Hip Displasia, CHD or poor hips:
Progressive developmental deformity of hip joints; mild to crippling. Inheritance: polygenic; threshold.
For more information visit the Orthopedic Foundation for Animals.

Hypertrophic Osteodystrophy or HOD:
Painful, swollen joints and bones; fever; may outgrow it but often left with bone deformities; most prevalent in giant breeds; auto immune reaction to vaccines; also associated with oversupplementation. Inheritance is unknown.

Hypomyelinogenesis - Delayed Myelination:
Born with improper nerve covering; tremors and incoordination; may improve and even be normal by one year old. Occurs in six breeds including Weimaraners, Brittany Spaniels and Bernese Mountain Dogs. The prognosis for puppies is good. Affected dogs are born with the myelin sheathing on the nerves underdeveloped. It is similar to Parkinson's Disease in humans, but unlike humans, the dogs are able to regenerate the sheathing with time. Because this insulating coating is missing, impulses sent along the nerves fanned out, missing their intended location and exciting all nerves along the pathway. Once the myelin is regrown, there are no further signs of the problem and puppies go on to lead normal lives.

Hypothyroidism:
Inadequate output of the thyroid hormone causing the coat to thin, becoming coarse, brittle and falling out easily. Other signs that develop gradually are lethargy, obesity, drooping of the eyelids, mental dullness, and irregular heat cycles. Mild thyroid deficiency frequently goes undetected. Diagnosis involves a blood test. Treatment: requires lifetime treatment with thyroid hormone.

Mastocytoma or mast cell tumor:
Malignant and often rapidly spreading nodular skin tumors.

Nictitating Membrane Eversion:
Haw has poor attachments; cartilage is rolled; everts, showing red swelling and curved cartilage.
Inheritance: autosomal recessive (uncertain).

Persistent Right Aortic Arch:
Abnormal artery constricts esophagus half-way to the stomach; vomiting; must be corrected surgically.
Inheritance: polygenic; threshold.

Retinal Atrophy, Generalized Progressive or general PRA:
Retina degenerates; first, night blindness; then total blindness before middle age. Inheritance: autosomal recessive

Syringomyelia, spinal dysraphism; hopper's disease:
Dog stands in a crouch position and hops to move; non-progressive; associated with myelin dysplasias.

Thymic Atrophy:
By one to three months, the dog has stunted growth, wasting and suppurative pneumonia.

Tricuspid Valve Dysplasia:
There is a bad valve between heart chambers which causes other heart problems to develop.

Umbilical Hernia, rupture or "outie":
Bulging of the abdominal contents in sac at umbilicus; common; usually harmless unless it is very large.

Ununited Anconeal Process or elbow dysplasia:
Growth plate in elbow does not fuse; secondary degenerative joint disease: pain and limp; surgical correction required.  The Orthopedic Foundation for Animals has more information on elbow dysplasia. Inheritance: polygenic