Multiple myeloma (called the M protein; usually IgG or IgA), MGUS (monoclonal gammopathy of undetermined significance), Waldenström's (M protein = IgM) macroglobulinemia
Monoclonal antibody spike
Hypothyroidism
Myxedema
Wegener's and Goodpasture's (hemoptysis and glomerular disease)
Necrotizing vasculitis (lungs) and necrotizing glomerulonephritis
Gout
Needle-shaped, negatively birefringent crystals
Rabies
Negri bodies
Alport's syndrome
Nephritis + cataracts + hearing loss
Alzheimer's disease
Neurofibrillary tangles
Sphingomyelinase deficiency
Niemann-Pick disease
Sheehan's syndrome (pituitary infarction)
No lactation postpartum
CHF
Nutmeg liver
Malignant mesothelioma
Occupational exposure to asbestos
Papillary carcinoma of the thyroid
"Orphan Annie" nuclei
Endocarditis
Osler's nodes
CMV
Owl's eye
Pancreatic cancer (head)
Painless jaundice
Henoch-Schönlein purpura
Palpable purpura on legs and buttocks
Bronchogenic apical tumor associated with Horner's syndrome