**Question:** A 25 year old man presents with a kidney stone. He is married to his first Cousin and 6 months earlier, his 8 year - old son had a kidney stone as well. Diagnosis is...

**Core Concept:** Dominantly inherited renal stone disease

**Why the Correct Answer is Right:** In this scenario, the patient and his son both present with kidney stones, and they share a close familial relationship (married to first cousin). Dominantly inherited conditions are those where an affected individual has a 50% chance of passing on the condition to their offspring, regardless of the sex of the parent. In this case, the patient's first cousin marriage might have led to the transmission of a dominant gene for renal stone disease from the patient to his son.

**Why Each Wrong Option is Incorrect:**

A. Recessively inherited condition (e.g., cystinuria) is unlikely given the close familial relationship and the fact that both patient and son have kidney stones.

B. Metabolic abnormalities or dietary factors (e.g., hypercalciuria) might contribute to renal stone formation, but the inheritance pattern contradicts this option.

C. Acute renal colic or renal calculus would be the primary concern for the patient's acute presentation, not the diagnosis itself.

D. Genetic mutations or polymorphisms may play a role in renal stone formation, but the familial nature of the condition and the dominance of inheritance make option A the correct answer.

**Clinical Pearl:** Dominantly inherited renal stone disease should prompt a thorough family history and genetic counseling for the patient and his spouse, considering the risk of future stone formations and potential transmission to future offspring. In this case, the patient's son inherited the dominant gene from his father, leading to the development of renal stone disease.

**Correct Answer:** A (Dominantly inherited renal stone disease)