostate Cancer

Prostatitis

Proteinuria

Pseudogout

Psoriasis

Psoriasis is a chronic skin condition characterized by the rapid growth of skin cells, leading to thick, red, scaly patches on the skin. Normally, skin cells grow and shed over a period of weeks, but in psoriasis, this process is significantly accelerated, occurring over days. This results in the accumulation of skin cells on the surface, forming the distinctive plaques. Psoriasis is thought to be an autoimmune disorder, where the immune system mistakenly attacks healthy skin cells as if they were a threat, triggering this rapid turnover. The exact cause of psoriasis is not fully understood, but it is believed to involve a combination of genetic factors and environmental triggers. Triggers can vary from person to person and might include stress, skin injury (like cuts or scrapes), certain medications, or infections. Psoriasis is not contagious, meaning it cannot be spread from person to person. Symptoms of psoriasis can vary in severity and form.

Psoriatic Arthritis

Pulmonary arterial hypertension

Pulmonary Embolism

Pulmonary Hypertension