Genodermatoses — MCQs

10 questions

A 60-year-old female presents with eczematous itching lesions. Biopsy revealed a subepidermal cleft with Direct Immunofluorescence showing Linear C3 & IgG deposition along the basement membrane zone. What is the likely diagnosis?

Most common mode of inheritance for retinitis pigmentosa is:

A patient has multiple meningiomas, acoustic neuroma and hyperpigmented skin lesions; most likely diagnosis is –

A 15cm hyperpigmented macule on an adolescent male undergoes changes such as coarseness, growth of hair & acne. Diagnosis is?

A 24-year-old male presents with a lesion at the site shown in the image for 4 years. He says it has increased in thickness over the years. Diagnosis is:

An 8-year-old girl has extreme photosensitivity since birth. She has recently been diagnosed with skin cancer. What is the diagnosis?

All are true about this lesion seen in a child with epilepsy except:

A patient presents with the skin finding shown in the image. Identify the most likely diagnosis for this lesion.

Lines of Blaschko are related to?

Q10Medium

A child presents with a history of hypopigmented macules on the back, infantile spasms, and delayed milestones. What is the most likely diagnosis?

Genodermatoses Indian Medical PG Practice Questions and MCQs

Question 1: A 60-year-old female presents with eczematous itching lesions. Biopsy revealed a subepidermal cleft with Direct Immunofluorescence showing Linear C3 & IgG deposition along the basement membrane zone. What is the likely diagnosis?

A. Pemphigus foliaceus
B. Pemphigus Vulgaris
C. Dermatitis herpetiformis
D. Bullous Pemphigoid (Correct Answer)

Explanation: ***Bullous Pemphigoid*** - The presence of **eczematous itching lesions**, a **subepidermal cleft**, and **linear C3 and IgG deposition along the basement membrane zone** on direct immunofluorescence (DIF) are classic diagnostic features of Bullous Pemphigoid. - This autoimmune blistering disease typically affects older individuals and is characterized by antibodies targeting components of the **hemidesmosomes**, specifically BP180 and BP230. *Pemphigus foliaceus* - This condition involves **intraepidermal blistering**, specifically within the granular layer, rather than a subepidermal cleft. - DIF in Pemphigus foliaceus shows **intercellular IgG deposition** in the epidermis, not linear deposition along the basement membrane zone. *Pemphigus Vulgaris* - Pemphigus Vulgaris is characterized by **intraepidermal blistering** above the basal cell layer (**suprabasal clefting**), leading to fragile bullae that rupture easily. - DIF typically reveals **intercellular IgG and C3 deposition** in a "chicken wire" pattern throughout the epidermis, which differs from the linear pattern seen in this case. *Dermatitis herpetiformis* - While Dermatitis herpetiformis is also an autoimmune blistering disease with itching lesions, its characteristic DIF finding is **granular IgA deposition** in the dermal papillae, not linear C3 and IgG at the basement membrane zone. - Histopathology in Dermatitis herpetiformis shows **subepidermal vesicles** with neutrophil infiltration in the dermal papillae, but the direct immunofluorescence pattern is distinct.

Question 2: Most common mode of inheritance for retinitis pigmentosa is:

A. Autosomal dominant
B. X-linked
C. Autosomal recessive (Correct Answer)
D. Mitochondrial inheritance

Explanation: ***Autosomal recessive*** - Retinitis pigmentosa (RP) demonstrates **genetic heterogeneity** with multiple inheritance patterns. - **Autosomal recessive (AR)** inheritance is frequently cited as the most common pattern in many populations, accounting for approximately **50-60% of inherited cases** in various studies. - In AR inheritance, an individual must inherit **two copies of the mutated gene** (one from each parent) to manifest the disease. - Parents are typically asymptomatic carriers, and there is a **25% recurrence risk** with each pregnancy. *Autosomal dominant* - **Autosomal dominant (AD)** inheritance accounts for approximately **30-40% of familial RP cases**. - Only **one copy of the mutated gene** is sufficient to cause the disease. - AD forms typically show **vertical transmission** through generations and often have a **later onset** with milder phenotype compared to AR forms. - Important genes include **RHO** (rhodopsin) mutations. *X-linked* - **X-linked recessive** inheritance represents approximately **5-15% of RP cases**. - This pattern predominantly affects **males**, while females are usually carriers or show milder manifestations. - X-linked RP tends to be the **most severe form** with earliest onset and rapid progression. - The **RPGR** and **RP2** genes are commonly implicated. *Mitochondrial inheritance* - **Mitochondrial inheritance** is **not a recognized pattern** for classic retinitis pigmentosa. - While mitochondrial diseases can cause retinal degeneration, they present as distinct clinical entities (e.g., **NARP, MELAS, Leber's hereditary optic neuropathy**), not as typical RP. - Mitochondrial disorders show **maternal inheritance** and often involve multiple organ systems beyond the retina. **Note:** The relative frequency of inheritance patterns can vary by geographic population and study methodology. Some sources cite autosomal dominant as most common in certain populations. Additionally, **40-50% of RP cases are simplex** (isolated/sporadic) with no clear family history.

