Correct Answer: D. Cat-scratch disease
Cat-scratch disease (CSD), caused by Bartonella henselae, is the classic pathological entity defined by stellate (star-shaped) granulomas. These granulomas are pathognomonic for CSD and represent the hallmark histological finding. The stellate appearance results from central necrosis surrounded by epithelioid histiocytes and lymphocytes arranged in a radiating pattern—resembling a star. This morphology distinguishes CSD from other granulomatous conditions. The organism is transmitted via cat scratches or bites, and the disease presents with regional lymphadenopathy (cat-scratch disease lymphadenitis). In India, CSD is increasingly recognized in urban populations with pet cats, particularly in metropolitan areas. The diagnosis is confirmed by histopathology showing stellate granulomas, and PCR or serology for Bartonella henselae can support the diagnosis. Azithromycin is the preferred antibiotic for systemic disease, though localized lymphadenitis is often self-limited. The stellate granuloma is so characteristic that its presence on histology should immediately prompt consideration of CSD in the differential diagnosis of granulomatous lymphadenitis.
Why the other options are wrong
A. Sarcoidosis — Sarcoidosis produces non-caseating granulomas with tightly packed epithelioid cells and Langhans giant cells, but lacks the central stellate necrosis characteristic of CSD. The granulomas in sarcoidosis are compact and well-formed, not star-shaped. This is a common trap—students confuse 'granuloma' with 'stellate granuloma' and may incorrectly choose sarcoidosis. B. Histoplasmosis — Histoplasmosis (Histoplasma capsulatum) shows caseating granulomas with central caseous necrosis surrounded by epithelioid cells and fibroblasts, but the necrosis is amorphous and central—not radiating or stellate. The organism is seen as small intracellular yeast within macrophages. Histoplasmosis is rare in India and does not produce stellate granulomas. C. Cryptococcosis — Cryptococcosis (Cryptococcus neoformans) typically produces minimal inflammation with sparse granulomatous response, especially in immunocompromised hosts. When granulomas do form, they are non-caseating and lack the stellate architecture. The organism is identified by mucicarmine staining showing a thick capsule. Cryptococcosis does not characteristically produce stellate granulomas.
High-Yield Facts
- Stellate granuloma is pathognomonic for cat-scratch disease caused by Bartonella henselae.
- Central necrosis with radiating epithelioid cells creates the star-shaped appearance that distinguishes CSD from sarcoidosis (non-caseating) and histoplasmosis (caseating).
- Azithromycin is the first-line antibiotic for systemic cat-scratch disease; localized lymphadenitis is often self-limited.
- Regional lymphadenopathy (typically axillary, cervical, or inguinal) follows cat scratch or bite by 1–3 weeks in CSD.
- Bartonella henselae is transmitted via cat saliva on claws; immunocompromised patients (CD4 <50) risk bacillary angiomatosis.
Mnemonics
STAR for Stellate Stelate = Star-shaped → Cat-Scratch disease. The radiating necrosis looks like a star on histology. CSD Granuloma vs Others CSD = Stellate (star-shaped necrosis); Sarcoid = Non-caseating (compact); Histoplasma = Caseating (amorphous). Use the necrosis pattern to differentiate.
NBE Trap
NBE pairs "granuloma" with sarcoidosis to trap students who confuse any granulomatous disease with sarcoidosis. The key discriminator is the stellate (star-shaped) necrosis pattern, which is unique to CSD and absent in sarcoidosis.
Clinical Pearl
In Indian urban practice, a child presenting with painless regional lymphadenopathy after a cat scratch and histology showing stellate granulomas is cat-scratch disease until proven otherwise. Serology (anti-Bartonella henselae IgG) and PCR confirm the diagnosis; most cases resolve spontaneously, but azithromycin accelerates recovery in symptomatic disease.
_Reference: Robbins Ch. 8 (Infectious Diseases); Harrison Ch. 152 (Bartonella Infections)_