- C1 esterase deficiency
- Café au lait spots
- Caffeine
- Caffeine toxicity
- Caffeine withdrawal
- Caffey disease
- Caisson disease
- Calcaneovalgus
- Calcinosis
- Calcium channel blockers
- Calcium imbalance
- Calcium supplementation
- Calculi
- California (LaCrosse) encephalitis
- Campbell-Williams syndrome
- Campomelic dysplasia
- Campylobacter infections
- Canavan disease
- Cancer
- Candidal dermatitis
- Candidal nipple infection
- Candidemia
- Candidiasis
- Capillary malformations
- Carbonic anhydrase inhibitors
- Carbon monoxide poisoning
- Carboxyhemoglobin
- Cardiac arrhythmias
- Cardiac catheterization
- Cardiac hemolysis
- Cardiac output
- Cardiac rhabdomyoma
- Cardiac tamponade
- Cardiogenic shock
- Cardiology laboratory
- Cardiomegaly
- Cardiomyopathy
- Cardiopulmonary resuscitation (CPR)
- Cardiothoracic ratio
- Cardiotoxicity, in cancer therapy
- Carnitine deficiency
- Caroli disease
- Carotid-cavernous fistulas
- Carpenter syndrome
- Cartilage-hair hypoplasia
- Castleman disease
- Cast syndrome
- Cataplexy
- Cataract
- Cat bites
- Cat eye syndrome
- Catheter-related endocarditis
- Catheter-related peritonitis
- Cat-scratch disease
- Cauliflower ear
- Cautery, for nosebleeds
- Cavernous malformations
- Cavernous sinus syndrome
- Cavernous sinus thrombosis
- Cavernous transformation
- Cavities (dental caries)
- Celiac crisis
- Celiac disease
- Cellulitis
- Cellulitis-adenitis syndrome
- Central apnea
- Central hypothyroidism
- Central hypotonia
- Central line-associated bloodstream infection (CLABSI)
- Central pontine myelinolysis (CPM)
- Central precocious puberty
- Cerebellitis
- Cerebral contusion
- Cerebral edema
- Cerebral hemorrhage
- Cerebral malaria
- Cerebral palsy (CP)
- Cerebral salt wasting
- Cerebral sinovenous thrombosis (CSVT)
- Cerebrocostomandibular syndrome
- Cerumen, impacted
- Cervical adenitis
- Cervical cancer
- Cervical lymphadenopathy
- Cervical sinus, persistence of
- Cervical wattle
- Cervicitis
- Chalazion
- Chamomile
- Chancroid
- Charcot-Marie-Tooth disease
- CHARGE syndrome
- Char syndrome
- Chediak-Higashi syndrome
- Chelation therapy
- Chemical conjunctivitis
- Chemical epididymitis
- Chemotherapy
- Chest pain
- Chest physiotherapy
- Chest roentgenogram (x-ray)
- Chiari malformation
- Chickenpox
- Chikungunya virus
- Child abuse
- Chlamydia ( Chlamydia trachomatis infection)
- Chlamydia psittaci
- Chlamydophila pneumoniae
- Chloride diarrhea, congenital
- Cholangitis
- Cholecystectomy
- Cholecystitis
- Cholelithiasis (gallstones)
- Cholera
- Cholestasis
- Cholesterol, elevated levels of
- Cholinergic urticaria
- Chondroblastoma
- Chondrodysplasia
- Chondrodysplasia punctata 2, X-linked dominant
- Chondrolysis
- Chondromalacia patella
- Chordee
- Chorea
- Chorioamnionitis
- Choriocarcinomas
- Chorioretinitis
- Choroid plexus tumors
- Chronic diarrhea
- Chronic disease
- Chronic granulomatous disease (CGD)
- Chronic hepatitis
- Chronic inflammatory demyelinating polyneuropathy (CIDP)
- Chronic kidney disease (CKD)
- Chronic lymphocytic thyroiditis
- Chronic mucocutaneous candidiasis
- Chronic nonspecific diarrhea of childhood
- Chronic pancreatitis
- Chronic pyelonephritis
- Chronic wasting disease of cervids
- Chuvash polycythemia
- Chvostek sign
- Chylothorax
- Chylous reflux syndromes
- Cigarette/nicotine dependence
- Ciliary dyskinesia
- Circulatory overload, transfusion-associated
- Circumcision
- Cirrhosis
- Citrin deficiency
- Clary sage oil, for impetigo
- Cleft lip and palate
- Clinical reasoning
- Clitoromegaly
- Cloacal exstrophy
- Clogged milk ducts
- Clostridium
- Clostridium botulinum
- Clostridium difficile
- Clostridium perfringens
- Clostridium sordellii
- Clostridium tetani
- Clubfoot
- Cluster headache
- Coagulation disorders
- Coal tar
- Coarctation of aorta
- Coates disease
- Cobalamin (vitamin B 12 ) deficiency
- Cobalamin (vitamin B 12 ) supplementation