Question 3: A patient has multiple meningiomas, acoustic neuroma and hyperpigmented skin lesions; most likely diagnosis is –

A. Neurofibromatosis (Correct Answer)
B. Von Hippel lindau disease
C. Sturge weber syndrome
D. Tuberous sclerosis

Explanation: ***Neurofibromatosis*** - The combination of **multiple meningiomas**, **acoustic neuroma** (specifically bilateral in NF2) [1], and **hyperpigmented skin lesions** (cafe-au-lait spots in NF1, or multiple cutaneous neurofibromas) is highly characteristic of neurofibromatosis. - This presentation suggests either **Neurofibromatosis type 1 (NF1)** with meningiomas (less common but possible) or, more strongly, **Neurofibromatosis type 2 (NF2)** due to the bilateral acoustic neuromas and the presence of meningiomas, with hyperpigmentation being a variable feature [1]. *Von Hippel-Lindau disease* - This disorder is characterized by **hemangioblastomas** of the retina and central nervous system, **renal cell carcinoma**, and **pheochromocytomas**. - It does not typically involve meningiomas, acoustic neuromas, or hyperpigmented skin lesions. *Sturge-Weber syndrome* - This is a neurocutaneous disorder featuring a **port-wine stain (facial nevus flammeus)**, leptomeningeal angioma, and **glaucoma**. - The clinical picture of meningiomas, acoustic neuroma, and hyperpigmented skin lesions does not align with Sturge-Weber syndrome. *Tuberous sclerosis* - This condition is characterized by the growth of numerous **benign tumors in many different organs**, including the brain (tubers, subependymal giant cell astrocytomas), skin (facial angiofibromas, shagreen patches, ash-leaf spots), kidneys (angiomyolipomas), and heart (rhabdomyomas). - While it has **skin lesions** and **brain tumors**, these are distinct from meningiomas and acoustic neuromas, which are not typical features.

Question 4: A 15cm hyperpigmented macule on an adolescent male undergoes changes such as coarseness, growth of hair & acne. Diagnosis is?

A. Melanocytic nevus
B. Becker nevus (Correct Answer)
C. Sebaceous nevus
D. Sebaceous adenoma

Explanation: ***Becker nevus*** - A Becker nevus is a **hyperpigmented patch** that typically appears during adolescence in males, often on the shoulder or upper trunk. - It characteristically becomes **hairy (hypertrichosis)**, more coarse, and can develop acne within the lesion, particularly during puberty due to androgen sensitivity. *Melanocytic nevus* - While melanocytic nevi are hyperpigmented, they generally do not show the characteristic changes of **coarseness, significant hair growth, or acne** within the lesion during adolescence. - They are typically stable in size and texture after initial development, with changes raising concern for **melanoma**. *Sebaceous nevus* - A sebaceous nevus is a **congenital lesion** often appearing as a yellowish-orange, waxy, or bumpy patch, usually on the scalp or face. - It does not typically present as a large, flat hyperpigmented macule that develops hair and acne in adolescence; instead, it may become verrucous or develop tumors in adulthood. *Sebaceous adenoma* - A sebaceous adenoma is a **benign tumor** of the sebaceous glands, usually appearing as a small, solitary, flesh-colored to yellowish papule or nodule, especially on the face. - It is not typically seen as a large, hyperpigmented macule that grows hair and acne over a broad area, as described in the question.

