A young lady presented with bilateral nodular lesions on shins. She was also found to have bilateral hilar lymphadenopathy on chest X-ray. Mantoux test reveals indurations of 5 mms. A skin biopsy would reveal -
Skin lesions in this patient is Erythema nodosum.
Erythema nodosum, bilateral hilar lymphadenopathy negative Mantoux test is strongly suggestive of sarcoidosis.

Skin biopsy (or biopsy from hilar nodes, conjunctiva, lip, or spleen, intraabdominal nodes) would reveal non-caseating granulomas.

Signs and symptoms of sarcoidosis
Any organ system of the body can be involved. However, lungs with lymph nodes, skin and eye are the three most common sites involved in sarcoidosis.
I.   Lungs with lymph nodes (95%)

Respiratory complaints including a cough and dyspnea are the most common presenting symptoms.
Usually, the infiltrate in sarcoidosis are predominantly an upper lobe process.
There is bilateral hilar lymphadenopathy.

II. Skin (24%-43%)

Erythema nodosum
Maculopapular lesions
Hyper-or hypopigmentation
Keloid formation and subcutaneous nodules
Lupus pernio → Involvement of the bridge of the nose, the area beneath the eyes and cheek. It is diagnostic for a chronic form of sarcoidosis.
Lofgren's syndrome → Erythema nodosum with hilar adenopathy and uveitis.

III. Eye (12-29%)

Uveitis → Cause Photophobia, blurred vision, increased tearing
Retinitis → Cause Photophobia, blurred vision, increased tearing
Pars plastic → Cause Photophobia, blurred vision, increased tearing

IV Non-specific constitutional symptoms are fatigue (most common), fever, night sweat and weight loss. Other organs/systems involved are

Liver                             
Spleen                          
Endocrine → Granuloma can secret 1-25 (OH)2 Vit D which causes hypercalcemia.
Uveoparotid fever → Uveitis + parotitis + VII nerve palsy, it is associated with Heerfordt - waldenstrom syndrome.
Parotid glands           
Heart
Brain (Neurosarcoidosis)
Non caseating Granuloma
Vasculitis
Caseating Granuloma
Malignant cells