- Cocaine
- Coccidioidomycosis
- Cockayne syndrome
- Coenzyme Q10
- Coffin-Lowry syndrome
- Cognitive behavioral therapy (CBT)
- Cognitive biases
- Cohen syndrome
- Coining
- Cold injury
- Cold shock
- Cold urticaria
- Cole-Carpenter syndrome
- Colic
- Colitis
- Collagenous gastritis
- Collagenous sprue
- Coloboma
- Colorado tick fever (CTF)
- Colorectal cancer
- Coma
- Combined oral contraceptive pills (COCs)
- Common variable immunodeficiency (CVID)
- Common warts
- Communication (speech) problems
- Compartment syndrome
- Compensated cirrhosis
- Complementary and alternative therapy
- Complement deficiency
- Complete androgen insensitivity syndrome (CAIS)
- Complete plexus injury
- Complete primary repair of exstrophy (CPRE)
- Complex decongestive physiotherapy (CDP)
- Compulsions
- Concussion
- Condoms
- Conduct disorder
- Condylomata acuminata
- Confusional migraine
- Congenital adrenal hyperplasia (CAH)
- Congenital amegakaryocytic thrombocytopenia
- Congenital anomalies of kidney and urinary tract (CAKUT)
- Congenital cataracts
- Congenital central hypoventilation syndrome
- Congenital chloride diarrhea
- Congenital cutaneous candidiasis
- Congenital cytomegalovirus
- Congenital diaphragmatic hernia (CDH)
- Congenital erythropoietic porphyria (CEP)
- Congenital glaucoma
- Congenital heart disease (CHD)
- Congenital hepatic fibrosis (CHF)
- Congenital hydrocephalus
- Congenital hypothyroidism
- Congenital insensitivity to pain
- Congenital iris ectropion syndrome
- Congenital lymphedema
- Congenital methemoglobinemia
- Congenital milia
- Congenital muscular dystrophy
- Congenital myasthenia
- Congenital nephrotic syndrome
- Congenital rubella syndrome
- Congenital scoliosis
- Congenital syphilis
- Congenital toxoplasmosis
- Congenital tuberculosis
- Congenital varicella syndrome
- Congenital vascular brain lesions
- Congestive heart failure (CHF)
- Conjugated hyperbilirubinemia
- Conjunctival diphtheria
- Conjunctivitis
- Conotruncal anomaly face syndrome
- Conradi syndrome
- Constipation
- Constitutional delay of growth and puberty (CDGP)
- Constitutional language delay
- Constrictive chest wall syndrome
- Constrictive pericarditis
- Contact dermatitis
- Contact vulvovaginitis
- Contraception
- Contrast nephropathy
- Conversion disorder
- Copper accumulation, in Wilson disease
- Copper deficiency
- Copper T380 IUD
- Corneal abrasion
- Corneal haze
- Corneal opacities, in adenovirus infection
- Cornelia de Lange syndrome
- Coronary artery, anomalous
- Coronary artery disease
- Coronary sinus atrial septal defect
- Coronavirus
- Cor pulmonale
- Corrective lenses
- Cortical visual impairment
- Corticosteroids
- Corynebacterium diphtheriae
- Coryza
- Costello syndrome
- Costochondritis
- Cough
- Cough and cold medicines
- Cough etiquette
- Cough syncope
- Cowden syndrome
- Coxsackie virus
- Cracked nipples
- Cradle cap
- Craniofacial dysostosis (Crouzon disease)
- Craniopharyngioma
- Craniosynostosis
- Cretinism
- Creutzfeldt-Jakob disease
- Crigler-Najjar syndrome
- Crimean-Congo hemorrhagic fever
- Crohn disease
- Croup
- Crouzon disease
- Crusted scabies
- Crying
- Cryotherapy
- Cryptococcal immune reconstitution inflammatory syndrome (C-IRIS)
- Cryptococcal infections
- Cryptogenic enteropathy-associated T-cell lymphoma
- Cryptorchidism
- Cryptosporidiosis
- Cupping
- Currarino syndrome
- Cushing disease
- Cushing syndrome
- Cushing triad
- Cutaneous amebiasis
- Cutaneous anthrax
- Cutaneous aspergillosis
- Cutaneous blastomycosis
- Cutaneous candidiasis
- Cutaneous coccidioidomycosis
- Cutaneous diphtheria
- Cutaneous larva migrans
- Cutaneous warts
- Cyanocobalamin
- Cyanosis
- Cyclic neutropenia
- Cyclic vomiting syndrome (CVS)
- Cyclospora
- Cysticercosis
- Cystic fibrosis (CF)
- Cystic hygroma
- Cystinosis
- Cystinuria
- Cystitis
- Cystoisospora belli
- Cytomegalovirus (CMV)