Question 5: A 24-year-old male presents with a lesion at the site shown in the image for 4 years. He says it has increased in thickness over the years. Diagnosis is:

A. Spitz nevus
B. Hyper-melanosis of Ito
C. Becker's nevus (Correct Answer)
D. Congenital melanocytic nevus

Explanation: ***Becker's nevus*** - This lesion typically presents as a **unilateral, hyperpigmented patch** that often appears during childhood or adolescence, increasing in size and thickness with associated **hypertrichosis** (increased hair growth). The image shows a large, irregularly shaped, hyperpigmented area on the torso of a young male, consistent with this description. - The history of increasing thickness over four years further supports **Becker's nevus**, as it is known to progress in thickness and texture, often becoming more indurated and sometimes verrucous. *Spitz nevus* - Spitz nevus is a benign melanocytic nevus typically presenting as a **pink or red, dome-shaped papule or nodule**, commonly on the face or limbs. - It rapidly grows but does not typically present as a large, hyperpigmented patch with associated hypertrichosis like the lesion shown. *Hyper-melanosis of Ito* - Hypermelanosis of Ito (also known as incontinentia pigmenti achromians) is characterized by **streaky or whorled hypopigmented (lighter) skin lesions**, often present at birth or in early infancy. - The image clearly shows a **hyperpigmented (darker) lesion**, which directly contradicts the characteristic hypopigmentation of hypermelanosis of Ito. *Congenital melanocytic nevus* - Congenital melanocytic nevi are typically present **at birth** or become apparent shortly thereafter. While they can be large and hyperpigmented, they usually do not have the prominent feature of increasing thickness and hypertrichosis developing many years later in adolescence or early adulthood in the same way as Becker's nevus. - The description of a lesion appearing during adolescence and increasing in thickness and hairiness for four years makes Becker's nevus a more specific diagnosis than a general congenital melanocytic nevus.

Question 6: An 8-year-old girl has extreme photosensitivity since birth. She has recently been diagnosed with skin cancer. What is the diagnosis?

A. Xeroderma Pigmentosum (Correct Answer)
B. Bloom syndrome
C. Griscelli syndrome
D. Chediak Higashi syndrome

Explanation: ***Xeroderma Pigmentosum*** - This condition is characterized by an extreme sensitivity to **ultraviolet (UV) light** from birth due to defects in **DNA repair mechanisms**, leading to severe sunburns, pigmentary changes (freckles, hypopigmented macules), and a high risk of developing **skin cancers** at a young age. - The history of extreme photosensitivity since birth and the diagnosis of skin cancer in an 8-year-old girl is highly indicative of Xeroderma Pigmentosum. *Bloom syndrome* - Bloom syndrome is an inherited disorder characterized by **stunted growth**, a **photosensitive facial rash (telangiectatic erythema)**, and a predisposition to **various cancers**, including leukemia and lymphomas. - While photosensitivity and cancer risk are present, the extreme skin damage and early onset of specific skin cancers (as opposed to leukemias/lymphomas often seen in Bloom) make Xeroderma Pigmentosum a more fitting diagnosis. *Griscelli syndrome* - Griscelli syndrome is a rare autosomal recessive disorder characterized by **partial albinism**, immunodeficiency, and neurological impairment. - While it involves pigmentary abnormalities, it does not typically present with the extreme photosensitivity or the very early skin cancer development described in the patient. *Chediak Higashi syndrome* - Chediak-Higashi syndrome is an autosomal recessive disorder characterized by **partial albinism**, recurrent pyogenic infections, and neurological abnormalities, due to defective lysosomal trafficking. - This syndrome is not primarily associated with extreme photosensitivity leading to early skin cancers but rather with immunodeficiency and neurological issues.

Question 7: All are true about this lesion seen in a child with epilepsy except:

A. Collagenoma
B. Minor criteria for diagnosis (Correct Answer)
C. Peau d'orange appearance
D. Predominantly seen over trunk

Explanation: ***Minor criteria for diagnosis*** - The presented lesion is a **Shagreen patch**, which is considered a **major diagnostic criterion** for **Tuberous Sclerosis Complex (TSC)**, not a minor one. - A definitive diagnosis of TSC requires two major criteria or one major and two minor criteria. *Collagenoma* - A Shagreen patch is a type of dermal **collagenoma**, characterized by an overgrowth of connective tissue, primarily collagen. - These lesions often feel like **roughened or leathery plaques** on the skin. *Peau d'orange appearance* - The Shagreen patch is often described as having a **'peau d'orange'** or orange peel-like texture due to its irregular surface. - This characteristic texture helps in its clinical identification. *Predominantly seen over trunk* - Shagreen patches are typically located on the **trunk**, especially in the lumbosacral region, as seen in the image. - They are one of the distinctive cutaneous manifestations of TSC.

