**Core Concept**
The patient's presentation is suggestive of a systemic disease characterized by scaling skin lesions, lymphadenopathy, hepatosplenomegaly, and lytic bone lesions. This constellation of symptoms points towards a condition involving the immune system and possibly a genetic component.

**Why the Correct Answer is Right**
The patient's symptoms are most consistent with **Seborrheic Dermatitis**. However, the additional findings of lymphadenopathy, hepatosplenomegaly, and lytic bone lesions suggest a more complex underlying condition. The presence of these systemic symptoms, particularly the lytic bone lesions, strongly suggests a diagnosis of **X-linked Severe Combined Immunodeficiency (SCID)**. This condition is characterized by a deficiency in both T and B lymphocytes, leading to impaired immune function and increased susceptibility to infections. The genetic defect responsible for X-linked SCID affects the interleukin-2 receptor gamma chain, which is essential for the development and function of T cells.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while Seborrheic Dermatitis can present with scaling skin lesions, it does not typically cause lymphadenopathy, hepatosplenomegaly, or lytic bone lesions.

**Option B:** This option is incorrect because while Psoriasis can present with scaling skin lesions, it does not typically cause systemic symptoms such as lymphadenopathy, hepatosplenomegaly, or lytic bone lesions.

**Option C:** This option is incorrect because while Eczema can present with scaling skin lesions, it does not typically cause systemic symptoms such as lymphadenopathy, hepatosplenomegaly, or lytic bone lesions.

**Option D:** This option is incorrect because while Contact Dermatitis can present with scaling skin lesions, it does not typically cause systemic symptoms such as lymphadenopathy, hepatosplenomegaly, or lytic bone lesions.

**Clinical Pearl / High-Yield Fact**
The presence of lytic bone lesions in a patient with scaling skin lesions and systemic symptoms should raise suspicion for a systemic disease such as X-linked SCID. This condition requires prompt recognition and treatment to prevent severe consequences.

**Correct Answer:** D. X-linked Severe Combined Immunodeficiency (SCID)