Mulibrey nanism is characterized by progressive Growth failure that begins before birth. Infants often have characteristic abnormalities of the head and face including a triangularly shaped face. Yellow discoloration deep within the eyes and other ocular abnormalities may be present but vision is usually normal. Most patients have an enlarged skull (macrocephaly) and a J-shaped sella turcica, which is a Depression in the sphenoid bone at the base of the skull. Because this is where the pituitary gland is located, individuals with MN often have underdevelopment of various endocrine glands that leads to hormone deficiencies. The voice of patients with MN is characteristically high pitched.
Patients may also have symptoms related to overgrowth of the fibrous sac surrounding the heart (non-inflammatory constrictive pericarditis). When constrictive pericarditis presents early (affecting a minority of patients), infants may have a mildly bluish discoloration of the skin (cyanosis). Congestive heart failure of the right heart can also cause abnormal fluid accumulation in the abdomen (ascites) and swelling of the arms and/or legs (peripheral edema). Circulatory problems can progress and lead to failure-to-thrive. Prominent veins in the neck indicate an elevated pressure in the systemic veins that is commonly related to a lack of space in the sac surrounding the heart (pericardial constriction) limiting the filling phase of the heart cycle, and thus leading to fluid accumulation (congestion) in the body. Fibrous tissue in the walls of the lungs (pulmonary fibrosis) decreases the total volume capacity of the lungs.
Enlargement of the liver (hepatomegaly) is another common symptom. In addition, patients often struggle to regulate the breakdown (metabolism) of sugars and fats, potentially resulting in type 2 diabetes, fatty liver and high blood pressure (hypertension). Structural abnormalities of the kidney and urinary tract such as non-cancerous pockets of membranous tissue (cysts) are also observed. However, most patients have normal kidney function. Another persistent kidney complication is a mildly decreased ability to filter the blood (glomerular filtration). Wilms’ tumor, the most common type of cancer originating in the kidney in children, is relatively common (about 8%) and screening is mandatory.
Delayed puberty sometimes occurs accompanied by infrequent or very light menstrual periods. Females have an increased risk for premature ovarian failure and tumors. Both male and female patients show failure of sexual maturation and inability of the sex organs to function properly (hypogonadism) leading to infertility.
Some individuals with MN may have additional physical abnormalities such as an unusually thin shinbone (fibrous tibia dysplasia).
Some children suffer from airway obstruction related to infections or exercise but asthma in adulthood is rare. Large cerebral ventricles in the brain and delayed motor development are uncommon findings. Most affected individuals have normal intelligence.