Question 8: A patient presents with the skin finding shown in the image. Identify the most likely diagnosis for this lesion.

A. Vitiligo
B. Contact leukoderma
C. Piebaldism (Correct Answer)
D. Albinism

Explanation: ***Piebaldism*** - The image shows a **localized patch of depigmentation** on the forehead, characteristic of **piebaldism**. - **Piebaldism** is a rare, congenital autosomal dominant disorder caused by a defect in melanocyte development and migration, resulting in stable, well-demarcated depigmented areas, often with a **white forelock**. *Vitiligo* - **Vitiligo** typically presents as **progressive, acquired macules and patches of depigmentation** that often enlarge over time. - While it can appear on the face, the sharply demarcated, congenital appearance seen here is more consistent with piebaldism. *Contact leukoderma* - **Contact leukoderma** is an **acquired depigmentation** resulting from exposure to chemicals (e.g., rubber, phenols). - It would usually present in areas of direct contact, and the congenital nature of the lesion in the image rules this out. *Albinism* - **Albinism** is a **generalized hypopigmentation** affecting the skin, hair, and eyes due to a defect in melanin production. - The image shows a localized patch of depigmentation, not a widespread lack of pigment characteristic of albinism.

Question 9: Lines of Blaschko are related to?

A. Keratinocytes (Correct Answer)
B. Blood vessels
C. Nerves
D. Bones

Explanation: ***Keratinocytes*** - **Lines of Blaschko** represent the migratory pathways of embryonic cells, primarily **keratinocytes**, in the skin. - These lines are not visible under normal conditions but become apparent in various **genetic skin disorders** where abnormal cells follow these specific patterns. *Blood vessels* - While blood vessels are extensively present in the skin, they do not follow the specific **migratory patterns** described by the Lines of Blaschko. - Their arrangement is more related to **vascular networks** and anatomical supply rather than embryonic cell migration. *Nerves* - **Nerves** in the skin have specific distributions, often following dermatomal patterns, which are distinct from the **Lines of Blaschko**. - Nerve distribution is related to their segmental origin from the **spinal cord**, not the migratory paths of epidermal cells. *Bones* - **Bones** are part of the skeletal system and are not found in the skin, making them unrelated to the **Lines of Blaschko**. - These lines describe epidermal cell migration, which is a feature of the **integumentary system**.

Question 10: A child presents with a history of hypopigmented macules on the back, infantile spasms, and delayed milestones. What is the most likely diagnosis?

A. Neurofibromatosis
B. Sturge-Weber syndrome
C. Tuberous sclerosis (Correct Answer)
D. Nevus anemicus

Explanation: ### Explanation **Correct Answer: C. Tuberous Sclerosis (TSC)** The clinical triad of **hypopigmented macules (Ash-leaf spots)**, **infantile spasms** (West Syndrome), and **delayed milestones** is classic for Tuberous Sclerosis Complex. * **Pathophysiology:** TSC is an autosomal dominant neurocutaneous syndrome caused by mutations in the *TSC1* (Hamartin) or *TSC2* (Tuberin) genes, leading to the overactivation of the mTOR pathway and the formation of hamartomas in multiple organs. * **Dermatological markers:** Ash-leaf spots are often the earliest sign. Other features include Adenoma sebaceum (angiofibromas), Shagreen patches (connective tissue nevi), and periungual fibromas (Koenen tumors). * **Neurological markers:** Cortical tubers and subependymal nodules lead to seizures (infantile spasms) and intellectual disability. **Why Incorrect Options are Wrong:** * **A. Neurofibromatosis:** Characterized by *hyperpigmented* Café-au-lait macules, Lisch nodules, and neurofibromas, rather than hypopigmentation and infantile spasms. * **B. Sturge-Weber Syndrome:** Presents with a Port-wine stain (Nevus Flammeus) in the V1/V2 distribution of the trigeminal nerve, glaucoma, and leptomeningeal angiomas. * **C. Nevus Anemicus:** A localized vascular anomaly presenting as a pale patch due to catecholamine sensitivity. It does not cause systemic neurological symptoms or developmental delay. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest sign:** Ash-leaf spots (best seen under **Wood’s lamp**). * **Most common heart lesion:** Rhabdomyoma (often regresses spontaneously). * **Most common kidney lesion:** Angiomyolipoma. * **Drug of choice for Infantile Spasms in TSC:** Vigabatrin. * **Pathognomonic sign:** Koenen tumors (Periungual fibromas).

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free