(A)

Differential cyanosis refers to the appearance of cyanosis in both lower extremities with a pink right upper extremity. This is seen in patent ductus arteriosus with pulmonary arterial hypertension. The deoxygenated blood in the pulmonary artery goes through the patent ductus arteriosus, empties into the aorta, and flows to the lower half of the body. The upper half of the body continues to get oxygenated blood from the left ventricle.

If the patent ductus enters the aorta below the left subclavian artery, the left arm is pink; if it enters above the left subclavian artery, the left arm...

(A)

Differential cyanosis refers to the appearance of cyanosis in both lower extremities with a pink right upper extremity. This is seen in patent ductus arteriosus with pulmonary arterial hypertension. The deoxygenated blood in the pulmonary artery goes through the patent ductus arteriosus, empties into the aorta, and flows to the lower half of the body. The upper half of the body continues to get oxygenated blood from the left ventricle.

If the patent ductus enters the aorta below the left subclavian artery, the left arm is pink; if it enters above the left subclavian artery, the left arm is blue. Differential cyanosis in a neonate indicates persistent pulmonary hypertension of the newborn and left-heart abnormalities (aortic arch hypoplasia, interrupted aortic arch, critical coarctation, and critical aortic stenosis).

ref: https://www.amjmed.com/article/S0002-9343(13)00282-9/fulltext

(B)

血鐵沉積症(血色素沉著病)

(Hemochromatosis, HFE-Associated Hereditary Hemochromatosis, HFE-HHC)

HFE基因發生突變，導致胺基酸異常，無法調控吸收鐵的蛋白。患者消化道吸收鐵質的調控機制失調，使得大量吸收鐵質，造成體內鐵質無法代謝而累積，逐步損傷身體組織。身體組織大量沉積鐵質，導致心臟、肝臟、內分泌及關節損傷，嚴重的血色素沈著病會引發性無能、不孕、糖尿病、心臟病、骨質酥鬆、肝臟疾病等。

ref: http://www.genephile.com.tw/Tests/hemochromatosis.htm

(C)

characteristics of Marfan syndrome can include:

1. a small lower jaw
2. a high, arched palate (roof of the mouth)
3. deep-set eyes
4. flat feet 
5. a breastbone (sternum) that either protrudes outwards or indents inwards
6. crowded teet

(high arched palate)

ref: https://www.nhs.uk/conditions/marfan-syndrome/symptoms/

(D)

Nail clubbing

Increased entry of megakaryocytes into the systemic circulation. Under normal circumstances in healthy individuals, megakaryocytes that arise from the bone marrow are trapped in the pulmonary capillary bed and broken down before they enter the systemic circulation.

It is thought that in disorders where there is right-to-left shunting or lung malignancy, the megakaryocytes can bypass the breakdown within the pulmonary circulation and enter the systemic circulation. They are then trapped within the capillary beds within the extremities, such as the digits, and release platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF). PDGF and VEGF have growth promoting properties and cause connective tissue hypertrophy and capillary permeability.

ref: https://en.wikipedia.org/wiki/Nail_clubbing